ms thesis report

Reducing Energy Consumption & Improving Indoor Environmental Quality through Dynamic Shading

August 2012 Page | 1

Contents Abstract .............................................................................................................................................9

Acknowledgement ........................................................................................................................... 10

1 Introduction .................................................................................................................................. 11

1.1 Executive Summary ..................................................................................................................... 12

1.2 Objectives.................................................................................................................................... 12

1.3 Scope of Research ....................................................................................................................... 12

1.4 Hypotheses ................................................................................................................................. 13

2 Buildings Analysis ...................................................................................................................... 14

2.1 Overview of Commercial Buildings Stock ................................................................................... 14

2.2 Standards, Regulations and Guidelines ...................................................................................... 18

2.3 Contribution from solar shading devices .................................................................................... 19

3 Building Science ........................................................................................................................ 29

3.1 Systems Integration: Whole Building Performance Approach ................................................... 33

3.2 Layered Facade ........................................................................................................................... 36

3.3 Conservation, Efficiency, Active, Passive .................................................................................... 38

4 Commercially Available Products Review ................................................................................... 39

4.1 Case Studies ................................................................................................................................ 41

5 Methodology ............................................................................................................................ 43

5.1 Objectives of the Field Experiments ........................................................................................... 43

5.2 Site Context ................................................................................................................................. 45

5.3 Experiments Setup ...................................................................................................................... 46

5.4 Conditions and considerations during Experiments ................................................................... 55

5.5 Experimental Procedure, Data Sampling and Recording ............................................................ 57

5.6 Limitations................................................................................................................................... 58

5.7 Graph Legends ............................................................................................................................ 59

6 Results and Findings .................................................................................................................. 60

6.1 South East bay Experiments ........................................................................................................ 60

6.1.1 South East bay experiment – OPEN ........................................................................................ 61



6.1.2 South East bay experiment – CLOSED ..................................................................................... 63

6.1.3 South East bay experiment – HORIZONTAL (0ᵒ) ..................................................................... 65

6.1.4 South East bay experiment – ANGLED (45ᵒ) ........................................................................... 67

6.1.5 Comparisons of South East bay experiments ......................................................................... 69

6.1.6 Thermographic Images Analysis ............................................................................................. 76

6.1.7 Recommendations .................................................................................................................. 77

6.1.8 Controls Decision Flow Chart for South East .......................................................................... 78

6.2 South West bay Experiments ...................................................................................................... 80

6.2.1 South West bay experiment – OPEN ...................................................................................... 81

6.2.2 South West bay experiment – CLOSE ..................................................................................... 83

6.2.3 South West bay experiment – HORIZONTAL (0ᵒ) .................................................................... 85

6.2.4 South West bay experiment - ANGLED (45ᵒ) .......................................................................... 87

6.2.5 Comparisons of experiments .................................................................................................. 89

6.2.6 Comparison of base cases between South East and South West ........................................... 95

6.2.7 Thermographic Images Analysis ............................................................................................. 98

6.2.8 Recommendations ................................................................................................................ 100

6.3 West bay Experiments .............................................................................................................. 101

6.3.1 West bay experiment – OPEN, CLOSE, HORIZONTAL (0°), 45°.............................................. 102

6.3.2 Side By Side Experiments Comparison .................................................................................. 104

6.3.3 Radiant Surface Temperature Analysis ................................................................................. 110

6.3.4 Recommendations ................................................................................................................ 111

6.3.5 Controls Decision Flow Chart ................................................................................................ 112

7 Simulation .............................................................................................................................. 114

8 Benefits .................................................................................................................................. 117

8.1 Energy, Health and Productivity Benefits ................................................................................. 117

8.2 Industry Recognition: Achieving LEED NC Version 3 Credits .................................................... 120

9 Recommendations .................................................................................................................. 121

10 Conclusion .............................................................................................................................. 123

11 Future Scope of Work .............................................................................................................. 123



12 Bibliography ............................................................................................................................ 125

Appendix ....................................................................................................................................... 128

List of Figures

Figure 1 : Floor space in office, mercantile, warehouse/storage, and education buildings accounts for 60% of total commercial floor space. ......................................................................................................... 14 Figure 2: 1/3rd of total energy was consumed by office and mercantile buildings. .................................. 15 Figure 3 : Electricity consumption accounts for more than half of the total. Source: (US Energy Information Administration, 2009) ............................................................................................................. 15 Figure 4 : More than half of the energy consumed is for space heating, lighting and cooling. Source : (US Energy Information Administration, 2009) ................................................................................................. 15 Figure 5 : Maximum number of buildings constructed post 1970. ............................................................ 16 Figure 6 : Maximum energy consumed by buildings constructed after 1970. ........................................... 16 Figure 7 : Smart control on automated blinds system that controls harsh sunlight and glare and the ..... 21 Figure 8 : Various exterior shading systems. From left to right : Horizontal overhang, Vertical fins, Combination of overhang and fins, window setbacks, fixed or operable horizontal louvers, Interior blinds. Source: (Liebart A., Herde A.) ......................................................................................................... 21 Figure 9 : Terry Thomas Office Building, Seattle, Washington ................................................................... 22 Figure 10: California Science Academy, California ...................................................................................... 22 Figure 11: Marin Country Day School, Corte Madera, California ............................................................... 22 Figure 12 : David Brower Center, Berkeley, California ............................................................................... 22 Figure 13 : Development in automated shading control, glare control & daylight, dimming light controls in Radiance simulation program. Source: (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002) .................. 25 Figure 14: Montreal office south west test bay .......................................................................................... 26 Figure 15: Interior view of test facade with different shading devices ...................................................... 26 Figure 16: Averaged solar-optical properties at normal incidence of the shading devices used in the experiment .................................................................................................................................................. 26 Figure 17 : Mockup of NYT building test bay .............................................................................................. 27 Figure 18 : Exterior facade of mockup ........................................................................................................ 27 Figure 19: Axonometric view of NYT tower ................................................................................................ 28 Figure 20: Mock up Instrumentation .......................................................................................................... 28 Figure 21: Sun Angles; Top: Annual, Bottom Left: Summer Sun Angles, Bottom Right: Winter Sun Angles. Image Sources: ( CMU Center For Building Performance & Diagnostics) ................................................... 29 Figure 22: Building shapes and forms. Images Source (Los Alamos National Laboratory) ......................... 30 Figure 23: Horizontal External Solar Shading Devices. ............................................................................... 31 Figure 24 : Vertical External Solar Shading Devices. ................................................................................... 32



Figure 25: Egg crate External Solar Shading Devices. ................................................................................. 32 Figure 26: Sources of heat gain (LBNL) ....................................................................................................... 33 Figure 27 :Total energy consumption in high performance buildings ( CMU Center For Building Performance & Diagnostics) ....................................................................................................................... 34 Figure 28: Lighting energy consumption in high performance buildings ( CMU Center For Building Performance & Diagnostics) ....................................................................................................................... 35 Figure 29: Cooling loads in high performance buildings ( CMU Center For Building Performance & Diagnostics) ................................................................................................................................................. 35 Figure 30: Heating loads in high performance buildings ( CMU Center For Building Performance & Diagnostics) ................................................................................................................................................. 35 Figure 31: Intelligent Workplace (Facade System & Interior Systems Integration) ( CMU Center For Building Performance & Diagnostics) ......................................................................................................... 36 Figure 32: Dynamic Facade at Intelligent Workplace, CMU. Source: ( CMU Center For Building Performance & Diagnostics) ....................................................................................................................... 37 Figure 33: Variation of MRT due to solar radiation on clear winter day. (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010) ................................................................................................................................... 44 Figure 34: Climate regions of USA, CBECS 2009 ......................................................................................... 45 Figure 35 : Intelligent Workplace, CBPD, CMU ........................................................................................... 46 Figure 36:Test Bays with external dynamic louvers.................................................................................... 46 Figure 37 : IW Floor plan highlighting test bays used for field experiments .............................................. 47 Figure 38 : South East and South West test bays with blinds and sensors................................................. 48 Figure 39 : West test bays with blinds and sensors .................................................................................... 48 Figure 40: Dynamic External Louvers on East & West façade .................................................................... 49 Figure 41: Clerestory Light Redirection Louvers ......................................................................................... 49 Figure 42: Retro Lux A 80mm ...................................................................................................................... 49 Figure 43: Retro Lux U 50mm ..................................................................................................................... 50 Figure 44: Retro Flex 25mm ........................................................................................................................ 50 Figure 45 : Zone 1 (South East) ................................................................................................................... 51 Figure 46: Zone 2 (South West) .................................................................................................................. 51 Figure 47 : Zone 3 (South East) ................................................................................................................... 51 Figure 48 : Zone 4 (South West) ................................................................................................................. 51 Figure 49: Sheryln's Office (West) ............................................................................................................... 51 Figure 50: Volker's office (West) ................................................................................................................. 51 Figure 51 : Black Globe & HOBO Sensor ..................................................................................................... 52 Figure 52 : Aircuity Sensor .......................................................................................................................... 52 Figure 53 : HOBO Sensor Suite on Rooftop ................................................................................................. 52 Figure 54 : Roof Top Weather Station ........................................................................................................ 52 Figure 55: Nikon Coolpix 5400 and Fish eye Lens ....................................................................................... 54



Figure 56: FLIR Thermographic camera ...................................................................................................... 54 Figure 57: Solar radiation : Sunny Day ........................................................................................................ 56 Figure 58: Solar Radiation : Partly Sunny Day ............................................................................................. 56 Figure 59: South East Test Bay Highlighted ................................................................................................ 60 Figure 60: South & East Bay with Blinds Open ........................................................................................... 61 Figure 61: Zone 1 –East (All blinds Open) .................................................................................................. 61 Figure 62: Zone 1 - South ( All Blinds Open) ............................................................................................... 61 Figure 63: South East Zone – Blinds Closed ................................................................................................ 63 Figure 64: East (All Blinds Closed) ............................................................................................................... 63 Figure 65: South (All Blinds Closed) ............................................................................................................ 63 Figure 66: South & East bay with Blinds Horizontal.................................................................................... 65 Figure 67: East - All Blinds Horizontal (0º) .................................................................................................. 65 Figure 68: South - All Blinds Horizontal (0°) ................................................................................................ 65 Figure 69: South East Zone - Blinds Horizontal ........................................................................................... 67 Figure 70: East - All Blinds 45ᵒ .................................................................................................................... 67 Figure 71: South - All Blinds 45ᵒ .................................................................................................................. 67 Figure 72: IR Image analysis South East bay ............................................................................................... 71 Figure 73: IR Image analysis South East bay .............................................................................................. 71 Figure 74: South East bay - external louvers IR analysis ............................................................................. 76 Figure 75: South West - external vs. internal blinds IR analysis ................................................................. 76 Figure 76: South West - Type of blinds IR analysis ..................................................................................... 76 Figure 77: Controls decision flow chart for South East ............................................................................... 78 Figure 78: South West bay Highlighted ...................................................................................................... 80 Figure 79: South West bay with Blinds Open ............................................................................................. 81 Figure 80: Zone 2 - South (All Blinds Open) ................................................................................................ 81 Figure 81 : Zone 2 - West (All Blinds Open) ................................................................................................ 81 Figure 82: South West Zone - Blinds Closed ............................................................................................... 83 Figure 83: South West - All Blinds Closed ................................................................................................... 83 Figure 84: West - All Blinds Closed.............................................................................................................. 83 Figure 85: South West bay with Blinds Horizontal ..................................................................................... 85 Figure 86: South West - All Blinds Horizontal ............................................................................................. 85 Figure 87: West - All Blinds Horizontal ....................................................................................................... 85 Figure 88: South & West Zone - Blinds 45° ................................................................................................. 87 Figure 89: South : All Blinds 45° .................................................................................................................. 87 Figure 90: West : All Blinds 45° ................................................................................................................... 87 Figure 91: Thermographic image with Blinds Horizontal ............................................................................ 93 Figure 92: Thermographic image with Blinds Closed .................................................................................. 93 Figure 93: Spot measurement : SW - sophisticated light redirection blinds .............................................. 98



Figure 94: Spot measurement : SW - concave up light redirection blinds ................................................. 98 Figure 95: Spot measurement : SE - external blinds closed ........................................................................ 98 Figure 96: Figure 95: Spot measurement : SE - internal blinds closed ....................................................... 98 Figure 97: Spot measurement : SW - external blinds horizontal ................................................................ 99 Figure 98: Spot measurement : SW - internal blinds horizontal ................................................................. 99 Figure 99: Spot measurement : SE - external blinds horizontal .................................................................. 99 Figure 100: Spot measurement : SE - internal blinds horizontal ................................................................ 99 Figure 101: Spot measurement : SE with external louver .......................................................................... 99 Figure 102: Spot measurement : SE without external louver ..................................................................... 99 Figure 103: West test bays Highlighted .................................................................................................... 101 Figure 104: Controls decision flow chart for West ................................................................................... 112 Figure 105 : Number of Buildings and Floor space by Size of Building. .................................................... 114 Figure 106: Number of occupants per building sector (US Energy Information Administration, 2009) .. 117 Figure 107 : Function of three sections of split control blinds , Olbina S. 2012 ....................................... 124 Figure 108 : Split and conventional automated control systems for blinds, Olbina S. 2012 .................... 124

List of Tables Table 1 : Summary Table of Indoor Environmental Quality Standards for Office ...................................... 18 Table 2: Cross sectional study to make a case for application of dynamic façade strategies .................... 20 Table 3 : Types of Exterior & Interior shading devices ............................................................................... 39 Table 4 : Commercially available Products Matrix ...................................................................................... 40 Table 5 : Case Studies Matrix ...................................................................................................................... 42 Table 6 : Sensor Locations in South bays .................................................................................................... 53 Table 7: Sensor Locations in South bays .................................................................................................... 53 Table 8: Sensors Set up in South & West bays ............................................................................................ 53 Table 9 : Outdoor Temperature definitions for field experiments ............................................................. 55 Table 10: Sky Conditions: Solar Radiations (Renewable Energy Concepts : Solar Basics) .......................... 56 Table 11: Thermographic Images for West ............................................................................................... 110 Table 12: Triple Bottom Line Calculations ................................................................................................ 119 Table 13: South East - Experiments result summary ................................................................................ 121 Table 14: South West - Experiments result summary .............................................................................. 121 Table 15: Baseline data assumptions for cost benefit calculations (CMU CBPD BIDS Database) ............ 129 Table 16 : Triple bottom line calculations (CMU CBPD BIDS Database) ................................................... 130



List of Graphs Graph 1 : South East All Blinds Open .......................................................................................................... 62 Graph 2: South East All Blinds Open (Sunny & Partly Sunny Days) ............................................................ 62 Graph 3:South East (All Blinds Closed) ........................................................................................................ 64 Graph 4: South East All Blinds Closed (Partly Sunny & Sunny Day) ............................................................ 64 Graph 5: South East All Blinds Horizontal (0°) ............................................................................................ 66 Graph 6: South East - All Blinds Horizontal (Partly Sunny Days) ................................................................. 66 Graph 7: South East All Blinds 45ᵒ .............................................................................................................. 68 Graph 8 : South East - Blinds at 45ᵒ (Sunny & Partly Sunny day) ................................................................ 68 Graph 9 : South East (Blinds Open vs. Blinds Closed) Outdoor Conditions Comparison – Mild Sunny Days .................................................................................................................................................................... 70 Graph 10: South East - Blinds Open vs. Blinds Closed Comparison ............................................................ 70 Graph 11: South East (Blinds Closed vs. Blinds Horizontal) Outdoor Conditions Comparison – Hot Cloudy Days ............................................................................................................................................................. 72 Graph 12: South East Blinds Closed vs. Blinds Horizontal Comparison ...................................................... 72 Graph 13: South East (Blinds Horizontal vs. Blinds 45) Outdoor Conditions Comparison (Hot Partly Sunny Day) ............................................................................................................................................................. 74 Graph 14: South East - Blinds Horizontal vs. Blinds 45 Comparison ........................................................... 74 Graph 15: South West All Blinds Open ....................................................................................................... 82 Graph 16 : South West All Blinds Open (Sunny & Cloudy day) ................................................................... 82 Graph 17 : South West (All Blinds Closed) .................................................................................................. 84 Graph 18 : South West All Blinds Closed (Sunny & Overcast day) .............................................................. 84 Graph 19: South West - All Blinds Horizontal (0ᵒ) ...................................................................................... 86 Graph 20: South West All Blinds Horizontal (Cloudy days) ......................................................................... 86 Graph 21: South West - All Blinds 45ᵒ ......................................................................................................... 88 Graph 22: South West All Blinds 45 (Sunny Days) ...................................................................................... 88 Graph 23: South West (Blinds Open vs. Blinds Closed) Outdoor Conditions Comparison ( Mild Sunny Day) ............................................................................................................................................................. 90 Graph 24: South West Blinds Open Vs. Blinds Closed Comparison ............................................................ 90 Graph 25: South West (Blinds Closed vs. Blinds Horizontal) Outdoor Conditions Comparison ................. 92 Graph 26: South West - Blinds Closed vs. Blinds Horizontal ....................................................................... 92 Graph 27: South West (Blinds Horizontal vs. Blinds 45) Outdoor Conditions Comparison ........................ 94 Graph 28: South West - Blinds Horizontal vs. Blinds 45 Comparison ......................................................... 94 Graph 29: South East - South West (All Blinds Open) Comparison ............................................................ 95 Graph 30: South East - South West (All Blinds Closed) Comparison .......................................................... 96 Graph 31: South East - South West (All Blinds Horizontal) Comparison .................................................... 96 Graph 32: South East – South West (All Blinds 45ᵒ) Comparison ............................................................... 97 Graph 33: West Bays : All Blinds Open ..................................................................................................... 102



