USING SIMULATION TOOLS FOR ENHANCING RESIDENTIAL BUILDINGS ENERGY CODE IN EGYPT

Ahmed Nabih Ahmed 1, Mina Michel Samaan 2, Osama M.A. Farag 3 and Alaa S. El Aishy 4

1 Assistant Lecturer, Department of Architectural Engineering, University of Mansoura 2 Instructor, Department of Architectural Engineering, University of Mansoura 3 Professor, Department of Architectural Engineering, University of Mansoura 4 Lecturer, Department of Architectural Engineering, University of Mansoura

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ABSTRACT The Egyptian Residential Buildings Energy Code ERBEC was developed in 2006 to prescribe the minimum requirements for achieving thermal comfort and energy efficiency. A background of ERBEC is described, A single-family house is used as a case study, then an assessment of the impact of building’s envelope variants on heating and cooling loads is conducted. Sensitivity analysis is used to analyze the results of the simulation in order to identify the major elements that could play a significant role in enhancing the comfortable conditions and energy efficiency in residential buildings. Finally, the key factors affecting enhancing ERBEC are defined through a proposed roadmap.

INTRODUCTION Global Energy Problem: The rapid growth of energy use, worldwide, has raised concerns over problems of energy supply, energy sustainability and exhaustion of energy resources (Iwaro J., Mwasha A., 2010), this increasing consumption of energy sources has lead to serious environmental problems such as global warming, air pollution and acid rain (Janda, K. B., & J. F. Busch, 1994). Energy Standards In Developing Countries: Energy standard is one of the most frequently used instruments for energy efficiency improvements and can play an important role in enhancing energy efficient design in buildings (OECD, 2003). As seen in figure 1, there are two types of building energy standards: prescriptive standards that set separate performance levels for major envelope and equipment components, such as minimum thermal resistance of walls, are used more frequently, possibly due to their easier enforcement. On the other hand, overall performance-based standards, prescribing only an annual energy consumption level or energy cost budget, usually provide more incentives for innovation (Gann D. M. et al 1998). While the number of new buildings is growing rapidly in developing countries, energy prices and market do not encourage the use of energy efficient technologies (Hui, S. C., 2000), in addition to that

building energy standards are often ineffective or much less effective than predicted (UNEP, 2009). This is supported by the argument that while building energy efficiency standards exist in a number of developing countries, they are often only on paper due to insufficient implementation and enforcement (Deringer, J. et al, 2004).

Figure 1 Energy standard paths

Energy Standards In Egypt: The energy standard for housing in Egypt became law in 2005. The standard has both prescriptive and performance-based compliance paths. It also include minimum performance levels for air-conditioners and other appliances application (RIC, 2009). The code follows the ANSI/ASHRAE standard 90.2 Energy- Efficient Design of Low-Rise Residential Buildings in many aspects: structure, organization, purpose and compliance paths. However, the code is not specific to low-rise buildings as it covers all housing types and it adds requirements for electrical lighting and equipments as shown in figure 2. As stated before, ERBEC is far from being integrated into the construction industry in Egypt due to two main reasons:

1- The lack of awareness of the topic of energy efficiency amongst common construction practitioners in Egypt,

2- The absence of legislative support and enforcement,

Residential and commercial buildings energy consumption has been increasing to record more than 44% of total energy consumption in Egypt, due in part, to Egypt’s rapid increase in population (HBRC, 2006). Housing units of different types have been constructed throughout Egypt to meet this rapidly increasing demand for housing.

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In Cairo for instance, this urbanization has expanded into the desert prompting an upgrading of the residential building code in an effort to reduce energy consumption and improve thermal comfort in buildings.

Figure 2 The aspects that have been integrated in the

structure of ERBEC Source: Hegger M. et al 2008

Simulation Tools And Energy Standards: Building energy simulation is playing an increasingly important role in building design as relevant literature shows growing application of building thermal and energy simulation tools to building design problems in many parts of the world (CIBSE 1998, Clarke J. A. 2001, Hui S. C. M. 1998, Wong N. H. et al 2000, Waltz J. P. 2000). Consequently, the use of energy simulation software has increased significantly in the past ten years as consumers, engineers, and architects become more interested in applying energy conservation and efficiency techniques (Ahmad M. Culp C.H., 2006). With the advances in energy simulation programs numerous research studies have been looking at ways to better predict building energy performance using computer-generated models (Crawley D.B. et al, 2008, Choudhary R. et al, 2008, Wang N. et al, 2009). Therefore, using building energy simulation and modelling techniques is considered an important trend for modern building energy codes development which can help to understand the complex issues of building energy performance (Hui S. C. M. 2003). Based on these facts, this paper investigates the use of building energy simulation software in order to enhance and upgrade ERBEC through a comprehensive roadmap as shown in figure 3.