Graph 34: West Bays : All Blinds Closed ................................................................................................... 102 Graph 35: West : All Blinds Horizontal ...................................................................................................... 103 Graph 36: West - Blinds Closed vs. Blinds Open (Ambient temperatures) Comparison .......................... 105 Graph 37: West - Blinds Closed vs. Blinds 45° (Ambient temperatures) Comparison .............................. 105 Graph 38: West - All Blinds Closed (Ambient temperatures) Comparison (With Data Adjustment) ....... 105 Graph 39: Graph 36: West - Blinds Closed vs. Blinds Open (Radiant temperatures) Comparison ........... 107 Graph 40: Graph 37: West - Blinds Closed vs. Blinds 45° (Radiant temperatures) Comparison .............. 107 Graph 41: West - All Blinds Closed (Radiant temperatures) Comparison (With Data Adjustment) ......... 107 Graph 42: West - All Blinds Closed (Ambient temperatures) Comparison (Without Data Adjustment) .. 108 Graph 43: West - All Blinds 45° (Ambient temperatures) Comparison (Without Data Adjustment) ....... 108 Graph 44: West - All Blinds Open (Ambient temperatures) Comparison (Without Data Adjustment) .... 108 Graph 45: West - All Blinds Closed (Radiant temperatures) Comparison (Without Data Adjustment) ... 109 Graph 46: West - All Blinds 45° (Radiant temperatures) Comparison (Without Data Adjustment) ......... 109 Graph 47: West - All Blinds 45° (Radiant temperatures) Comparison (Without Data Adjustment) ......... 109



Abstract

This study analyzes data gathered by conducting a series of field experiments and literature reviews to emphasize and quantify the potential of dynamic external and internal venetian blinds to reduce the energy consumption by lowering the heating and cooling loads in an open plan offices while maintaining the desired task and day light intensity, along with controlling the surface radiant temperatures asymmetry that usually cause thermal discomfort. Glare reduction as an added advantage of the innovative venetian blinds with light redirection properties is also analyzed. Further, the study also identifies the high performance products available in the market currently and presents case studies where these products have been used successfully. The field experiments were done as a part of a Department of Energy funded research project, Energy Efficient Buildings (EEB) Hub. The task included analyzing the impact of blinds in different orientations (East, West and South) on indoor ambient and radiant temperatures with open, closed, horizontal (0°) and 45ᵒ slat positions. Black globe thermometers, HOBO sensors and aircuity sensors were used to collect data including the ambient temperature, radiant temperature, relative humidity and day light levels. A thermographic camera and UGR camera were used to analyze the surface temperatures and brightness contrast respectively. Weather data was collected from a roof top weather station. The research demonstrates that efficient use of solar shadings devices such as internal and external light redirecting blinds with appropriate slat angles with respect to different orientations, seasonal and daily variations can reduce significant amount of heating, cooling and lighting loads while maintaining the desired day light levels in glazed office buildings in Northeast USA.

Keywords:

Glazing, Dynamic solar shading devices, Internal & External Venetian Blinds, radiant surface temperatures, Black Globe thermometer, aircuity sensor, thermographic camera, Energy Plus



Acknowledgement

I would like to extend my heartfelt gratitude to my project mentors Prof. Vivian Loftness, Azizan Aziz and Erica Cochran for their continuous guidance and support throughout the process.

I extend my sincere thanks to the EEB Hub project team members from CMU, Bertrand Lasternas and Flore Marion, for their continuous guidance and assistance for the data collection and analysis.

I would like to thank PhD candidates Omer Karaguzel for guiding me throughout the process of energy simulation in Energy Plus and Rohini Srivastava for her guidance for triple bottom line calculations.

I would also like to thank Barbara Smith and Richard Wilson from Nysan, Hunter Douglas for providing me with the information related to solar shading devices regarding pricing, installation and availability.

Most especially I would like to thank my family and friends for their support and encouragement that helped me in completing this project successfully.



1 Introduction

The building sector has a major share in consuming world’s nonrenewable resources and contributes significantly to the greenhouse gas emissions and climate change. Within the USA, the building sector has a 39% share in total energy consumption (Selkowitz, 2009).This conjecture was verified by the McKinsey & Company 2007 report and it stands in direct contrast with the popular belief about the transportation & other industry sectors being the major contributors. In the USA, 71% of the electricity is consumed in lighting, heating and cooling the buildings. Commercial buildings alone are responsible for 19% of the total energy consumption (Selkowitz, 2009). These staggering numbers suggest that there is an utmost urgency for the buildings to go on an energy diet. To add to this dilemma, a very large percentage of commercial buildings are highly glazed for aesthetics and transparency. The designers aim to provide maximum outside view and access to nature and insist that such glazed buildings would significantly reduce the lighting loads offset by natural day light. Although conceptually the idea is functional, numbers suggest otherwise. While the lighting loads continue to be very high, issues such as visual discomfort due to glare and more global issues such as urban heat island are raising concerns among the environmentalists. The main reason for this gap between the concepts and reality is the lack of effective passive and active design strategies application to optimize the daylight and solar heat gain. The facade, the skin of the building, is the point of maximum thermal exchange between the indoor built environment and the exterior, therefore having a great potential for energy saving. The benefits of dynamic layered facades as compared to static facades and their integration with lighting and thermal control systems are being explored rigorously. Along with the overall energy use benefits, a large body of research has indicated the additional advantages of dynamic facades such as occupant health & comfort and increased productivity.

Europe has experienced several structures built over the last decade that have adopted this technology with proven results showing a reduction in energy consumption. Along with reduced energy consumption, the indoor acoustic quality and aesthetics of the structures have also seen improvement. The building stock in the US too has few examples that have used the layered facade strategy but the application needs to be more wide spread like in Europe. Studies show that the main reason for less aggressive use of these strategies in USA is lack of field tested results, little or no documentation regarding the commercially available products and systems, no third party post occupancy evaluation quantifying the energy benefits and little awareness amongst clients and occupants with respect to return of investments and triple bottom line analysis (Selkowitz S., Aschehoug O., Lee E., 2003) (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002) (Zelena K., Perepelitza M., Lehrer D., 2011). This study aims to quantify the energy savings potential through field experiments conducted by deploying solar shading devices (limited to internal & external venetian blinds) and justify the strategy application with the help of a literature review of best practices across the globe along with commercially available products in USA.



1.1 Executive Summary With the ever increasing number of fully glazed commercial buildings, the need for reduction in energy loads is extremely high. In heating dominant climates, the cooling loads are often neglected in the up gradation proposals and little is done to reduce the heating loads to improve thermal performance of the building along while achieving the desired occupant comfort. The purpose of this study is to quantify the reduction in energy loads especially cooling loads using external and internal dynamic blinds while maintaining the desired indoor daylight intensity with the field experiments and simulation. The experiments done in south east, south west and west orientation over the swing and summer seasons showed 3.94% and 2.24% cooling energy savings due to blinds intervention in south and west respectively.

1.2 Objectives The primary research goal is to quantify the thermal and daylighting benefits of solar shading devices (limited to internal and external venetian blinds) by conducting field experiments to encourage a wide spread application of this strategy in the USA. The analysis specifically includes the effects of deployment of different slats angles of these blinds in different orientations and according to seasonal and daily variations to reduce heating, cooling and lighting loads while maintaining the desired day light intensity. The experiment results are specific to open plan commercial offices and climate zone 5. However, similar methodology can be used in other climate zones for further research. Second aim of the research is to identify the high performance products currently available in the market and generate a detailed case studies matrix of the existing or upcoming buildings where those products are installed successfully showing significantly positive results. Last but not the least; the research goal is to confirm the importance of this strategy with respect to improvement in indoor environmental quality, occupant health and productivity through the literature review.

1.3 Scope of Research This study includes an overview of various types of solar shading devices and focus on analyzing the potential of external and internal dynamic venetian blinds. The proposal begins with a literature review to justify the need for this research topic followed by an investigation of commercially available high performance products. The study then encompasses generation of detailed case studies matrix of the existing or upcoming building projects (national & international best practices) where those products are used and show significantly positive results. Primary focus of this research is generating quantitative data highlighting the energy savings potential through field experiments and simulation done as a part of a DOE funded research Energy Efficient Buildings (EEB) Hub. Finally, the literature review confirms the importance of this strategy with respect to improvement in indoor environmental quality, occupant health and productivity.



1.4 Hypotheses The research aims to identify and prove the following hypotheses: 1. Layered facades with dynamic shading and light redirection devices outperform static facades in lighting & daylighting and reduce overall energy consumption in commercial buildings.

2. Blinds have different effects on thermal and day lighting performance at different angles (open, close, horizontal, 45º) in different orientations depending on daily and seasonal variations.

3. Deploying the blinds with appropriate controls during hot and sunny days in East, West and South orientations in open plan offices helps reduce the operative temperature as well as peak radiant temperature thus reducing thermal discomfort and therefore having a great potential to save energy consumption. They also help to reduce glare by blocking direct solar incidence during mornings in East and afternoons in West thus improving occupant comfort.

4. Accurately angled blinds with respect to orientation maintain desired day light levels indoor even on cloudy days thus reducing the lighting loads.

5. Closed Blinds act as an insulation layer to the facade thus reducing the heating load during nights in winter or swing season as well as reducing cooling loads during summer by maintaining lower temperatures at night. “In 1990 alone, the energy used to offset the unwanted heat losses and gains through windows in residential and commercial buildings cost the United States $20 billion – One fourth of all the energy used for space heating and cooling.” (Anders, 2012)

6. Thermal and visual comfort improves occupant health and productivity.



2 Buildings Analysis This chapter begins with an in depth analysis of various aspects of commercial buildings stock including floor space areas, annual energy consumption, end use distribution, etc. This study is done to justify the dire need for energy conservation in this buildings type. Subsequently, the standards and guidelines for energy efficiency and indoor environmental quality are viewed. Finally, the chapter includes the literature review supporting the hypothesis that there is a great potential for contribution of solar shading devices in reducing energy consumption by lowering the lighting, heating and cooling loads.

2.1 Overview of Commercial Buildings Stock

A detailed analysis of the US Energy Information Administration’s Commercial Buildings Energy Consumption Survey (CBECS), 2003 gives valuable insight that helps make a strong case to make commercial buildings, especially office buildings in USA more energy efficient. CBECS estimated that in 2003 there were 4,859,000 total commercial buildings in USA. Commercial buildings comprise of 71.6 billion square feet of floor space. The survey shows that although the commercial buildings sector is not dominated by a single building type, office buildings are the most common that occupy maximum floor space [Fig 1] and consume maximum energy amongst the rest in commercial sector a lot more even than hospitals. [Fig 2]

Commercial Building Floor Space

Figure 1 : Floor space in office, mercantile, warehouse/storage, and education buildings accounts

for 60% of total commercial floor space. Source: (US Energy Information Administration, 2009)



The survey result shows that electricity, space heating and lighting have staggering numbers in terms of energy consumption in these buildings as seen in Fig 3 and 4.

Figure 3 : Electricity consumption accounts for more than half of the total. Source: (US

Energy Information Administration, 2009)

Figure 4 : More than half of the energy consumed is for space heating, lighting and

cooling. Source : (US Energy Information Administration, 2009)

Figure 2: 1/3rd of total energy was consumed by office and mercantile buildings. Source: (US Energy Information Administration, 2009)



CBECS data shows that the majority (58%) of the office buildings were constructed between the years 1970 – 2003; they account for 63% of the floor space and are responsible for a huge 65% of the total energy consumption in the entire building sector (Fig 5 & 6).

Figure 5 : Maximum number of buildings constructed post 1970.

Source : (US Energy Information Administration, 2009)

Figure 6 : Maximum energy consumed by buildings constructed after 1970.

Source: (US Energy Information Administration, 2009) Further analysis of the data leads to some other major findings as stated below, particularly for lighting strategies in Office Buildings (Park J. et al, 2012) :

More than 76% of all buildings are only artificially lit.

Approximately 60% of office buildings are lit when they are not occupied.

The percentage of building lit when not occupied is statistically significant factor (p < 0.0001) in determining lighting Energy Use Intensity (EUI).The higher the percentage lit when unoccupied, the higher the lighting EUI.



12% of the buildings have reflective window glass.

Less than 10% of buildings have skylights or atriums for lighting.

Less than 1% of the 201 buildings surveyed have sensors or automatic controls for their lighting.

This throws light on the fact that the application of strategies discussed in this report are of utmost urgency to reduce the heating, cooling and lighting loads in this particular sector. Also, the application of these strategies in both new construction as well as retrofits should be considered since majority of the problem is the buildings that already exist.



2.2 Standards, Regulations and Guidelines

Certain design standards and guidelines have been developed to ensure a favorable indoor environmental quality including thermal and visual comfort. This section gives a brief overview of these standards as mentioned in ASHRAE 55 for thermal comfort and IESNA (Illuminating Engineering Society for visual comfort.

Table 1 : Summary Table of Indoor Environmental Quality Standards for Office Source: ( CMU Center For Building Performance & Diagnostics)



2.3 Contribution from solar shading devices

It is important to have a goal to make the entire building with all its systems and components efficient. While reducing energy consumption is extremely beneficial, human dimension should never be forgotten. The indoor environmental quality where people spend more than 90% of their time of the day needs to be addressed. In mid and late nineties, the buildings were designed to block the the sun completely to keep the indoor environment under control. This would help reduce the cooling loads but in turn would block the daylight which could help reduce the lighting loads and also the access to nature for the occupants. Another disadvantage of creating these barriers was that it would also block the sun during winter months where the free solar heat could be useful in offsetting the heating loads.

In heating dominant climates like Pittsburgh, PA there is no need to block the sun permanently as one can reduce the heating load by capturing the free heat from solar gains during winter. However, the sun needs to be kept out in summer to reduce the cooling load. Along with these seasonal variations, there are daily variations depending on the orientation as well as weather conditions. Static solar shading devices fail to respond to both seasonal as well as daily variations and therefore even though they might seem to contribute to energy savings, they play a very little role in enhancing indoor environmental quality with respect to reducing the visual discomfort in form of glare and radiant surface temperatures. Therefore the dynamic solar shading and light redirection devices address not only the thermal comfort, but also successfully convert the glare into useable of glare free daylight .

The following section summarizes the key findings and discussions from the research paper reviews as well as conference proceedings and interviews of people in the industry involved in best practices regarding the contribution of solar shading devices. It can be concluded from the literature review that the idea of dynamic solar shading devices is still new to the US market unlike that in Europe. Although more and more clients and professionals have a good understanding of the positive results of this strategy, lack of technical knowledge, quantitative energy savings data and knowledge of commercially available products together result in less aggressive adoption of these strategies.

"Despite the growing interest in day lighting, "getting it right" remains a challenge. Elegant images in architectural magazines don't automatically translate into sustainable designs with proven comfort and energy performance. Controlling thermal heat loss and gain can be largely addressed with highly insulating glazing technologies on the market today. However, controlling solar gain and managing daylight, view, and glare is at a much earlier stage in terms of cost-effective, available solutions." – Stephen Selkowitz, Building Technologies Head, LBNL



The matrix below shows the cross sectional study making a case for wide spread application of dynamic high performance facade strategies.

Table 2: Cross sectional study to make a case for application of dynamic façade strategies

Sr No Key Findings & Recommendations

(Lee E., Selkowitz S., Bazjanac V.,

Kohler C., 2002)

(Selkowitz S., Aschehoug O., Lee E., 2003)

(Zelena K., Perepelitza M., Lehrer D., 2011)

1 There is a growing interest and change in perspective regarding the need for “intelligent facade”

2 The extent of potential is unrealized due to lack of field testing, third party post occupancy evaluation & no documentation

3 Lot of research and wide application seen in Europe but such examples are rare in USA

4 There is a requirement of better simulation tools & integrated design approach

5 The real challenge of these facades is to reduce heating / cooling loads plus reduce glare while maintaining the user satisfaction

6

Difference in Life Cycle economics between Europe & USA is one of the main reasons for less aggressive implementation of such strategies in USA

Two teams (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002) and (Selkowitz S., Aschehoug O., Lee E., 2003) in their respective researches tried to understand the nature of challenges, potential R&D area to realize full energy savings and daylight potential for high performance facades. Selkowitz et al studied examples of recent projects whereas Lee et al took interviews, studied reports and international reviews regarding various design concepts and their applications. As per the observations of Selkowitz et al study, the first cost investment in these strategies can be offset by savings elsewhere during new construction or retrofits. The authors also state that this requires enhanced automation, better sensors and controls for optimal operations. [Fig 7]. They finally state that clients in USA need to be convinced with real energy savings data for wide application. The most crucial recommendation made by the authors that justifies the topic studied here is that there is a need for field testing of design concepts and technologies as it plays a crucial role in understanding, validating and building confidence in systems performance (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002).



Figure 7 : Smart control on automated blinds system that controls harsh sunlight and glare and the same system allows sun light with reduced glare to offset heating loads.

Source: (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002)

Lee et al and Liebart A. & Herde A. from Somfy Architecture studied few technologies and their applications such as solar control facades (spectrally selective solar control – admit daylight, prevent heat transmission, angular selective solar control – blocks sun, redirects sunlight for diffused daylight), solar filters (overhangs, light shelves) and exterior solar controls that intercept sun before entering the building [Fig 8]. The strongest argument that Lee et al made in their study was that the benefit of improved distribution is not only the increased potential to offset electric lighting requirements with daylight across a greater depth within the perimeter zone but also to improve lighting quality and visual comfort. Lee et al also observed that besides the life cycle economics difference between the USA & EU, the wide adoption of these strategies in the EU can be attributed to higher energy prices, stricter building codes and high expectations regarding quality of work environment and construction. Liebart A. & Herde A. from Somfy Architecture stated that all these light redirection strategies such as light shelves are recommended for above standing view height as the view can either be distorted or impaired. Lee et al mentions in PIER (Public Interest Energy Report) that according to them, the automated venetian blind technology is far less mature with respect to cost effectiveness and broad applicability.

Figure 8 : Various exterior shading systems. From left to right : Horizontal overhang, Vertical fins, Combination of overhang and fins, window setbacks, fixed or operable horizontal louvers, Interior blinds. Source: (Liebart A., Herde A.)



Zelena et al explored best practices in strategies such as massing, orientation, transparency, solar control, ventilation, integration of lighting & HVAC. They concluded that these simple design strategies can be relatively robust design solutions and have a generally predictable impact on energy use and therefore should be pursued whenever possible. They studied the following buildings in North America: (Some of these structures have been studied in the case studies section separately)

Figure 9 : Terry Thomas Office Building, Seattle, Washington

Figure 10: California Science Academy, California

Figure 11: Marin Country Day School, Corte Madera,

California

Figure 12 : David Brower Center, Berkeley, California

Images Source : (Zelena K., Perepelitza M., Lehrer D., 2011) The High Performance Commercial Buildings Conference [1] at Southern California organized by Building Technologies Program, Lawrence Berkeley National Laboratory in 2001 brought forward ideas and concerns of some coveted professionals and researchers working towards the goal of introducing these strategies widely in US and convincing the clients about their benefits.

Most important observations and concerns from these interviews are summarized below: 1. There is a slow but definite shift in the mindset of clients regarding high performance building facades and the need for consideration of occupant comfort. The push is also towards achieving LEED credits that is a driving force for this change. 2. Simple passive and active methods can also be implemented to create the high performance systems.

3. The reason for wide application of these systems in the EU is that unlike the USA is that the acceptable payback is 20-30 years and also, the general rule followed by the planners in EU is around occupant needs.



4. Finally, since there is a dearth of quantifiable data in terms of actual energy savings, these systems are not commonly used in practice in USA and therefore fairly expensive.

Maurya McClintock & Bruce McKinlay from Ove Arup & Partners, California were interviewed during the ASHRAE NetZero Conference in 2009. When asked about their opinion on the reasons for this fast growing trend of high performance facades, they stated that there is a perception today that occupants are the driving force behind the programs and that the architecture & engineering design community thinks that they should provide environmental stewardship. They also pointed out that LEED benchmarking is gaining tremendous recognition because of which the clients show interest in these strategies to get positive LEED rating for their project. Improving indoor and outdoor conditions along with occupant controllability is another factor driving this approach. Finally they mentioned that the only way they convince their clients to pursue this approach is by showing them past integrated building design experiences that resulted in increase in performance at a marginal cost. For example, 0% - 3% increase in capital cost yielded 10% - 15% better performance than stipulated by ASHRAE 90.1-1999 and 5% - 10% increase in capital cost resulted in 20% - 25% better performance.

Kelly Jon Andereck, Environmental Coordinator & Bernie Gandras, Technical Director from Skidmore Owings & Merill (SOM), Chicago, Illinois shared a quote from a white paper by Development Center for Appropriate Technology (DCAT) when asked about the slow pace in USA for adopting these strategies: “… the most commonly stated reasons for denying green alternatives were lack of adequate supporting information (71.4%), and insufficient technical knowledge about the alternative (53.6%).”

Today’s offices demand more dynamic spatial arrangements as the style of working, the technology used, etc. has undergone significant amount of change. Therefore, there is an immediate need to make the building systems more dynamic and responsive to these demands. The Lawrence Berkeley National Laboratory (LBNL) mention in their 2009 report that many building owners are increasingly becoming aware of the potential health and productivity benefits of daylight and the shift in the work pattern with open plan office layouts and technology now encourages more and more highly glazed facades. Along with the transparency, LBNL stated that design teams and owners recognize the problems associated with it, such as, increased visual discomfort from sun penetration and brightness levels exceeding that of the recommended, increased cooling loads, uncertainty of occupant behavior with automation and so on. They therefore conclude that there is now an ever increasing need for better sun control and glare control, and that these solutions must be delivered by dynamic systems whose properties change in response to exterior climate and interior needs. LBNL recognizes that the major challenge for manufacturers is to provide products that meet the increased needs at lower cost and risk to owners.

According to Koo Y. S. Et al, with respect to solar shading devices, blinds have been a common solution. They observed that till very recently, these blinds were operated only manually which failed to address occupant comfort and productivity. Since the occupant behavior is unpredictable, these manually operated blinds were used only to block the direct sun incidence and the slat angles were never changed



even after the sun angles changed or even during the cloudy, overcast days and this almost always blocked the outside view and access to nature along with daylight. Koo Y. S. et al also mention in their study that due to keeping the blinds closed even during cloudy or overcast days, the cooling loads would increase due to overheating of space. This observation directly supports the hypothesis that blinds add an insulation layer to the façade. They also mention that blinds automation has been seen in the last few years but the controls have only focused on eliminating the negative effects of daylight such as glare, while the positive impacts of these solar shading devices have been overlooked. (Koo Y. S., 2009)

“There is a need for controls system for these automated blinds which will help maximize the daylight while avoiding glare thus reducing the lighting load as well as providing occupants with healthy environment with outdoor view depending on the orientation and time of the day. The challenge therefore, is to make the automated blinds system more dynamic; one that is responsive to daily and seasonal variations.” (Koo Y. S., 2009)



Based on these theoretical studies, many researchers have used simulation tools and conducted some field experiments or both to predict and confirm the importance of these solar shading devices with respect to reduction in energy consumption and improved indoor environmental quality in office environments. For example, Lee et al used Radiance simulation program (radsite.lbl.gov) to simulate the dynamic performance of exterior operable shading with fixed exterior sun control elements, for different orientations and the results would be used to further develop shade control strategies. (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002)

Figure 13 : Development in automated shading control, glare control & daylight, dimming light controls in Radiance simulation program. Source: (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002)

Tzempelikos et al included field experiments along with thermal simulation modeling in their study, “Indoor environmental conditions near glazed facades with shading devices.” In this study, their goal was to make a strong case to deploy venetian blinds by proving that even on cold sunny days; the interior glass surface temperature could be quite high thus increasing the operative temperatures to maintain a comfort indoor environment. In their study they discuss about the radiant temperature asymmetry which is one of the prime focus of this report. The results of the experiments suggest that using venetian blinds with the appropriately tilted slats to control the direct solar radiation improve the indoor thermal environment and reduces glare. Their research also suggested that the use of interior shading devices on a cloudy winter day can help reduce the heat loss through facade and thus maintain a comfortable indoor environment without excessive energy consumption. (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010)

For the field experiment, a 32.8 ft (10 m) long south west perimeter zone of a 16 story new office building in Montreal was chosen. The facade was divided into six window sections separated by internal aluminum frames and each section was assigned different types of shading devices. Each section was separated by thick fabric curtains. The climate data was collected from exterior sensors placed next to the facade. Two types of shading devices used were venetian blinds and roller blinds. The solar



radiations incident on the facade were measured using pyranometer, indoor environmental conditions were measured using Indoor Climate Analyzer (ICA). ICA measured the air velocity, humidity, temperature and the plane radiant temperature. Similar to the field experiments in this report, the Mean Radiant Temperature (MRT) was measured using the black globe. The data was collected every 1 minute from the exterior and interior sensors for the entire winter period on sunny as well as cloudy days. The perimeter heating was switched off for the purpose of this experiment so as to understand the impact of outdoor conditions on the indoor environment. To validate the field experiment results, a thermal simulation model was built with climate data inputs, building thermal module and indoor thermal environment modeling.

Figure 14: Montreal office south west test bay

Figure 15: Interior view of test facade with different

shading devices

Figure 16: Averaged solar-optical properties at normal incidence of the shading devices used in the experiment

Images Source : (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010) The field tests showed that venetian blinds performed better than roller blinds, but it highly depended on the tilt of the slats. Tilting the venetian blinds to 45ᵒ showed significant positive impact on the indoor environment than horizontal slats. These results were validated by the thermal modeling results. Simulated interior glass surface temperature followed closely with the measured values, similarly operative temperature was in good agreement with experimental results. This research paper was



helpful in building the experiment set up explained in this report with necessary modifications to fill the gaps of Tzempelikos et al study. For example, conventional venetian blinds were used in their study whereas, in study presented in this report is conducted in test bays which have state-of-the-art light redirecting interior and exterior venetian blinds installed. Also, unlike Tzempelikos et al experiments, this study incorporated South and West orientations experiments for more robust findings.

Lawrence Berkeley National Laboratory (LBNL) was consulted by New York Times in 2003 for their upcoming headquarters in New York City designed as a floor to ceiling glass façade by renowned architects Renzo Piano and Fox & Fowle. LBNL performed field tests in a full scale fully furnished 4500 ft² mockup of the south west corner of the building with two types of automated roller shade products and conventional (0-10V) and Digital Addressable Lighting Interface (DALI) ballasts as daylight control systems. The aim of the field test was to provide credible third-party lighting energy use, control system performance, and visual comfort data. The nine-month monitored study focused on quantifying the synergistic benefits of using automated roller shades with daylight harvesting.

Figure 17 : Mockup of NYT building test bay

Figure 18 : Exterior facade of mockup

Images Sources: (Lawrence Berkeley National Laboratory, 2009)



Figure 19: Axonometric view of NYT tower

Figure 20: Mock up Instrumentation

Images Source : (Lawrence Berkeley National Laboratory, 2009)

In this study, human factors surveys were administered to occupants asked to perform their conventional office tasks. Visualization simulation studies using Radiance were also conducted in parallel to flush out pertinent issues related to the visual environment. Active shades and day lighting management were tested in the above mentioned test bay considering the orientation and daily variations. Lighting energy use, work plane luminance and distribution, various parameters related to visual comfort, control operations, exterior solar conditions, and other environmental parameters were monitored continuously every minute. Monitored data were collected from December 21 to June 21 to capture the full range of solar conditions (Lawrence Berkeley National Laboratory, 2009). Since the experiments were conducted through winter months, the low angle sun penetration that causes concerns of glare was immediately assessed. The roller shades used for the field test had openness factor of 3% with an associated visible transmittance of about 6%.

The study helped to conclude that active shade and daylight management would yield potential benefits to HVAC operations by reducing the cooling and heating loads. In addition, the results from the experiments and simulations showed that up to 60-70% lighting energy from the perimeter zone could be saved with this approach. Overall, 10-30% of total lighting energy could be saved as compared to similar non day lit office building. Simulation and measured data were produced to help the manufacturers optimize zoning, sensor placement and design, and fabric choice. It is unclear from the literature however, if the experiment was conducted in a controlled environment and whether the space was occupied or unoccupied. These considerations can make a large difference in the analysis of the outcome. Also, the main focus of this experiment was lighting energy as compared to both thermal and lighting energy focus presented in this report.



3 Building Science This chapter will describe briefly with diagrams and illustrations the science behind the sun path, solar gain, rejection of unwanted heat, light redirection, its benefits and so on. Further, the concept of whole building performance or systems integration and the benefits of the same will be discussed. The chapter will conclude with a discussion on layered facades and reiteration of the old architecture concepts which need to be revisited and applied to the current building construction.

The figures below show the annual sun angles with summer sun higher and winter sun with its low angles. This knowledge is extremely important during the initial design phases as the building orientation; massing and general configuration should be in relation to these sun angles depending on the function of the space. These decisions could have an everlasting impact on the energy performance of the building.

Figure 21: Sun Angles; Top: Annual, Bottom Left: Summer Sun Angles, Bottom Right: Winter Sun Angles. Image Sources: ( CMU Center For Building Performance & Diagnostics)



The Sun can be a source of free heat during winter, but at the same time can add to the cooling loads during summers if not blocked. With proper light redirection, the sun can not only be blocked effectively but at the same time, the diffused day light can be allowed to fill the interior space. The Sun, therefore, if tackled carefully, can reduce the heating load during winter and offset lighting load all year round. Many studies, for example, (Thayer B., Romm J., Browning W., 1995), prove that day lighting helps improve the health and productivity of the occupants.

There is a trade-off between a compact building form that minimizes conductive heat transfer through the envelope and a form that facilitates daylighting, solar gain, and natural ventilation. (Los Alamos National Laboratory). For example, the cube being the most compact building form would have the least losses and gains through its envelop but if the floor plate is large, then the daylight penetration through this building shape would be minimum beyond a small perimeter zone. On the other hand, the sleek rectangular form would allow the optimization of daylight and natural ventilation and a well-designed day lighting and solar shading system would greatly compensate for the losses and gains through the skin.

Figure 22: Building shapes and forms. Images Source (Los Alamos National Laboratory)

In addition to the building shape and form, additional architectural elements can help in reducing the losses and gains thus reducing the load on the HVAC systems while maintaining a healthy indoor environmental quality. Solar shading devices are such elements which if used appropriately with respect to orientation and daily and seasonal variations can have a great potential to save energy and improve thermal and visual comfort. The solar charts of a specific location where the building is located can help design the solar shading devices accordingly for best results. The different types of external shading devices are seen in the figure below.



Figure 23: Horizontal External Solar Shading Devices. Source: (Scottsdale Green Building Design Program)

During cooling seasons, external window shading is an excellent way to prevent unwanted solar heat gain from entering a conditioned space. Some shading devices can also function as reflectors, called light shelves, which bounce natural light for day lighting deep into building interiors. (Prowler, 2012)



Figure 24 : Vertical External Solar Shading Devices.

Source : (Scottsdale Green Building Design Program)

Figure 25: Egg crate External Solar Shading Devices. Source : (Scottsdale Green Building Design Program)

Interior shades can help in reducing the glare as well as light redirection with today’s state-of-the-art blinds designs. However, they are much less helpful in reducing the solar heat gain.



3.1 Systems Integration: Whole Building Performance Approach

“In a sustainable design, the architecture itself is expected to provide comfort for the occupants” (Los Alamos National Laboratory)

The concept of systems integration is relatively new in terms of practical implementation. Systems integration stems from the idea of whole building performance because scientifically and logically, one system’s performance is either based on or gets affected by multiple building components and systems. For example, within a given space in the building, there are many sources of heat gain, internal as well as external, which increases the cooling load.

Figure 26: Sources of heat gain (LBNL)

Reducing the heat gain from these sources by increasing the efficiency of the systems for example efficient lighting or equipment or by adding systems like solar shading devices would in effect reduce the cooling load. Reduction in cooling load would result in smaller sizes of HVAC equipment, which in turn would require less space within the building and increase the usable area in the building. Energy loads can further be reduced if the systems are linked to each other by controls, for example, automated solar shading devices connected to the sun tracking device being linked to the lighting systems within the building, thus introducing daylight within the building and reducing the lighting load. All these measures will in turn help reduce the overall energy consumption, thus proving to be



extremely cost effective. By integrating the solar shading strategy with lighting within the building there could be many other advantages besides energy savings, for example, glare reduction, access to view for the occupants, etc. thus improving their health and productivity.

The initial investment to have efficient systems integration is sometimes higher than convention and that is one of the reasons why there is no wide spread application of this concept yet. Many studies have shown how the current simulation tools need to evolve to support the concept of systems integration. The Center for Building Performance and Diagnostics (CBPD) at Carnegie Mellon University is located in a state-of-the-art living laboratory called Intelligent Workplace (IW). Numerous energy efficient systems and products are installed in this open place workplace to conduct experiments and test the performance of these technologies. Systems integration with passive and active design strategies is the main concept behind the construction of IW. The systems installed in the IW include Under Floor Air Distribution (UFAD), state-of-the-art solar shading devices including external louvers, internal and external light redirection venetian blinds, a unique water circulation system for heating and cooling, operable windows, daylight & occupancy sensors and so on. Experiments done to date in the IW prove that the huge savings that can be achieved by incorporating these systems would help reduce the period of return on investment tremendously and at the same time make the building climate responsive and environmentally benign. The graphs below a show the huge savings potential of each of the above mentioned systems.

Figure 27 :Total energy consumption in high performance buildings ( CMU Center For Building Performance &

Diagnostics)



Figure 28: Lighting energy consumption in high performance buildings ( CMU Center For Building Performance &

Diagnostics)

Figure 29: Cooling loads in high performance buildings ( CMU Center For Building Performance & Diagnostics)

Figure 30: Heating loads in high performance buildings ( CMU Center For Building Performance & Diagnostics)



3.2 Layered Facade

In the past, the facade was treated as a static element of the building with its primary function to create a barrier between the indoor and outdoor spaces. Architects used this architectural element as a medium to express creativity and make iconic statements through these buildings. Due to this, in the past two decades there were many “climate indifferent” facades. This trend is however changing in the positive direction and the traditional role of the envelope as a filter is being replaced or supplemented with a more active role as an energy collector and transport system. (Selkowitz S., Aschehoug O., Lee E., 2003). Today, as the building usage is evolving rapidly and functions becoming more dynamic, the successful sustainable building solutions need to integrate several strategies like day lighting, solar control plus ventilation instead of any one strategy in isolation. Out of various dynamic facade technologies such as Solar control facades (Spectrally selective solar control, Angular selective solar control, Solar filters, Exterior solar control), Double-skin facades (Heat extraction double-skin facades, Night-time ventilation, Mixed-mode and natural ventilation), Active Facades (Demand-responsive programs, Active load management window strategies) and Daylighting facades (Sunlight redirection, Sky-light redirection) (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002), this report focuses on a combined approach using solar control, day lighting and active load management strategy.

All the field experiments undertaken in this research were conducted in space called A Living Laboratory, “Intelligent Workplace”, at the Center for Building Performance and Diagnostics at Carnegie Mellon University. This space is designed with the systems integration approach as discussed in the earlier section along with the dynamic facade technology.

Figure 31: Intelligent Workplace (Facade System & Interior Systems Integration) ( CMU Center For Building

Performance & Diagnostics)



The facade in this structure is a combination of interior, integral and exterior layer with its strategic components performing several functions such as access to nature, day lighting, shading with light, heat loss heat gain balancing and so on.

Figure 32: Dynamic Facade at Intelligent Workplace, CMU. Source: ( CMU Center For Building Performance &

Diagnostics)



3.3 Conservation, Efficiency, Active, Passive

This section discusses the subtle differences between the conservation and efficiency and active and passive solar strategies and describes how the strategy of implementing interior and exterior solar shading devices fits under these categories.

Conservation vs. Efficiency: There is a thin line between energy conservation and energy efficiency. A lot of times, these two terms are used interchangeably. Although they both have the exact same goal of reduction in energy consumption, there is a difference in the approach of both and if well understood and effectively combined, the benefits can be compounded. In simple words, smart energy practices such as turning off the lights when there is enough daylight & ensuring the water taps are closed properly and there is no water wastage due to dripping can be some basic examples of conservation strategies. Using the energy wisely by using CFLs instead of incandescent lights, eliminating energy waste and installing dual flush toilet to reduce water consumption for example, are efficiency strategies.

“In a broad manner energy efficiency focuses on adjusting directly input requirements for a given output decision whilst energy conservation focuses on reducing overall output decisions, which then reduces the required amount of electricity” (Croucher, July 2011).

Therefore, while it is extremely important to use high efficiency mechanical systems to reduce energy consumption, reducing the energy demands in terms of heating load, cooling load, lighting load etc. by smart building design strategies should also rank very high on the priority list. The introduction of solar shading devices such as internal and/or external blinds discussed in this report can therefore be termed as conservation method.

Active vs. Passive Solar Building Strategies: When building elements are used to collect, store and distribute free solar energy in the form of heat during winter and reject solar heat in summer, thus effectively reducing the heating and cooling loads respectively, can be termed as passive solar building strategies. Using mechanical or electrical devices to control and modulate these dynamic building elements can be termed as active strategies. Similar to conservation and efficiency strategies, if these two strategies are effectively combined, energy consumption can be reduced tremendously. Introducing Solar shading devices appropriately with respect to the orientation and having operable windows for natural ventilation are some examples of the passive method. Adding controls to these solar shading devices to make them responsive to daily and seasonal variations is an example of active intervention.



4 Commercially Available Products Review Regardless of glazing type, shading can improve comfort conditions by decreasing radiant temperature asymmetry and extremes in operative temperature. (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010)

There are different types of shading devices commercially available to serve various purposes such as controlling solar gains, maximizing daylight, reducing glare and so on. Given below is a broad list of shading devices classified as per their possible application.

Table 3 : Types of Exterior & Interior shading devices Exterior shading devices: - Fixed overhangs, light shelves, fins, screens - Green walls - seasonally dynamic shading - Daily dynamic exterior blinds, awnings, brise

soleil - Glass, aluminum, fabric shades

Interior shading devices: - Roll down mesh shades pleated shades - Horizontal & vertical venetian blinds - Light shelf Shutters and screens - Motorized controls for dynamic shading

Light shelves help the daylight to penetrate deeper in the interior space along with elimination of glare. They are therefore helpful in reducing lighting loads in the building. Some manufacturers provide more dynamic light shelves in terms of movability, shapes, finishes, etc. Sun louvers are yet another type of products for external application which can help control the solar gains while maintaining the access to view and maximizing daylight. These louvers can be manufactured in different materials including wood and glass. Roller blinds are used widely in interiors application to control solar gains. However, this strategy has a big disadvantage of the outdoor view being completely blocked. This report focusses on exterior and interior venetian blinds. The conventional blinds were shaped as down turned concave slats with the main purpose of blocking the sun when closed, blocking even the daylight in turn. The next generation of slats has upward concave shape which not only blocks the direct solar incidence but also help in day light redirection. This shape of blinds posed issue of dust accumulation and therefore, some manufacturers have introduced perforations to reduce maintenance. These blinds are still not commonly used in practice and it could be due to lack of knowledge among the designers and clients about it along with higher first cost as compared to conventional blinds or dearth of literature showing possible energy and occupant satisfaction benefits due to these blinds. There are some extremely high performance venetian blinds manufactured by few companies which have unique slats shapes that perform the dual purpose of redirecting the low angle sun rays during winter allowing deeper penetration of daylight and reflecting the high angle sun rays during summer thus reducing the glare. These new generation blinds allow a lot more outdoor view as compared to the conventional blinds. A broad matrix is presented below showing different shading devices from various manufacturers as discussed above and the expected performance from each type. The matrix is not exhaustive either in terms of products available or the manufacturers.

Interior MakroBlind Louvered Shade

Aerofoil Louvers

Dynamic Louvers Brise SoleilSpeciality Louvers

Bright Shelf Retrolux U RetroFlex Retrolux ASpecialist

Venetian BlindsInLighten Light

ShelfVenetian Blind

Hunter Douglas

Hunter Douglas

Hunter Douglas Hunter Douglas

Hunter Douglas Hunter Douglas Retro Solar Retro Solar Retro Solar Levolux Kawneer Colt Unicel

AluminumAluminum, Steel, Wood

Aluminum, Wood, Glass

SteelWood, Glass,

MetalAluminum Aluminum Aluminum Aluminum Aluminum Aluminum Aluminum Aluminum

Fixed

Adjustable / Dynamic (Manual, Automatic, Sensors, Timer,

Computer)

Interior (I)

Exterior (EX) New Construction

RetrofitBoth

4

Perforated slats to permit view even when closed

Highly reflective

mirrored finish

Permits view while reflecting maximum solar incidence back preventing glare

Concave up shape helps

light redirection

Reflects most of solar incidence back before

admitting light indoor

Effortless tilting for cleaning

Day Lighting / Light redirection 5 Glare Reduction

Solar Gain Control 6 100% 100%

Indoor Temperature Control

Quality of light / glare ‐ no glare

8 Easy9 1011

Note : The manufacturers are not from USA alone. This is not an exhaustive list of products available commercially. Similar type of products are available with various manufacturers with slight difference in specifications.

Payback period (years)

Access to nature when fully closed (% of view)

7Occupant Satisfaction

Maintenance factorEase of installation / operation

Cost ($)

Results achieved

Performance Criteria

Manufacturer

Materials

1 Type

2 Location

3 Application

Additional Strategies required / Special Features



4.1 Case Studies This section presents a matrix of case studies worldwide where some of the solar shading devices as described in the earlier chapters were successfully installed. These projects show considerable amount of energy savings with solar shading as one of the green design strategies adopted. These case studies were reviewed and are presented to bring to notice the practical application of the state of the art high performance products that are described in the earlier section. Similar approach of reviewing case studies has been undertaken by few other researchers where they have concluded that many successful building design solutions were the ones that integrated several strategies like daylight, solar control, ventilation etc. instead of just one strategy in isolation. (Lee E., Selkowitz S., Bazjanac V., Kohler C., 2002). The matrix presented here is not exhaustive either in terms of case studies or description of green design strategies adopted, whereas it focuses only on the solar shading strategies pursued.

Besides these real practice applications, there are several simulation and field experiments studies conducted specifically to show the savings possible due to introduction of these solar shading devices. This is an approach similar to the one in this current study. In one such study done by (Lee E., DiBartolomeo D., Selkowitz S., 1998) showed significant energy savings and peak demand reduction with automated venetian blinds and lighting system integration as compared to static venetian blinds with dimmable lighting system. Two side by side experiments were conducted in a fully furnished but unoccupied office in the federal building in California, similar to the setup of the experiments described in this report in subsequent chapters. Along with field experiment, the researchers also conducted a DOE‐2 simulation to realize 16‐26% annual energy savings. Field tests showed a potential of 35‐75% lighting energy savings on a clear sunny day with deployment of automated venetian blinds on south west facade. Since the facility in California had chilled water liquid to air heat exchanger similar to the building presented in this study, the cooling loads conversion to energy use were not made. However, the study showed average daily cooling load reduction of 7 – 15% (45 blinds angle) and 17‐32% (0 Blinds angle) across the seasons by dynamic controls and average lighting energy reductions of 19%‐52% (45 blinds angle) and ‐14 ‐11% (0 Blinds angle). One simulation study by (Hammad F., Bassam Abu Hijleh, 2010) in an office building in Abu Dhabi, a very different climate than the present study aimed at exploring the influence of external venetian blinds on south, east and west facades on overall energy consumption. The researchers found that IES‐VR simulation software predicted 34.02%, 28.57% and 30.31% energy savings for the south, east and west orientations, respectively with the introduction of external dynamic venetian blinds and dimming lighting system. They also stated in their study after detailed analysis that if optimal static angles are used (‐20° for south and 20° for east and west orientations) instead of dynamic system, energy savings were achievable although slightly lower compared to dynamic louvers. The researchers therefore made an argument that if these optimal slat angles were deployed instead of dynamic system due to high first cost, it would still yield in considerable energy savings in that particular climate and could prove to be a good tradeoff between energy savings and investment required for installation.

Project Name Terry Thomas SBL Offices Alley 24 Bank of AmericaLOTT Clean Water

Alliance

Heifer International Headquarters

Manitoba Hydro Interserve Dunelm Mill HQBiodesign Institute,

ASUAddison Wesley

Longman

Function Commercial CommercialMixed Use

(Retail, Office, Residential)Commercial Commercial Commercial Commercial Commercial Commercial Institutional Commercial

Location Seattle, WA Linz, Austria Seattle, WA New York Olympia, WA Little Rock, AR Winnipeg, Canada Leicester, England Leicester, England Tempe, AZ Harlow, UK

Architect Weber Thompson Helmut Schimek, Linzli NBBJ Cook +Fox Miller Hull Patnership LLC

Polk Stanley Rowland Curzon Porter Architects,

Ltd

KPMB Architects CPMG Architects CPMG Architects Lord, Aeck & Sargent C D Partnership

`

View

Recognition LEED GOLD for core and shell and LEED PLATINUM for

commercial interiors

NA LEED Silver LEED Platinum COTE Award LEED Platinum LEED Gold Passivhaus accredition NA LEED Gold NA

NA

Automated louvers

Louvers 4" Motorized

Venetian Blinds with Sun Tracking

2" Chained & Motorized venetian Blinds with sun

tracking

5" & 3" LouversSun shades & Light shelves

Venetian blinds 3" Motorized Venetian Blinds

3" Venetian Blinds

5" Motorized louvers with Sun tracking + Wood

Sun louvers

Solar Shading

Position (Interior / Exterior

)Interior + Exterior Exterior Exterior Interior Interior + Exterior Interior + Exterior Interior + Exterior Exterior Exterior Interior + Exterior Exterior

Manufacturer NA Colt Nysan, Hunter Douglas Nysan, Hunter Douglas Nysan, Hunter Douglas Kawneer Nysan, Hunter Douglas Levolux Levolux Nysan, Hunter Douglas Colt

Special features Operable windows

along with automated louvers

PV cells on louvers NA Motorized or manual NA NA Daylight blinds perforated NA

Manual override, insulatesthe building by reducing night time cooling during winter

Upper half controlled by solar tracking, lower

manual controlNA

% reduction in energy

consumption30% 40% 49% 50% 50% 52% 65% Upto 90% NA NA NA

Data & Image Source

Weber Thompson Colt Hunter Douglas Hunter Douglas Hunter Douglas Kawneer Hunter Douglas Levolux Levolux Hunter Douglas Colt

Note: % reduction in energy consumption represents reduction due to all sustainable design solutions including solar shading devices.NA ‐ Not Available

Type of Solar Shading Device



5 Methodology

The main purpose of this research is to quantify the energy savings with the help of solar shading devices and access the improvement in indoor environmental quality at the same time. Several studies have been conducted in the past which took the approach of energy simulation to determine the benefits of these solar shading devices and help integrate this strategy from the initial design phases for better results. While it is important to acknowledge that these simulation tools are extremely helpful in determining the energy consumption, it must be noted that they fail to address the occupant comfort in terms of glare reduction, reduction in radiant surface temperature asymmetries, health and productivity benefits, etc. There are certain shortcomings in these tools with respect to the development of complex facade systems and systems integration for instance. Advanced simulation tools and aids such as Therm 6 and Window 6 are making way into the research and commercial sectors which could help bring real life accuracy to the building elements. Also, as seen repeated during the literature review, there is a dearth of field studies in the areas of solar shading, day lighting and heating and cooling loads reduction with the help of active - passive strategies.

This study undertakes the measurement based field test approach to determine the potential amount of energy for heating, cooling and lighting that can be saved while maintaining the necessary thermal and visual comfort standards as prescribed by ASHRAE 55 2010 and IESNA 2011 by the use of interior and exterior shading devices for highly glazed facades. Detailed description of the experimental setup within the existing structure is provided in the subsequent sections. The experiments were not performed in a controlled environment and therefore it can be said that the results are conservative figures.

Few studies with a similar approach have been undertaken in the past. Researchers from Lawrence Berkeley National Laboratory (LBNL) have performed few field tests to evaluate the blinds systems with the help of full scale mockups of office spaces. In one such study, they built two side by side full scale offices having automated venetian blinds along with dimmable electric lights in Oakland, California and monitored the lighting energy and cooling load data over one year period. They found 1-22% lighting energy savings and 13-28% cooling load reductions. (Lee E., DiBartolomeo D., Selkowitz S., 1998). In a similar mockup study, LBNL research team evaluated six interior shading systems and four conventional exterior venetian blinds system for a south facing office in Berkeley, California.

5.1 Objectives of the Field Experiments Comprehensive results are presented of the field experiments conducted over a period of five months (March 2012 to July 2012) for full-scale open plan office test bays in a building with layered façade. Adjusting the interior and exterior blinds positions on weekly basis in three orientations including South East, South West, and West and comparing the data with various blind angles was done to find the best



blinds approach on specific orientations depending on daily and seasonal variations to achieve the following: 1. Reduce peak temperatures during the cooling season due to direct solar incidence thus improving

the occupant comfort and reducing the cooling loads by preventing overheating. 2. Reduce heat loss during winter and encourage free cooling at night during summer with blinds

acting as an insulating layer. 3. Encourage free solar heat gain during winter to reduce heating load. 4. Block direct sun at all times to reduce glare. 5. Reduce lighting loads by redirecting daylight thus reducing the use of artificial lighting. 6. Control interior luminance 7. Permit view.

Most importantly, the field experiments were intended to prove that radiant surface temperatures asymmetry especially close to perimeter zone can cause thermal and visual discomfort along with increasing operative temperatures which can be prevented by the appropriately implementing and controlling the shading devices. A simulation study of an office building located in Montreal, Canada was carried out by (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010). From the results of their simulation study, they presented a graph that shows how the mean radiant temperature in the perimeter zones even on a cold but sunny day is up to 15°C higher due to solar radiation than the surrounding surfaces, for the area with an unshaded double glazed uncoated window, which would result in thermal discomfort if not tackled accurately.

Figure 33: Variation of MRT due to solar radiation on clear winter day. (Bessoudo M., Tzempelikos A., Zmeureanu R., 2010)



5.2 Site Context

Figure 34: Climate regions of USA, CBECS 2009

The site is located in Pittsburgh (Latitude: 40ᵒ 20ʹ - Longitude: 79ᵒ 55ʹ) which falls under Climate Zone 5A, the cold/very cold climate region. Pittsburgh experiences 5986 Heating Degree Days and 654 Cooling Degree Days and is therefore a Heating Dominant region. The cooling loads being relatively low throughout the year as compared to the heating loads are often neglected but they can contribute significantly to the annual energy consumption. One of the hypotheses here is that reducing cooling loads can result in significant savings. The experiment results and the extrapolations done in this report are specific to this particular climate and the specific orientations described for the building in the following section. Similar experiments can, however, be done in different setting to generate guidelines for various climates and orientations.



5.3 Experiments Setup

The field experiments were conducted over a period of eight months during Swing season and summer. These experiments were performed in the existing office bays within the Intelligent Workplace (IW) at the Centre for Building Performance & Diagnostics (CBPD), Carnegie Mellon University (CMU) to evaluate the interior and exterior blinds systems for their potential of energy savings and improving indoor environmental quality.

Figure 35 : Intelligent Workplace, CBPD, CMU

Figure 36:Test Bays with external dynamic louvers

The figures below show the floor plan of IW highlighting the test bays in the South and West which where the experiments were conducted. It can be seen that the orientation of the building is 15° east of true South. The two test bay in South and two test bays in West were almost identical to each other with respect to building materials, mechanical systems, furniture and finishes. The test bays in the South were unoccupied whereas the test bays in the West had an occupancy of 1 each.

The IW is primarily designed as an open plan office, with many state of the art systems to facilitate the research going on at the Center. This light weight structure has a layered facade system described subsequently, has an under floor air distribution system and water based heating and cooling systems.



Figure 37 : IW Floor plan highlighting test bays used for field experiments



Figure 38 : South East and South West test bays with blinds and sensors

Figure 39 : West test bays with blinds and sensors

The living laboratory does not have the conventional blinds. As seen in the table below, the blinds are specialized products which not only block the solar incidence but also help in light redirection. Since the test bays are a part of a living laboratory, various high performance products are installed to be tested. With respect to layered façade, louvers and concave up geometry venetian blinds are installed instead of conventional venetian blinds. The following are the types and location of these louvers and blinds: External Louvers, External & Internal Light Redirecting Venetian Blinds and Clerestory Light Redirecting Louvers. Both exterior and interior venetian blinds are retractable and the slat angles can be altered too.



Figure 40: Dynamic External Louvers on East & West façade

Figure 41: Clerestory Light Redirection Louvers

Figure 42: Retro Lux A 80mm

Retro Lux A 80mm. Exterior application.

Manufacturer : Retro Solar Image : (Retro Solar )



Figure 43: Retro Lux U 50mm

Retro Lux U 50mm, Interior Application, Below Clerestory Manufacturer : Retro Solar Image : (Retro Solar )

Figure 44: Retro Flex 25mm

Retro Flex 25mm (Interior) – white bottom, aluminum mirror finish on top. Glare free, ensures color rendition index of > 99. Manufacturer : Retro Solar Image : (Retro Solar )

These blinds are state of the art products with light refraction and redirection as their main properties along with conventional sun blocking. There are at least three types of windows installed in IW, out of which the two types of windows installed in the test bays are as follows : The fixed windows are Viracon selective low e argon filled glazing. The tinted windows in the IW are PPG Hestron low E sungate-azurlite.



The images below show the test south east, south west and west test bays from the interior.

Figure 45 : Zone 1 (South East)

Figure 46: Zone 2 (South West)

Figure 47 : Zone 3 (South East)

Figure 48 : Zone 4 (South West)

Figure 49: Sheryln's Office (West)

Figure 50: Volker's office (West)



The images below show all the sensors that were used during the experiments. Black globe HOBO Sensors were installed at 1.1 m height from the floor to measure the radiant temperature, ambient temperature, relative humidity and day light intensity. Aircuity sensors measured ambient temperature, relative humidity and CO₂ at 2.8m height. Weather data including outdoor dry bulb temperature, global solar radiation and wind speed was acquired from the weather station located on the roof of the building.

Figure 51 : Black Globe & HOBO Sensor

Figure 52 : Aircuity Sensor

Figure 53 : HOBO Sensor Suite on Rooftop

Figure 54 : Roof Top Weather Station



The table below describes the physical characteristics of the sensors with respect to their location and distance from the floor and walls for South test bays.

Table 6 : Sensor Locations in South bays

Sensor Sensor Type Location & Orientation Height from the floor (m)

Distance from exterior wall

1 Hobo Zone 1 - SE 1.1 2.5 2 Hobo Zone 2 - SW 1.1 2.1 3 Hobo Zone 3 - SE 1.0 2.5 4 Hobo Zone 4 - SW 1.0 2.1 5 Near Aircuity Zone 2 - SW 2.43 2.1 6 Near Aircuity Zone 1 - SE 2.43 2.5 7 Hobo Corridor 2.05 2.65 8 Hobo Corridor 2.05 2.65

The table below describes the physical characteristics of the sensors with respect to their location and distance from the floor and walls for West test bays.

Table 7: Sensor Locations in South bays

Sensor Sensor Type Location & Orientation Height from the floor (m)

Distance from exterior wall (m)

1 Hobo Sheryln’s office - W 1.1 0.9 2 Hobo Volker’s Office - W 1.1 1.8 3 Hobo Sheryln’s office - W 1.0 0.9 4 Hobo Volker’s Office - W 1.0 1.8 5 Hobo Sheryln’s office - W 2.0 1 6 Hobo Volker’s Office - W 2.0 1

The table below describes the physical set up of both South and West bays. Table 8: Sensors Set up in South & West bays

Orientation No. of Indoor Blinds

No. of Outdoor Blinds

% glazing

HOBO Sensors

Aircuity Sensors

Test Bay Area (sft)

Zone 1 SE 7 2 55.48 2 3 215.83 (each)

Zone 2 S W 7 2 55.48 2 Zone 3 SW 5 0 63 1 2 Zone 4 SE 4 1 63 1

Sheryln’s Office W 4 1 60.6 3 1 210.00

(each) Volker’s W 4 1 60.6 3 1



The HOBO sensors were calibrated with side by side tests in sunny and cloudy conditions. Other equipment used during the experiments included the following:

1. Nikon Coolpix Camera and Fisheye lens to analyze the Unified Glare Rating using computer software Photolux

2. Thermographic camera which was calibrated by aiming the thermographic camera to the window and then by pointing the hand held therm device.

Figure 55: Nikon Coolpix 5400 and Fish eye Lens

Figure 56: FLIR Thermographic camera



5.4 Conditions and considerations during Experiments Although the test bays were not sealed and were accessible for use, certain conditions were kept constant through the experiments. The experiments are however uncontrolled.

1. External shade (upper fields) always closed SHGC = .25 tvis = .40. This considerably blocks the direct solar incidence on glazing at all times and therefore the result can be considered as conservative.

2. No thermal conditioning 8am - 12pm (HVAC off)

3. Measured: Radiant and Ambient temperature at 1.1m in the center of the test bays and only ambient temperatures on the ceiling 2.6m; Light level at 1.1m.

4. The two test bay in South and two test bays in West were almost identical to each other with respect to building materials, mechanical systems, furniture and finishes. The test bays in the South were unoccupied through all experiments whereas the test bays in the West had occupancy of 1 each through all experiments.

5. Below are the definitions of temperature and sky conditions for the experiments

Table 9 : Outdoor Temperature definitions for field experiments

Hot Average Temp >75ᵒF Comfortable to Warm 75ᵒF > Average Temp > 65ᵒF Mild 65ᵒF > Average Temp > 50ᵒ F Cold Average Temp < 50ᵒF

The sky conditions defined in these experiments are Sunny, Partly Sunny, Cloudy and Overcast. Figures below show the profile of a typical clear sunny day and a partly sunny – partly cloudy day (global solar radiation). More noise seen in the curve as the figure on the right indicates more cloudy or overcast sky conditions. The table below shows how these sky conditions are generally defined with respect to solar radiation.



Figure 57: Solar radiation : Sunny Day

Figure 58: Solar Radiation : Partly Sunny Day

Table 10: Sky Conditions: Solar Radiations (Renewable Energy Concepts : Solar Basics)

sunny, clear sky

sunny, scattered clouds or partly cloudy

cloudy, fog

summer: 600 - 1000 W/m² winter: 300 - 500 W/m²





5.5 Experimental Procedure, Data Sampling and Recording

The experiments were carried out in South test bays during Swing season and then in the West test bays during summer season. As described earlier, the blinds slats positions were changed to arrive at the best strategies for the specific orientation based on daily and seasonal variations. Four blinds slats positions were explored in this research: Blind angle was defined from the horizontal plane, where positive angles allow a ground view from the interior. Open (Blinds fully drawn up), Closed (Fully closed to the mechanical limits of the blinds), Horizontal or 0° (Blinds drawn down and slats open in parallel position to the floor) and 45° (outer edge of the blinds pointing towards the ground). As described earlier, the ambient, radiant and perimeter temperatures along with light intensity measurements were collected from HOBO sensors at 3.6 ft (1.1m) height and on the horizontal surface of the desk top at 5 minutes interval. The outdoor conditions data was obtained from the roof top weather station and HOBO sensor at every 5 minutes interval. The morning time and night time data was analyzed for sunny, cloudy and overcast days during both Swing and summer seasons. Similar experimental procedure was used by (Lee E. D. D., 1998) where they conducted field experiments and analyzed the data for clear sunny and overcast days.

The HOBO sensors were calibrated by keeping them next to each other on sunny and cloudy day and comparing the readings. During the swing season, the experiments were conducted in the two test bays in the South. Experiments with blinds open and blinds closed were conducted in South east and South west bays to calibrate the two bays, so as to conduct side by side experiments with different blinds combination. However, it was found that there was a lot of difference between the two bays due to the influence of East on one bay and West on the other. South West bay also had different readings due to the building self-shading. Therefore, experiments were different blinds slats positions were conducted and analyzed separately for each bay. To normalize and compare the data for different experimental setups, days with similar outdoor conditions with respect to outdoor temperature and solar radiation were identified. A thermographic camera was used to obtain infrared images showing surface temperatures with different blinds positions. These images were taken on a single hot and sunny day and the blinds positions were changed every hour. The infrared images not only gave the surface temperatures but certain extrapolations could be made with those surface temperatures regarding the hypothesis of blinds acting as insulating layer to the facade.

Identifying days with similar outdoor conditions was very difficult during the swing season. To eliminate this day to day climate variability, side by side tests were conducted in two adjacent semi enclosed office spaces facing west. Data collection was similar to that in the South as described earlier. The baseline was then determined followed by various combinations of blinds positions with open, closed, horizontal and 45°. For all experiments, detailed graphs were generated for analysis and the key observations and findings were highlighted. A thermographic camera was used to obtain infrared



images to analyze the surface temperatures with blinds in different positions. Results from these experiments were used in simulation to achieve percentage energy savings.

5.6 Limitations

1. The orientation of two test bays in the South is not the absolute South but a 15ᵒ tilt and therefore the test bays have the influence of East and West orientations. In addition to this, the configuration of the building leads to some self-shading that could hamper the clarity of the results.

2. There are not equal numbers of interior and exterior blinds. Since we have a combination of exterior and interior blinds in both test bays, it is difficult to identify which ones have more impact on reducing cooling load. This, however, is being tackled with the help of infrared images obtained with the help of thermographic camera.

3. The test bays are situated within the existing building which already has external louvers installed as one of the solar shading device. The bays have clerestory with light redirection louvers installed which ensure penetration of daylight even with other blinds closed. The glazing used in the building is double glazed, low E. The blinds installed within the test bays are state of the art light redirection blinds and there are no conventional venetian blinds to compare the performance against. Since the building already has many state of the art installations in place, it can be said that the load reductions seen are extremely conservative.

4. Being an open plan office, there was always some heat dispersion between adjoining bays

5. The results are specific to the building and weather conditions. But the lessons learnt from this study are applicable to similar buildings in other locations with necessary modifications with respect to climate.



5.7 Graph Legends

Following are the line types and colors used in all the graphs in this report.

BLINDS POSITION DENOTATION Open DOTTED

Closed BOLD Horizontal (0°) DASH

45° DASH _ DOT

VARIABLES DENOTATION Ambient Temperature (°F) GREEN Radiant Temperature (°F) PURPLE

Day light Intensity (Surface - LUX) DARK ORANGE Outdoor Temperature (°F) BLUE

Solar Radiation (W/m²) LIGHT ORANGE



6 Results and Findings The conditions for all the field experiments were kept constant as described in the earlier section. The section below shows the comparative data for South East, South West and West test bays with various blinds slats positions. The two zones were compared for weeks by keeping similar blinds positions but a significant difference was found due to the influence of East and West on the two bays. Therefore the blinds positions for the two bays were compared separately.

6.1 South East bay Experiments

The figure below highlights (in yellow) the exact location of the South East test bay in the IW.

Figure 59: South East Test Bay Highlighted



6.1.1 South East bay experiment – OPEN For an entire week all blinds were kept open in zone 1 (SE) and zone 2 (SW), this section showing zone 1 (SE). The ambient and radiant temperatures along with light intensity were recorded. This was established as the base case and the results were compared against different blinds slats positions including all closed, horizontal (0°) and 45º in the subsequent sections.

Figure 60: South & East Bay with Blinds Open

Figure 61: Zone 1 –East (All blinds Open)

Figure 62: Zone 1 - South ( All Blinds Open)

The data collected over six days was plotted as seen in the adjoining graphs. The outdoor temperatures and the solar radiation showed a large range of outdoor conditions throughout the week. A sunny and a partly sunny day data is expanded for further analysis.



Graph 1 : South East All Blinds Open

It is observed that throughout the day, the radiant temperatures are almost always higher than ambient temperatures even on cloudy days [1].

Graph 2: South East All Blinds Open (Sunny & Partly Sunny Days)

Due to influence of the windows in the test bay oriented towards East, direct sun incidence in the mornings causes the radiant temperature to peak up to 7ᵒF more than ambient temperature and day light levels to go much higher than the recommended standards [2]. Due to this radiant temperature asymmetry, the operative temperatures would increase resulting in more cooling load during the mornings to achieve thermal comfort. High day light levels would cause visual discomfort (glare) for occupants.

Solar heat gain would be beneficial during cold, cloudy days [1] as the heating load would be reduced and the day light levels would not cause any glare issue, instead, would help reducing the lighting loads at least from the perimeter zones. This is a matter of further exploration.

[1]

[2]



6.1.2 South East bay experiment – CLOSED For an entire week all blinds were kept closed in zone 1 (SE) and zone 2 (SW), this section showing zone 1 (SE). The ambient and radiant temperatures along with light intensity were recorded.

Figure 63: South East Zone – Blinds Closed

Figure 64: East (All Blinds Closed)

Figure 65: South (All Blinds Closed)

The data collected over seven days was plotted as seen in the graph below. The outdoor temperature and solar radiation showed large range of outdoor conditions over one week. A day with similar outdoor conditions was compared with one day from the previous set of days with all blinds open. The analysis can be found in the comparisons section.



Graph 3:South East (All Blinds Closed)

It is observed that the radiant temperatures are higher than the ambient temperatures only on sunny days. However, there is no peak in radiant temperature even on sunny days as the closed blinds completely block the direct solar incidence [2]. On cloudy or overcast days, both radiant and ambient temperatures followed each other closely. On cold days [1] the indoor temperatures stayed at least 15ᵒF higher than the outdoor temperature. This supports the hypothesis that blinds add insulation to the facade and would thus help in reducing the heating load. This is a matter of further exploration.

Graph 4: South East All Blinds Closed (Partly Sunny & Sunny Day)

Even with the blinds closed on partly sunny and sunny days, the day light levels stayed close to 200lux most of the day which is the recommended day light level as per standards. Therefore, even with blinds closed on sunny days, lighting loads could be reduced without glare issues.

A major drawback with blinds closed is no access to outside view.

[1]

[2]



6.1.3 South East bay experiment – HORIZONTAL (0ᵒ) For an entire week all blinds were kept horizontal (0º) in zone 1 (SE) and zone 2 (SW), this section showing zone 1 (SE). The ambient and radiant temperatures along with light intensity were recorded. The result of this experiment was compared with blinds open and close for further analysis in the subsequent sections.

Figure 66: South & East bay with Blinds Horizontal

Figure 67: East - All Blinds Horizontal (0º)

Figure 68: South - All Blinds Horizontal (0°)

The data collected over seven days was plotted as seen in the graph below. The outdoor temperature plotted in blue and the solar radiation plotted in yellow shows a large range of variations in outdoor conditions over one week.



Graph 5: South East All Blinds Horizontal (0°)

It is observed that the radiant temperatures are always higher than the ambient temperatures. The radiant temperature peaks during the morning up to 2ᵒF as compared to ambient temperature [1]. This, however, is a lot lesser as compared to the blinds open, as seen in the earlier section. Therefore, it can be said that blinds slats at 0ᵒ shave off the radiant temperature peak to a large extent but fails to completely eliminate the temperature rise as well as high day light levels which would cause discomfort due to glare [1].

Graph 6: South East - All Blinds Horizontal (Partly Sunny Days)

The daylight levels in the morning are way above the recommended standards and pose an issue of glare. However, it is observed that after the peak during the morning, the light levels stay very close to the recommended standards, which in turn would greatly help in reducing the lighting loads for a major portion of the day.

[1]



6.1.4 South East bay experiment – ANGLED (45ᵒ) For an entire week all blinds were kept horizontal (45°) in zone 1 (SE) and zone 2 (SW), this section showing zone 1. The ambient and radiant temperatures along with light intensity were recorded. The result of this experiment was compared with blinds open, close and horizontal for further analysis in the subsequent sections.

Figure 69: South East Zone - Blinds Horizontal

Figure 70: East - All Blinds 45ᵒ

Figure 71: South - All Blinds 45ᵒ

The data collected over fourteen days was plotted as seen in the graph below. The outdoor temperature plotted in blue and the solar radiation plotted in yellow shows a large range of variations in outdoor conditions over one week.



Graph 7: South East All Blinds 45ᵒ

It is observed that the radiant temperatures follow the ambient temperatures closely except for the 5ᵒF peak around 9am in the morning due to the influence of East [1]. This data is compared with blinds open, closed and horizontal in the subsequent section. However, from this data it may be said that blinds at 45ᵒ angle may not be extremely efficient during the mornings in the East orientation, as this may cause glare issues along with thermal discomfort.

Graph 8 : South East - Blinds at 45ᵒ (Sunny & Partly Sunny day)

It is also observed that except for mornings, the daylight levels were maintained to the recommended standards with blind slats angled at 45ᵒ on sunny days as well as on cloudy days which could help reduce lighting loads for the major portion of the day.

[1]



6.1.5 Comparisons of South East bay experiments Comparisons were made within the South East bays with different blinds slats angles. The following are the list of comparisons made. Each of these will be discussed in detail in this section. Similar comparisons are made for South West bays in the later section.

1. South East – Blinds Open vs. Blinds Closed 2. South East – Blinds Open vs. Blinds Horizontal (0°) 3. South East – Blinds Open vs. Blinds 45° 4. South East – Blinds Closed vs. Blinds Horizontal 5. South East – Blinds Closed vs. Blinds 45° 6. South East – Blinds Horizontal vs. Blinds 45°

Two days with similar outdoor conditions from each of the combination were identified (out of seven days for each blinds position) and the data was compared and analyzed. A thermographic camera was used to compare the window surface temperatures due to different blind positions. The infra-red images show a range of surface temperatures with or without blinds and blinds with different slat positions. The color palette of purple to orange to yellow are used in the images to show the range of the temperatures from cooler to warmer respectively, that means, the area in purple is cooler than the one in orange and the area in orange hue is cooler than the area in yellow. Nikon camera with fisheye lens was used to capture images of the test bays with different blinds slats positions, which were analyzed in Photolux, a software designed to generate the luminance map to analyze the unified glare ratio on surfaces. The exposure time and aperture size of the digital camera were manually changed. Glare was established based on the standards mentioned in table 1 of this report. Recommendations in the subsequent chapter were made based on the data comparison from all the above mentioned methods. Similar methodology was used to analyze South West test bays results and generate recommendations which can be found in the subsequent chapters.

The highlighted comparisons could not be made since comparable days with similar outdoor conditions could not be found and these should be carried out in the future research.



1. South East – Blinds Open vs. Blinds Closed

The experiments with these blinds settings were done in variable spring temperatures and sun conditions. As mentioned earlier, two days with similar outdoor conditions were identified and compared out of one week of blinds open and one week of blinds closed as seen in the graph below. The outdoor conditions used to find similarity included outdoor temperature and solar radiation.

Graph 9 : South East (Blinds Open vs. Blinds Closed) Outdoor Conditions Comparison – Mild Sunny Days

The graph below shows the comparison between blinds open and blinds closed in South East bays.

Graph 10: South East - Blinds Open vs. Blinds Closed Comparison



From the above graph, following points can be concluded:

1. Interior ambient temperatures without conditioning ranged from 68-74°F with daylight levels of 100-150 lux when blinds were closed.

2. Closing blinds on a day with temperatures rising from 50-65°F (8 am-6 pm), will maintain 2°F cooler morning indoor ambient air temperatures (may not be beneficial during heating season), and 8°F cooler peak radiant temperature (reduces radiant temperature asymmetry) conditions during the morning as compared to blinds open.

3. Opening blinds at night allowed 3°F of free cooling through radiation to the night sky. This observation supports the hypothesis that the blinds act as an insulation layer to the façade. This is a matter of further exploration.

The infra-red images taken by thermographic camera shows the surface temperatures on the South East bay with blinds open and blinds closed. It can be seen that with blinds closed, the range of surface temperatures is 2°F lesser than with blinds open. The top portion of the window with blinds open show cooler temperature than the rest due to the presence of external louvers as a shading device [1]. With blinds closed in the afternoon, the surface temperatures were warmer [2] which supports the hypothesis of blinds acting as insulating layers and capturing heat. The images were taken during different times of the day and therefore the accuracy of comparison is limited.

Figure 72: IR Image analysis South East bay

Figure 73: IR Image analysis South East bay

2. South East – Blinds Open vs. Blinds Horizontal (0°) & 3. South East – Blinds Open vs. Blinds 45° experiments results not available.

[1]

[2]



4. South East – Blinds Closed vs. Blinds Horizontal The graph below shows the two similar days identified for comparison for blinds closed and blinds horizontal in the South East bay.

Graph 11: South East (Blinds Closed vs. Blinds Horizontal) Outdoor Conditions Comparison – Hot Cloudy Days

The graph below shows the comparison of data for blinds closed and blinds horizontal. Since the outdoor temperature with blinds horizontal was higher during at the beginning of the day as seen in the graph above, the difference between the indoor temperatures during that time of the day was very high as seen in the graph below and therefore not compared.

Graph 12: South East Blinds Closed vs. Blinds Horizontal Comparison

[1]



The following conclusions can be drawn from the comparison: 1. There is a slight peak in radiant temperature during morning [1] with blinds horizontal unlike blinds

closed even on a cloudy day. This shows that blinds horizontal during morning can still cause surface temperature asymmetry which can be avoided by blinds closed.

2. Daylight levels with blinds horizontal were higher than the recommended standards unlike blinds closed. Blinds closed would therefore reduce the problem of glare but at the cost of 100% blockage of view.

3. The outdoor temperatures with blinds horizontal dropped slightly as compared to blinds closed. The indoor temperatures with blinds horizontal dropped at least by 2°F as compared to blinds closed. This supports the hypothesis regarding blinds as insulation to the facade.

5 . South East – Blinds Closed vs. Blinds 45° experiments results not available.



6. South East – Blinds Horizontal vs. Blinds 45 The graph below shows the two similar days identified for comparison for blinds horizontal (0ᵒ) and blinds 45ᵒ in the South East bay.

Graph 13: South East (Blinds Horizontal vs. Blinds 45) Outdoor Conditions Comparison (Hot Partly Sunny Day)

The graph below shows the comparison of data for blinds horizontal and blinds 45. The comparable days were 6th May and 24th May 2012. Since 6th May was a weekend with no occupancy, indoor temperatures were uniformly raised by 1.89° F to reflect average contribution of week day internal gains.

Graph 14: South East - Blinds Horizontal vs. Blinds 45 Comparison



The following conclusions can be drawn from the comparison: 1. Field studies reveal that setting south and east blinds to a better shading position at a 45o tilt will

reduce air temperatures by 1-2oF as compared to blinds set horizontally. 2. Daylight levels were maintained at least at 200 lux for effective ambient lighting with blinds 45ᵒ

whereas the daylight levels with blinds horizontal were extremely high especially during the morning. Some standards require at least 500 lux for ambient lighting but from experience through these field experiments and surveys it has been noted that people can work comfortably with 200 lux.

3. Radiant temperature differences were even more substantial which will also have energy and comfort impacts.



6.1.6 Thermographic Images Analysis

Figure 74: South East bay - external louvers IR analysis

External louvers keep the upper band of the window cooler than the rest of the area without any shading device

Figure 75: South West - external vs. internal blinds IR analysis

Exterior blinds keep the surface temperatures cooler than the interior blinds

Figure 76: South West - Type of blinds IR analysis

Advanced light redirection blinds help maintain cooler surface temperatures than the concave blinds



6.1.7 Recommendations

From all the comparisons made in the earlier section for South East bays, the following recommendations can be made based on the observations while keeping in mind the limitations of the field experiments.

1. Since any angle of blinds slats fail to prevent the peaks in radiant temperatures and glare during the mornings, blinds should remain closed during morning to minimize the surface temperature asymmetry if the room is occupied. However, access to outside view would be compromised 100%; therefore, as soon as the sun moves away from the window plane, the blinds slats angles must be changed.

2. Blinds must be kept open on cold sunny days past morning to reduce the heating load with the help of free solar heat gain.

3. From the experiments it has been observed that blinds provide some amount of insulation in horizontal, closed and 45ᵒ slat angles positions. Therefore during the heating season, the blinds should remain closed at night to reduce heat loss. During the cooling season, the blinds should remain open or horizontal during nights depending on the outdoor temperature to reduce cooling loads.

4. Based on the observations of infra-red images taken from thermographic camera in both South East & South West bays, it is recommended to have exterior blinds to block the solar incidence on the windows and maintain cooler temperatures. Interior blinds would help light redirection and reduce glare but they do not help in reducing the surface temperature. Light redirection blinds are recommended over conventional venetian blinds to maintain cooler surface temperatures while maintaining desired day light levels and preventing glare.



6.1.8 Controls Decision Flow Chart for South East

Based on the observations from the field tests regarding indoor ambient and radiant temperatures along with day light intensity, a controls decision flow chart was developed. Occupancy has been considered in the decisions in this flow chart assuming that occupancy sensors would be installed which was not a part of the field experiment.

Figure 77: Controls decision flow chart for South East

The items on the left hand side that include solar radiation, luminance levels, outdoor and indoor temperatures are the decision variables to address the seasonal variables. There are different controls logics for morning, afternoon and night to address the daily dynamics. As per the chart seen below, in case of sunny hot morning, the blinds should be kept closed to reduce the cooling load and glare. However, in case of sunny cold days, the blinds can be kept open to take the benefit of free solar heat



gain thus reducing the heating load, if there is no occupancy. If the room is occupied then the blinds will have to be kept closed so as to avoid glare issues. If the morning is cloudy or overcast with outdoor temperatures ranging between the comfortable band, the blinds can be kept open or horizontal, as there would be no excess heat gain or loss and no glare issue too. The rest of the controls decision flow chart should be read in the similar way.

Similar flow chart was developed for the West bay and is explained in the subsequent sections. The later section also describes the equipment needed to make the best use of these control logics for reducing energy consumption and increasing occupant comfort.



6.2 South West bay Experiments

The figure below highlights (in yellow) the exact location of the South East test bay in the IW.

Figure 78: South West bay Highlighted



6.2.1 South West bay experiment – OPEN

For five days all blinds were kept open in zone 1 (SE) and zone 2 (SW), this section showing zone 2 (SW). The ambient and radiant temperatures along with light intensity were recorded. This was established as the base case and the results were compared against different blinds slats positions including all closed, horizontal (0º) and 45º in the subsequent sections.

Figure 79: South West bay with Blinds Open

Figure 80: Zone 2 - South (All Blinds Open)

Figure 81 : Zone 2 - West (All Blinds Open)



The data collected over five days was plotted as seen in the graph below. The outdoor temperature and the solar radiation showed large range of variations in outdoor conditions. Sunny and cloudy days were expanded for further analysis.

Graph 15: South West All Blinds Open

It is observed that the radiant temperatures are always higher during the day than the ambient temperatures even on cloudy days. The influence of West orientation is seen during the sunny afternoons as there is a peak in the radiant temperatures of almost 7ºF than the ambient temperatures as seen in graph below [1].

Graph 16 : South West All Blinds Open (Sunny & Cloudy day)

With the maximum outdoor temperatures reaching 75ºF, the maximum ambient temperature observed was 78ºF and the maximum radiant temperature was 86º F on sunny days. The maximum difference of 8ºF was seen between ambient and radiant temperature during the afternoon on a sunny day even though the outdoor temperature was as low as 64ºF as seen in graph above [1]. It can also be seen that the daylight levels during the afternoons is very high and is a potential source of glare that causes visual discomfort.

[1]



6.2.2 South West bay experiment – CLOSE

For an entire week all blinds were kept closed in zone 1 (SE) and zone 2 (SW), this section showing zone 2 (SW). The ambient and radiant temperatures along with light intensity were recorded.

Figure 82: South West Zone - Blinds Closed

Figure 83: South West - All Blinds Closed

Figure 84: West - All Blinds Closed

The data collected over five days was plotted as seen in the graph below. The outdoor temperature and the solar radiation showed large range of variations in outdoor conditions. Sunny and overcast days were expanded for further analysis.



Graph 17 : South West (All Blinds Closed)

It is observed that the radiant temperatures and ambient temperatures follow each other closely on all days including sunny as well as cloudy days. No peak in radiant temperature was observed even during afternoons. Most of the days during this test maintained cooler temperatures, much below 65ºF. In that situation, the indoor temperatures were always at least 5ºF warmer.

Graph 18 : South West All Blinds Closed (Sunny & Overcast day)

The graph above also shows that even with the blinds completely closed the daylight levels are above 200 lux on a sunny day which is more than the recommended standard. But on overcast day, even with blinds closed the daylight levels were sustained close to 200lux. This supports the hypothesis that desired daylight levels indoors can be maintained with blinds closed.



6.2.3 South West bay experiment – HORIZONTAL (0ᵒ)

For an entire week all blinds were kept horizontal (0°) in zone 1 (SE) and zone 2 (SW), this section showing zone 2. The ambient and radiant temperatures along with light intensity were recorded. The result of this experiment was compared with blinds open and close for further analysis in the subsequent sections.

Figure 85: South West bay with Blinds Horizontal

Figure 86: South West - All Blinds Horizontal

Figure 87: West - All Blinds Horizontal

The data collected over seven days was plotted as seen in the graph below. The outdoor temperature and the solar radiation showed large range of variations in outdoor conditions. Two cloudy days were expanded for further analysis.



Graph 19: South West - All Blinds Horizontal (0ᵒ)

The graph below shows that the radiant temperatures are slightly higher throughout the day as compared to ambient temperatures, however during the afternoons the difference increases. As compared to the variations in outdoor temperatures, the horizontal blinds seem to smoothen the indoor temperatures and especially the radiant temperature peaks in the afternoons in West as seen with blinds open.

Graph 20: South West All Blinds Horizontal (Cloudy days)

It is observed that the daylight levels are extremely high than the recommended comfort standards, both IESNA as well as the observed 200 lux daylight level that occupants are comfort within, with blinds in horizontal position especially in the afternoons.



6.2.4 South West bay experiment - ANGLED (45ᵒ)

For two weeks all blinds were kept horizontal (45º) in zone 1 (SE) and zone 2 (SW), this section showing zone 2. The ambient and radiant temperatures along with light intensity were recorded. The result of this experiment was compared with blinds open, close and horizontal for further analysis in the subsequent sections.

Figure 88: South & West Zone - Blinds 45°

Figure 89: South : All Blinds 45°

Figure 90: West : All Blinds 45°



The data collected over fourteen days was plotted as seen in the graph below. The outdoor temperature and the solar radiation showed large range of variations in outdoor conditions. Two sunny days were expanded for further analysis.

Graph 21: South West - All Blinds 45ᵒ

From the graph below, it is observed that the ambient and radiant temperatures follow each other very closely and there is no peak in the radiant temperatures even in the afternoon. This data is compared with blinds open, closed and horizontal in the subsequent section. However, from this data it can be said that blind slats at 45ᵒ angle seem to work in South West.

Graph 22: South West All Blinds 45 (Sunny Days)

It is observed however, that the daylight levels are always above the recommended standards of comfort, both IESNA as well as the observed 200 lux daylight level that occupants are comfort within.



6.2.5 Comparisons of experiments

Comparisons were made within the South West bays with different blinds slats angles. Following are the list of comparisons made, similar to the comparisons made for South East in earlier section. Each of these will be discussed in detail in this section. 1. South West – Blinds Open vs. Blinds Closed 2. South West – Blinds Open vs. Blinds Horizontal (0°) 3. South West – Blinds Open vs. Blinds 45° 4. South West – Blinds Closed vs. Blinds Horizontal 5. South West – Blinds Closed vs. Blinds 45° 6. South West – Blinds Horizontal vs. Blinds 45°

Two days with similar outdoor conditions from each of the combination were identified (out of at least seven days of each blinds position) and the data was compared and analyzed. A thermo graphic camera was used to compare the window surface temperatures due to different blind positions. As mentioned in the earlier section, unified glare ratio analysis was carried out for these set of experiments too. Recommendations in the subsequent chapter were made based on the data comparison from all the above mentioned methods. The highlighted comparisons could not be made since comparable days with similar outdoor conditions could not be found.



1. South West – Blinds Open vs. Blinds Closed

Graph 23: South West (Blinds Open vs. Blinds Closed) Outdoor Conditions Comparison ( Mild Sunny Day)

Graph 24: South West Blinds Open Vs. Blinds Closed Comparison

From the above graph, following points can be concluded:

1. Interior ambient temperatures without conditioning ranged from 68-74°F with daylight levels of 150-300 lux when blinds were closed.

2. Due to building shading, closing blinds on a day with temperatures rising from 50-65°F (8 am-6 pm) resulted in no significant ambient temperature differences, but a two hour 6°F reduction in radiant temperature conditions when the sun entered.



3. Opening blinds at night allowed 3°F of free cooling through radiation to the night sky. This observation supports the hypothesis that the blinds act as an insulation layer to the façade. This is a matter of further exploration.

2. South West – Blinds Open vs. Blinds Horizontal (0°) & 3. South East – Blinds Open vs. Blinds 45° experiments results not available.



4. South West – Blinds Closed vs. Blinds Horizontal

Graph 25: South West (Blinds Closed vs. Blinds Horizontal) Outdoor Conditions Comparison ( Hot Cloudy Day)

The graph below shows the comparison of data for blinds closed and blinds horizontal. Since the outdoor temperature with blinds horizontal was higher during at the beginning of the day as seen in the graph above, the difference between the indoor temperatures during that time of the day was very high as seen in the graph below and therefore not compared.

Graph 26: South West - Blinds Closed vs. Blinds Horizontal



Following conclusions can be drawn from the comparison: 1. No peak is seen in radiant temperatures with blinds closed as well as blinds horizontal. Therefore,

blinds can be kept horizontal so as to overcome the disadvantage of 100% view blockage with blinds closed.

2. Daylight levels with blinds horizontal were higher than the recommended standards unlike blinds closed. Blinds closed would therefore reduce the problem of glare but at the cost of 100% blockage of view.

3. The outdoor temperatures when blinds were horizontal dropped slightly as compared to blinds closed. The indoor temperatures with blinds horizontal dropped at least by 1°F as compared to blinds closed. This supports the hypothesis regarding blinds as insulation to the facade.

It is observed that interior blinds in closed position maintain cooler temperatures in the South West during afternoon than in horizontal position.

Figure 91: Thermographic image with Blinds Horizontal

Figure 92: Thermographic image with Blinds Closed

5. South West – Blinds Closed vs. Blinds 45° experiments results not available.



6. South West – Blinds Horizontal vs. Blinds 45°

Graph 27: South West (Blinds Horizontal vs. Blinds 45) Outdoor Conditions Comparison

( Hot Partly Sunny Day)

Graph 28: South West - Blinds Horizontal vs. Blinds 45 Comparison Given the external building shading, field studies reveal that setting south and west blinds to a better shading position at a 45o tilt will reduce air temperatures by 0.5-1oF as compared to blinds set horizontally. Daylight levels were sustained at 400-600 lux for effective task lighting. Similar to blinds closed, blinds 45 seem to keep the indoor temperatures higher as temperatures with blinds horizontal seem to drop at least 1F at night. This supports the hypothesis that blinds act as an insulation layer. May 6 being the weekend, indoor temperatures were uniformly raised by 1.89° F to reflect average contribution of week day internal gains.



6.2.6 Comparison of base cases between South East and South West

Comparisons were made within the South East and South West bays base cases i.e. blinds open, blinds closed, blinds horizontal and blinds 45ᵒ. Each of these will be discussed in detail in this section.

1. South East – South West base case (All Blinds Open) 2. South East – South West base case (All Blinds Closed) 3. South East – South West base case (All Blinds Horizontal, 0º) 4. South East – South West base case (All Blinds 45º)

1. South East – South West base case (All Blinds Open) Seven days data of South East (sensor 1) and South West (sensor 2)with blinds open were compared as seen in graph below to analyze the impact of orientation.

Graph 29: South East - South West (All Blinds Open) Comparison

From the above graph, it is observed as expected that due to the impact of orientations, South East shows peak in radiant temperatures in the morning and South West shows peak radiant temperatures in the afternoons on sunny days. It is also evident from the graph above that the afternoon temperature peaks in the south west are 10ºF higher than those during morning in south east. The light intensity due the direct solar incidence in both orientations is above the recommended levels which would cause visual discomfort.



2. South East – South West base case (All Blinds Closed) Seven days data of South East and South West with blinds closed were compared as seen in graph below to analyze the impact of orientation.

Graph 30: South East - South West (All Blinds Closed) Comparison

From the graph above it is observed that South West has slightly more (1ºF) indoor temperatures as compared to South East. However, there is no significant rise in temperatures in either of the bays throughout the day even on sunny days. South West recorded more light intensity whereas the light intensity on South East was close to the recommended standards at least for the last four days. [1]

3. South East – South West base case (All Blinds Horizontal) Seven days data of South East and South West with blinds horizontal were compared as seen in graph below to analyze the impact of orientation.

Graph 31: South East - South West (All Blinds Horizontal) Comparison

[1]



The graph above reveals that the temperatures in South West are always higher than South East. However, the temperature difference between ambient and radiant temperatures in South East is slightly higher than that in South west. As mentioned earlier, radiant temperature peaks are seen in South East with blinds horizontal but not in South West.

4. South East – South West base case (All Blinds 45ᵒ) Seven days data of South East and South West with blinds closed were compared as seen in graph below to analyze the impact of orientation.

Graph 32: South East – South West (All Blinds 45ᵒ) Comparison

From the graph above it is observed that South East and South West temperatures follow each other closely. However, there is a peak in the radiant temperature as well as light levels in the East in mornings whereas there is no peak in the afternoon in West, which could lead a conclusion that blind slats at 45ᵒ do not work efficiently in South East in the mornings. It also leads to a positive conclusion that keeping blind slats at 45ᵒ can help shave off the radiant peaks occurring in the West in the afternoons due to direct solar incidence.



6.2.7 Thermographic Images Analysis

The table below shows the actual spot measurements of surface temperature difference in °F with different blinds locations (internal and external) and blinds slats position for both South East and South West test bays as described separately in the earlier section. The spot measured is depicted with a white triangle.

Figure 93: Spot measurement : SW - sophisticated light

redirection blinds

Figure 94: Spot measurement : SW - concave up light

redirection blinds Difference of up to 1° F seen between the two types of blinds.

Figure 95: Spot measurement : SE - external blinds

closed

Figure 96: Figure 95: Spot measurement : SE - internal

blinds closed Difference of up to 2°F seen between internal & external blinds

83°F

82.1°F 84.8°F

84.1°F



Figure 97: Spot measurement : SW - external blinds

horizontal

Figure 98: Spot measurement : SW - internal blinds

horizontal Difference of up to 4°F seen between internal & external blinds

Figure 99: Spot measurement : SE - external blinds

horizontal

Figure 100: Spot measurement : SE - internal blinds

horizontal Difference of up to 6°F seen between internal & external blinds

Figure 101: Spot measurement : SE with external louver

Figure 102: Spot measurement : SE without external

louver Difference of up to 0.5°F seen with and without external louvers

81.1°F 85.4°F

81.9°F

79.7°F

80.5°F

87°F




From all the comparisons made in the earlier section for South West bays, following recommendations can be made based on the observations while keeping in mind the limitations of the field experiments.

1. Unlike in the mornings in South East, the peak radiant temperatures in South West during afternoons can be shaved to a large extent, if not completely prevented, by blinds horizontal and blinds 45. However, both horizontal as well as 45 slat positions result in higher day light levels and could cause glare issue. With the blinds closed both radiant temperature peak and high day light levels can be avoided but with a disadvantage of 100% blockage of view. This decision would therefore have to be taken with respect to the occupancy in the space. If there is occupancy then blinds can be kept horizontal to allow more access to outdoor, if not then blinds 45° would keep the space cooler. But no blinds open during afternoons in South West.

2. Blinds at 45° position work better than blinds horizontal by maintaining cooler indoor temperatures.

3. From the experiments it has been observed that blinds provide some amount of insulation in horizontal, closed and 45ᵒ slat angles position. Therefore during heating season, the blinds should remain closed at night to reduce heat loss. During cooling season, the blinds should remain open or horizontal during nights depending on the outdoor temperature to reduce heat gain.

With further exploration, if it is proved that the blinds indeed add an insulating layer to the façade, then it is recommended to close the blinds during the cold nights to minimize the heat loss and keep them completely open during warm nights to precool the space. However, this recommendation is not valid during summers when the night temperatures are very high.



6.3 West bay Experiments

The figure below highlights (in yellow) the exact location of the West test bays in IW.

Figure 103: West test bays Highlighted



6.3.1 West bay experiment – OPEN, CLOSE, HORIZONTAL (0°), 45°

Since it was difficult to find comparable days with similar outdoor conditions in earlier experiments conducted in South test bays, in the West, side by side experiments were conducted with two test bays. It was important to calibrate the two bays for them to be comparable. Similar to the experiments in the South, experiments with same blinds positions in both bays were performed and the data was compared. The furnishing, occupancy and equipment were kept identical in both the bays at all times. It was observed that the bay adjacent to the large conference space was almost always, with any blinds position, at least 2°F cooler than the other bay which was adjacent to the next workspace. As mentioned earlier in the limitations section, the heat dispersion due to open plan office and low height partitions resulted in this difference between the two adjacent bays.

Graph 33: West Bays : All Blinds Open

Graph 34: West Bays : All Blinds Closed



Graph 35: West : All Blinds Horizontal

The graphs above show the difference between the two adjacent test bays. Therefore, the data gathered from the side by side experiments was analyzed with two different approaches as described in the following section.

Six different experiments were conducted as listed below with blinds open and blinds closed as controls. The experiments are as follows:

1. Blinds Closed (Control Bay) VS Blinds Open (Test Bay) 2. Blinds Closed (Control Bay) VS Blinds 45° (Test Bay) 3. Blinds Closed (Control Bay) VS Blinds Closed (Test Bay) – Base Case 4. Blinds Open (Control Bay) VS Blinds Closed (Test Bay) 5. Blinds Open (Control Bay) VS Blinds 45° (Test Bay) 6. Blinds Open (Control Bay) VS Blinds Open (Test Bay) – Base Case



6.3.2 Side By Side Experiments Comparison

The side by side experiments were conducted in the two adjacent office spaces in the West keeping one as the control bay (blinds closed) and other as the test bay (blinds open). As mentioned earlier, similar blinds positions were tested within both the bays for a period of two days for each setup. It was found that one of the bays was always warmer than the other due to the location and adjacency conditions. Due to this, the data gathered from these experiments was analyzed with two different approaches. The first approach was deducting the difference found between the two spaces in the base case (both bays with all blinds closed), from the entire data of the other set of experiments. To validate this approach, the outdoor conditions for all the days were compared with each other and only the comparable days were used for further analysis. The resultant graphs as seen below show the increase in indoor temperature or heat gain due to change in the blinds positions from closed to open or 45°. It must be noted that the peak in radiant temperatures seen during the morning in the graphs in both approaches is due to the presence of skylight in the existing structure where the field experiments were carried out.

It is observed from the graphs comparing ambient temperatures, that having blinds open result in maximum heat gain thus maintaining the indoor ambient temperatures at least 2°F higher as compared to blinds closed (base case) and at least 1°F higher than blinds 45°. It may therefore be said that blinds closed would keep the indoor temperatures lower throughout the day in summer and help in reducing cooling load. However, the major drawback of this setup is the 100% blockage of access to view. This is highly undesirable as many studies have shown a strong correlation between the increase in individual productivity due to access to nature. Therefore, it would be desirable to keep the blinds slats at 45° so as to keep the indoor temperatures cooler and provide some percentage of outdoor view to the occupants. Ideally, by integrating occupancy sensors and blinds controls, maximum advantage of these findings can be achieved by keeping the blinds closed when the room is occupied and changing the blinds slats position to 45° when the room is occupied during a hot sunny or partly sunny day in this orientation.



Graph 36: West - Blinds Closed vs. Blinds Open (Ambient temperatures) Comparison

(With Data Adjustment)

Graph 37: West - Blinds Closed vs. Blinds 45° (Ambient temperatures) Comparison


Graph 38: West - All Blinds Closed (Ambient temperatures) Comparison (With Data Adjustment)



It is observed from the graphs comparing radiant temperatures, that blind open result in at least 3°F higher radiant temperatures than blinds closed and at least 2°F higher than blinds 45°. As mentioned earlier, although blinds closed would be the ideal solution to prevent radiant surface asymmetry, blinds 45° would help shave off some amount of radiant temperature asymmetry while providing some percentage of outdoor view. It is also observed that blinds 45° do not prevent the peak in radiant temperatures in the afternoon and that would result in visual and thermal discomfort to the occupants. Therefore, if occupancy sensors are integrated with the blinds controls, the blinds should be kept closed if the room is occupied during the afternoon when there is a maximum potential for peak in radiant temperatures and then changed to blinds 45° to permit view.



Graph 39: Graph 36: West - Blinds Closed vs. Blinds Open (Radiant temperatures) Comparison


Graph 40: Graph 37: West - Blinds Closed vs. Blinds 45° (Radiant temperatures) Comparison


Graph 41: West - All Blinds Closed (Radiant temperatures) Comparison (With Data Adjustment)



The second approach to analyze the data was to analyze the data without any adjustments. In this approach, the comparison was made individually for each setup and the temperatures in the test bay were plotted against the average temperatures between both the bays. The resultant graphs as seen below show that blinds closed kept the indoor ambient and radiant temperatures closer to the comfort level than blinds 45° and blinds open.

Graph 42: West - All Blinds Closed (Ambient temperatures) Comparison (Without Data Adjustment)

Graph 43: West - All Blinds 45° (Ambient temperatures) Comparison (Without Data Adjustment)

Graph 44: West - All Blinds Open (Ambient temperatures) Comparison (Without Data Adjustment)



Graph 45: West - All Blinds Closed (Radiant temperatures) Comparison (Without Data Adjustment)

Graph 46: West - All Blinds 45° (Radiant temperatures) Comparison (Without Data Adjustment)

Graph 47: West - All Blinds 45° (Radiant temperatures) Comparison (Without Data Adjustment)



6.3.3 Radiant Surface Temperature Analysis

The table below shows the actual spot measurements of surface temperature difference in °F with different blinds locations and slats position for West test bays in morning and afternoon.

Table 11: Thermographic Images for West

Blinds Closed during morning External louvers [1] : 75.6° F Internal louvers [2] : 77.4° F

Blinds Open during morning Spot Measurement : 78.4° F

Blinds Closed during afternoon External louvers [1] : 82.3° F Internal louvers [2] : 87.4° F

Blinds Open during afternoon Spot Measurement : 88.6° F

1 2

1 2




From all the comparisons made in the earlier section for West bays, the following recommendations can be made for hot and sunny or partly sunny day based on the observations while keeping in mind the limitations of the field experiments.

1. Blinds should remain at 45° during hot and sunny or partly sunny days except for a couple of hours in the afternoon if the room is occupied. Blinds should remain closed during those couple of hours in the afternoon to prevent peak in the radiant temperature and also avoid glare.

2. If the room is not occupied, the blinds should remain closed at any time of the day to reduce the

heat gain thus reducing the cooling loads.



6.3.5 Controls Decision Flow Chart

Based on the observations from the field tests regarding indoor ambient and radiant temperatures along with day light intensity, a controls decision flow chart was developed. Occupancy has been considered in the decisions in this flow chart assuming that occupancy sensors would be installed which was not a part of the field experiment.

Figure 104: Controls decision flow chart for West

As mentioned earlier in the South East experiments section, the items on the left hand side that include solar radiation, luminance levels, outdoor and indoor temperatures are the decision variables to address the seasonal variables. There are different controls logics for morning, afternoon and night to address the daily dynamics. As per the chart seen below, in case of sunny hot mornings, the blinds can be kept at



45° to maintain the outdoor view if the room is occupied but maintained closed if there is no occupancy so as to reduce the cooling load. In case of cold sunny days, the blinds should be maintained horizontal or open to take full advantage of free solar heat gain. Since the orientation is West, there is not much issue of glare during the morning. In case of hot sunny afternoons, blinds must be kept closed to provide occupant comfort and reduce cooling load. The remaining chart should be read with the same logic.

There are certain set of equipment that would be needed to use the controls logic as shown here and in the earlier section. In case of automated control, there would be a need for outdoor temperature sensor and solar tracking device installed outside the building and an electronic actuator installed inside the building to open and close the blinds automatically. In addition to this, occupancy sensor integrated with the above mentioned sensors would help realize the complete energy saving potential of this strategy. For manual control, along with the above mentioned sensors, the C3 dashboard, developed by ( CMU Center For Building Performance & Diagnostics) can be installed that prompts the user to open or close the blinds depending on the outdoor and indoor conditions.



7 Simulation To quantify the findings from the above experiments for summer, a simulation exercise was carried out in Energy Plus software. In attempt to generalize the findings, a prototype small office building (5000 sq ft) in climate zone 5A developed by Pacific Northwest National Laboratory (PNNL) was used for the simulation. PNNL has developed these prototype models based on Department of Energy’s (DOE) reference models following ASHRAE 90.1.2010. However, it must be noted, that these prototypes are designed to be almost 30% more efficient than ASHRAE 90.1.2010 by having more high performance envelop assemblies thus reducing the energy loads at the onset and therefore cannot be used as base cases. Since the field experiments were conducted only in South and West orientation, the modifications were applicable only zone wise. This was the primary reason to choose a small scale office building since it has unitary HVAC systems for each zone and therefore the results can be generated per zone, unlike in case of medium or large scale offices having multi-zone VAV systems.

According to CBECS 2003, the vast majority of the commercial buildings fall under the smallest size category, that is, 5000 sq ft or less (US Energy Information Administration, 2009).

Figure 105 : Number of Buildings and Floor space by Size of Building. (US Energy Information Administration, 2009)

However, as per the Energy Information Administration’s Annual Energy Outlook report 2011, by 2035, commercial building floor space is expected to reach 109.8 billion sq ft which means a 53% increase over 2003 levels. (Center for Sustainable Systems, University of Michigan, 2011). Therefore, the findings from this simulation study cannot be generalized; however, it can be considered as a conservative indication for energy savings for office buildings up to 20 stories in this particular climate zone.



PNNL prototype model for climate zone 5A is located in Chicago and hence for the present study, the location was changed to Pittsburgh along with its weather file downloaded from DOE’s official website. The model with these specific changes was then simulated and considered as base case for the purpose of this study alone. The set point temperatures were then altered, specific to the zones, based on the findings from the field experiments and each case was simulated individually to achieve the energy consumption and energy loads changes with each blinds setting. Thus the decreased cooling loads were converted into energy consumption and the reductions seen from the simulations were used as benefits in the triple bottom line calculation to predict return of investments in this strategy in the subsequent section. It must also be noted that the simulations were done only for cooling load reductions since a lot of factors affect the heating loads which would need more detailed inputs in the simulation.

The prototype model used for simulation had following building description and specifications (Pacific Northwest National Laboratory, Department of Energy, 2007):

Perimeter zone depth: 16.4 ft.

Four perimeter zones, one core zone and an attic zone.

Percentages of floor area: Perimeter 70%, Core 30%

Number of Floors 1

Window Fraction(Window-to-Wall Ratio)

5500(90.8 ft x 60.5ft)

Building shape

1.5

Total Floor Area (sq feet)

Thermal Zoning

Floor to floor height (feet)

10

Azimuth non-directional

24.4% for South and 19.8% for the other three orientations (Window Dimensions:

6.0 ft x 5.0 ft punch windows for all façades)

Shading Geometry noneWindow Locations evenly distributed along four façades

Aspect Ratio

Floor to ceiling height (feet)10

Glazing sill height (feet) 3(top of the window is 8 ft high with 5 ft high glass)

2003 CBECS Data and PNNL's CBECS Study 2007.



Following simulations were carried out for specific periods:

South: 1. Blinds Open VS Blinds Closed: April 10th – April 13th 2. Blinds Horizontal VS Blinds 45°: May 1st – May 31st

West: Blinds Open VS Blinds Closed: May to August The weather file used for the purpose of this simulation was sourced from DOE weather data, which is the data that is representative of last 50 years of typical trend seen in the region. Typically, being a heating dominant region, Pittsburgh experiences cold days even during the swing season and therefore most of the days in April and May in the weather file showed heating loads. However, the year in which the field experiments were conducted, had unusually hot days during the swing season. Therefore, to conduct the simulations for the experiments done during the swing season, specific days had to be identified from the weather file that represented the cooling days, which were very less in number. Therefore, the simulations carried out for the South bay experiments were done using very short run periods. The experiments conducted in summer season were simulated for the entire cooling season period from May to August. Therefore, the simulation results from the West bay are used in further cost benefit analysis. The simulations calculated the site and source energy along with cooling and heating loads for each zone with the changed set point schedules. Listed below are the percentage energy savings as compared to the base case.

South Zone:

1. Blinds Open VS Blinds Closed: 12.46 % 2. Blinds Horizontal VS Blinds 45°: 3.94%

West Zone:

Blinds Open VS Blinds Closed: May to August: 2.24%

It must be noted that these energy savings reflect only the cooling energy savings and does not include lighting loads. The health and productivity benefits would be an addition to these savings. Therefore, these savings can be considered conservative.



8 Benefits

There are many benefits of using the solar shading devices as a passive strategy in highly glazed office buildings. Energy savings due to reduction in heating, cooling as well as lighting loads form a major part of the economic benefit for the owner or operations management. Besides the energy savings, there are many parallel benefits of this strategy. For example, when the energy loads are reduced, the mechanical equipment sizing can be reduced which in turn would help reduce the number and size of mechanical rooms and shafts, thus increasing the usable space within the building. Additional benefits of using solar shading devices, especially venetian blinds, include improving indoor daylight levels, reducing glare and providing access to natural environmental to the occupants. Many studies such as (Thayer B., Romm J., Browning W., 1995) have shown a strong link between improvement in occupant health and productivity due to access to nature and glare reduction.

8.1 Energy, Health and Productivity Benefits

The Commercial Buildings Energy Consumption Survey reveals that there are twice as many workers in office buildings as any other building type. Such staggering numbers of people spend at least 8 hours per day inside the office buildings and therefore it is important to have a comfortable environment in these buildings to reduce absenteeism and increase the productivity.

Figure 106: Number of occupants per building sector (US Energy Information Administration, 2009)



Along with energy savings, numerous studies have confirmed the importance of daylight, thermal comfort and access to view in commercial buildings for improving occupant health, visual comfort and individual productivity. In 1998, Lee et al estimated a simple payback of about 10 years considering only lighting and cooling energy savings for their 34 sq. m test bed for field experiment in Oakland, California. In 1992, Osterhaus and Bailey identified 3% increase in productivity in visual tasks by reducing glare discomfort.

By taking the energy savings result for the West zone from the simulation and the productivity benefits from the literature review as mentioned above, triple bottom line calculations were made to prove the large scale impact of the investment in this strategy, beyond mere energy savings. The calculations were made based on the square footage and energy savings from the simulation model and certain assumptions as mentioned below.

Assumptions:

1. Total office area : 5500 sft 2. West zone area : 724 sft 3. Window glass area : 120 sft 4. Number of occupants : 4 (assuming 200 sft per occupant) (CMU CBPD BIDS Database) 5. Average annual electricity cost for USA : 12.9c per kWh (USA Department of Labor) 6. Cost of conventional blinds: $2.50 to $3.50 & cost of Nysan specialty blinds $12 to $20 as informed

by Richard Wilson from Nysan. 7. Energy savings : 2.24% taken from Energy Plus model 8. Productivity increase : 3% (Osterhaus W., Bailey I., 1992) 9. Additional assumptions related to air pollution, emissions, water pollution, etc are given in the

appendix.

It must be noted that the increase in productivity was related only to the visual tasks such as data entry, design & engineering, emails, writing and researching. Therefore the time spent on these tasks was assumed as 35% of the total time spent in the office and used in calculations as seen in the table below. (CMU CBPD BIDS Database)



Table 12: Triple Bottom Line Calculations



8.2 Industry Recognition: Achieving LEED NC Version 3 Credits As seen from the research articles, LEED accreditation is being pursued rapidly by many clients as well as professionals. This could be an incentive to convince the client to invest in the higher first cost required for the application of some of the products for this strategy. The credits that can be targeted by using or as a result of using these strategies are listed below (LEED 2009 NC & Major Renovations):

1. Energy & Atmosphere (EA) Credit 1: Optimize Energy Performance (1–19 Points) Intent: To achieve increasing levels of energy performance beyond the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use. In addition to the high efficiency mechanical system, use of internal & external solar shading devices reduce heating, cooling and lighting load thus further reducing the overall energy consumption, this credit would be easy to achieve.

2. Indoor Environmental Quality (IEQ) Credit 7.1: Thermal Comfort—Design (1 Point) Intent: To provide a comfortable thermal environment that promotes occupant productivity and well-being. Potential Technologies & Strategies: Design the building envelope and systems with the capability to meet the comfort criteria under expected environmental and use conditions. Evaluate air temperature, radiant temperature, air speed and relative humidity in an integrated fashion, and coordinate these criteria with IEQ Prerequisite 1: Minimum IAQ Performance, IEQ Credit 1: Outdoor Air Delivery Monitoring, and IEQ Credit 2: Increased Ventilation.

3. Indoor Environmental Quality (IEQ) Credit 8.1 & 8.2: Daylight and Views (1 Point Each) Intent: To provide building occupants with a connection between indoor spaces and the outdoors through the introduction of daylight and views into the regularly occupied areas of the building. Potential Technologies & Strategies: Design the building to maximize interior day lighting. Strategies to consider include building orientation, shallow floor plates, increased building perimeter, exterior and interior permanent shading devices, high-performance glazing, and high-ceiling reflectance values; additionally, automatic photocell-based controls can help to reduce energy use. 4. Innovation in Design (ID) Credit 1 – (1-5 Points) – Possibility can be explored Substantially exceed a LEED 2009 for New Construction and Major Renovations performance credit such as energy performance or water efficiency. Apply strategies or measures that demonstrate a comprehensive approach and quantifiable environment and/or health benefits



9 Recommendations

This study focused on identifying the best blinds positions strategy for South East, South West and West orientations which would help reduce the energy consumption and improve indoor environmental quality. One of the main observations during the experiments was that there is a considerable amount of radiant temperature asymmetry which can result in peak energy loads causing occupant discomfort. Based on the observations from the field experiments and taking into consideration the glare and indoor temperatures, certain recommendations were made for different orientation, with an understanding that there is sometimes a tradeoff between energy savings and occupant comfort. The tables below show a summary of results from all the experiments.

Table 13: South East - Experiments result summary

Table 14: South West - Experiments result summary

Few of the important recommendations are highlighted here, detailed recommendations can be found in the earlier sections:

1. On sunny or partly sunny hot day, blinds must remain closed in the morning in the South East orientation to prevent glare and reduce the heat gain. No other blinds slats positions (horizontal - 0°, open or 45°) are recommended. However, since the view to outdoor would be compromised by keeping blinds closed, the blinds positions should be changed after the sun moves away from the window plane. Blinds at 45° work well in South West and West orientation during the afternoons to shave off the peak in radiant temperatures and having less heat gain, and therefore, if the room is occupied the blinds do not have to be completely closed blocking the outdoor view.

SOUTH EAST OPERATIVE TEMPS RADIANT PEAK SHAVING NIGHT TIME FREE COOLING

BLINDS OPEN VS. BLINDS CLOSED 2° F (closed) 8° F (closed) 3° F (open)

BLINDS HORIZONTAL VS BLINDS 45° 1 - 2° F (45°) 6° F (45°) 1° F (horizontal)

BLINDS CLOSED VS BLINDS HORIZONTAL NA NA 2° F (horizontal)

SOUTH WESTOPERATIVE TEMPS RADIANT PEAK SHAVING NIGHT TIME FREE COOLING

BLINDS OPEN VS. BLINDS CLOSED NA 8° F 3° F

BLINDS HORIZONTAL VS BLINDS 45° 0.5 - 1° F NA 1° F

BLINDS CLOSED VS BLINDS HORIZONTAL NA NA 1° F



2. It was observed in the field experiments that blinds act as an insulation layer to the façade and this observation should be considered while developing the controls algorithms.

3. The full potential of dynamic blinds with controls algorithms in terms of maximum energy savings and occupant comfort can be realized if the system is integrated with occupant sensors.

Along with the field experiments and other research, it is important to discuss what is realistically achievable today with the available resources and possible developments in near future. During the discussion about the current professional scenario, Barbara Smith, a representative of Nysan, Hunter Douglas mentioned that since there are so many industries involved in any given building project, a wide adoption of such integrated systems proves to be very expensive and extremely difficult. She also mentioned that like her, many other manufacturers are interested in exploring the possibilities but there is a lack of expertise and a collective approach towards this goal. Simulation software today proves to be one of the solutions for this problem due to its interoperability. Another solution is to have design charrettes where the manufacturers work with the designers and sustainability experts to develop or advance the existing products and controls.

It has been learned from the literature review and discussions with sales representatives that it is a vicious cycle of demand and supply, lack of knowledge along with issues of privacy of information that act as barriers for wide spread acceptance and application of these products. There is still skepticism amongst the clients about the possibly long return of investment period for these products due the high first cost. As discussed by many authors in several studies mentioned in earlier chapters, information on approximate energy savings achievable by all the commercially available products could prove to be extremely useful. This would not only help the designers and clients make informed decisions about the cost benefits of these products, but with the increase in demand, these products could be manufactured and installed at much cheaper rates. The dialogue among the clients and manufacturers of these products should therefore continue beyond the installation phase till post occupancy and the energy savings data should be maintained for future references.



10 Conclusion

The objective of this study was to explore the impact of blinds intervention on the operative temperatures and the indoor environmental quality during swing and summer season for highly glazed office buildings in US climate zone 5A. This research contributed to the area of sustainable design by quantifying the energy savings achievable by the use of solar shading devices, interior and exterior blinds in particular, and altering the blinds positions as per seasonal and daily variations on different orientations. Similar experiments supported by whole building simulation studies can be conducted to draw conclusions for different climate zones and building types. This would not only encourage wide application of such passive solar strategies in architecture in cost effective ways along with quantified results and recommendations but also encourage the development of sophisticated controls algorithms. As mentioned in the methodology section, new simulation software are being developed and upgraded to predict the solar heat gain of complex fenestration systems. This research and its results could be coupled with the upgraded simulation software for more informed study and application.

11 Future Scope of Work

Based on the study undertaken in this report, listed below are steps that should be taken in future research:

1. Comparisons that were not made in this report such as blinds open vs blinds 45° and so on. 2. Conducing controlled field experiment. 3. Installing one type of blinds in one location (internal or external) at a time understand the impact of

the specific intervention. 4. Energy simulations to be carried out for the existing building using real time weather data. 5. Studies correlating occupant comfort and productivity to the blinds intervention to be conducted. 6. Triple bottom-line calculations with annual benefits for the entire building. 7. Development of smart controls algorithm for all orientations (East, West and South) for all seasons

with in depth consideration of daily dynamics.

The literature review revealed a few other topics that need to be undertaken in future research. In their 2003 study, Selkowitz et al mention that hierarchy of control priority is a matter of further exploration. They mention that if occupant controls are provided without perfect systems integration, the solution can turn out to be highly inefficient and extremely expensive. (Selkowitz S., Aschehoug O., Lee E., 2003) This observation was put forth earlier by Lee et al in their 1998 study. (Lee E., Selkowitz S., DiBartolomeo D., 1998)



In their 2012 meta-analysis study, Olbina et al discuss the need for in depth research on development of automated split controlled blinds. (Olbina S., 2012)

Figure 107 : Function of three sections of split control blinds , Olbina S. 2012

Figure 108 : Split and conventional automated control systems for blinds, Olbina S. 2012

Lee et al mention with regards to their findings from field tests along with simulations that automated interior venetian blinds can be more effective than automated roller shades, however, a lot of initiative from the manufacturers will be needed to modify the existing products to improve the motorized performance and also make it more cost effective. (Lee E., DiBartolomeo D., Selkowitz S., 1998)



12 Bibliography

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27. Los Alamos National Laboratory. (n.d.). Sustainable Design Guide. Retrieved from http://apps1.eere.energy.gov/buildings/publications/pdfs/commercial_initiative/sustainable_guide_ch4.pdf

28. Olbina S., H. J. (2012). Daylighting and thermal performance of automated split controlled blinds. Building and Environment.

29. Osterhaus W., Bailey I. (1992). Large area glare sources and their effect on discomfort and visual performance at computer stations.

30. Pacific Northwest National Laboratory, Department of Energy. (2007). Prototype Building Models. Retrieved from http://www.energycodes.gov/commercial/901models/

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32. Park J. et al. (2012). Office Buildings Environment Design Report.

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39. Thayer B., Romm J., Browning W. (1995). Daylighting and Productivity at Lockheed Solar Today.

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43. Appendix Buildings Investment Decision Support: http://cbpd.arc.cmu.edu/bids/



Table 15: Baseline data assumptions for cost benefit calculations (CMU CBPD BIDS Database)

Baseline data assumptions for cost benefit calculationBaseline Item ValueGross Building area 724 SFGross Building square feet per employee 200 SFNumber of employees 4Annual Work Days 256Annual salary $45,000 per employeecooling energy use 5.5 kWh/SF

Energy cost per employee, annualConsumption per square foot 28.4 kWhEnergy cost $0.13 /kWhCost for Lower ambient and task $1.57 /SFCost for Ergolight ($3.20- $2.38 for downlighting w no specialized control $0.82 /SFCost for Daylight harvesting $0.95 /SFCost for Vacancy Sensors $0.75 /SFCost for blinds installation $3.52 /SFCost of efficient fixtures w automation $3.15 /SF

US Power Plant Emissions and Dollar Impacts

PollutantEastern Region (lb of pollutant per kWh of electricity) *

Ton of pollutant per kWh of electricity

Emission Impact Value**

CO2 1.6400 0.00082 $15.00CH4 0.0036 0.000001795N2O 0.0000 0.000000015NOx 0.0030 0.0000015 $7,450.00SOx 0.0086 0.000004285 $5,200.00PM10 0.0001 0.000000045 $4,850.00

0.000825830 $17,515.00US Power Plant Water Consumption (due to evaporation) and Cost of Water

2 gal (7.6 L) per kWh of evaporated water (National Weighted Average)0.002 cents per gallon

Annual Health Insurance cost $5,000 per employeeAnnual Health Cost related with Headaches $73 per employeeAnnual Headache related productivity loss 2.50 daysEye irritation $19 per employee

Absenteeism 1.70%



Table 16 : Triple bottom line calculations (CMU CBPD BIDS Database)

First cost increase per sf: $0.36Baseline first cost increase per sf: $261 ($0.36/sf x 724sf)First cost increase per employee: $65 ($261/4 employees)Annual energy Savings per employee $3.16 (5.5 kWh/sf x2.24% savings x $0.10 x 200) Annual O&M Savings per employee $0.00Total annual savings per employee $3.16Baseline annual savings: $13 ($3.16 x 4)NPV of the savings: $96 ($3.16 x 4 x 7.606)EVA ® ($164) (NPV of the savings - First cost increase)ROI: 4.85% (Savings per employee / FCI per employee)

First cost increase per sf: $0.36Baseline first cost increase per sf: $261 ($0.36/sf x 724sf)First cost increase per employee: $65 ($261/4 employees)Annual energy Savings per employee 25 (5.5 kWh/sf x2.24% savings x 200) Dollar Impact of CO 2 emission $0.30Dollar Impact of SO x emission $0.55Dollar Impact of NO x emission $0.27Dollar Impact of PM 10 emission $0.01Dollar Impact of water consumption $0.10Total Savings (eco+env) $4.39Baseline annual savings: $18 ($4.39 x 4)NPV of the savings: $133 ($4.39x 4x 7.606)EVA ® ($127) (NPV of the savings - First cost increase)ROI: 7% (Savings per employee / FCI per employee)

First cost increase per sf: $0.36Baseline first cost increase per sf: $261 ($0.36/sf x 724sf)First cost increase per employee: $65 ($261/4 employees)Annual productivity savings per emplo $473 ($45,000 x 3.00% prod. Increase x 35%)Annual health savings per employee 0 ($73 x 19%)Absenteeism $0.00 ($45,000*15%*1.7%)Total annual savings per employee: $477Baseline annual savings: $1,907.54 ($477 x 4 employees)NPV of the savings: $14,509 ($14,509 x 4x 7.606)EVA ® $14,248 (NPV of the savings - First cost increase)ROI: 732% (Savings per employee / FCI per employee)

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