Figure 3 Suggested roadmap for enhancing ERBEC

METHODOLOGY Computational model of the case study building: Ecotect is used as it allows modelling, performing thermal and lighting analysis simultaneously while benefiting from user-friendly interface. Case-study characteristics: As shown in figure 4, two different models are created for a single-family house with the same floor area 96 m2:

The compact model is used to investigate the concept of compactness as a mean towards reducing the total surface area of the building in order to reduce heat gain and loss.

The second model is L-shaped model with the same floor area of the compact model. The aim of using this form is to explore the effects of building form on the energy performance of the building in addition to investigate the possibility of creating form/performance path for typical residential prototypes

Figure 4 Floor plans of case study models

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Sensitivity Analysis: Sensitivity analysis method is used to study the impacts of input parameters on different simulation outputs, as compared to a base case situation. Then, the results are interpreted so as to predict the likely responses of the system (Lam J.C. and Hui S.C.M. 1996) Important input design parameters of the building systems are identified and analysed from the points of view of heating and cooling loads of the HVAC system. The purposes of the analysis are:

1- To assess the significance and impact of input design parameters,

2- To identify important characteristics of the input and output variables,

3- To study the responses of building systems to perturbations,

SIMULATION PROCEDURES Energy Simulation In order to identify the most important parameter in envelope design, Sensitivity Analysis method is used to test the building envelope’s U value variants against total heating and cooling demand as shown in figure 5:

Using traditional buildings materials, which are commonly used in Egyptian residential construction sector as a base case,

Adding insulation to the building’s exterior walls configuration using three different EPS thicknesses as prescribed by ERBEC,

In this stage the same insulation variants were tested in the roof configuration of the building,

Since ERBEC defines fenestration parameters through Solar Heat Gain Coefficient SHGC and Shaded Glass Ratio SGR values, three different alternatives were used regarding envelope fenestrations: shading the single glass windows, using double glass and finally using double glass with low emissivity.

In ERBEC, exterior walls’ U values are indicated by orientation, so this stage tests upgrading walls insulation in each direction separately.

Finally, electric lighting analysis was used in all building’s spaces, and solar collector is used to generate electricity as a renewable energy source that could supply the buildings electrical lighting energy demand.

Lighting Simulation A model with code-compliant fenestration requirements – which basically, are shading devices specifications - is compared to the base case in order to evaluate the parameters indicated by the code in the field of day-lighting and window shading design parameters.

Figure 5 Stages of energy simulation

ANALYSIS Energy Simulation: 1- Wall Insulation Figure 6 illustrates the total heating and cooling loads per square meter of three alternative wall insulations compared to the base case.

Adding 2cm EPS insulation to the exterior brick walls has reduced loads by 11% in both of the compact and L-shape model.

Using 6cm EPS and 8cm EPS has recorded close results as they reduced loads by 15% and 16% respectively in both models.

65

75

85

95

105

115

125

135

U= 1.6 U= 0.8 U= 0.4 U= 0.3

KW

h/m

2

Compact L-shape

Figure 6 Total heating and cooling loads for wall insulation alternatives

2- Roof Insulation: Figure 7 illustrates the total heating and cooling loads per square meter of three alternative roof insulations compared to the base case.

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Adding 2cm EPS to the roof has reduced total loads by 33% in compact model and 23% in L-shape model. While increasing EPS thickness to 6 and 8 cm has reduced loads by 41% and 43% respectively in compact model, 31% and 33% in L-shape model respectively.

65

75

85

95

105

115

125

135

U= 1.6 U= 0.8 U= 0.4 U= 0.3

KW

h/m

2

Compact L-shape

Figure 7 Total heating and cooling loads for roof insulation alternatives

3- Windows Upgrade: Figure 8 illustrates the total heating and cooling loads per square meter of using shading devices and two alternative window glass types compared to the base case.

Installing shading devices has reduced heating and cooling loads in both models by 1%.

Using double glass then low E. glass caused a reduction in total loads by 5% and 8% respectively in the compact model, while it has reduced total loads by 9% and 12% respectively in the L-shape model.

105

110

115

120

125

130

Single Shading D. G. Low-E

KW

h/m

2

Compact L-shape

Figure 8 Total heating and cooling loads for window alternatives

4- Wall Insulation Variants: In order to assess the code’s methodology and parameter settings regarding insulation of walls

according to their orientation, figure 9 illustrates the total heating and cooling loads per square meter of insulating each direction of the envelope walls separately.

In compact model, insulating eastern wall has recorded maximum reduction in total loads by 6%. While insulating western wall has reduced total loads by 2%.

In L-shape model, insulating eastern or western walls has recorded maximum reduction in total loads by 6%. While insulating south walls has recoded minimum reduction in loads by 2%.

110

115

120

125

130

No insul. North East South West

KW

h/m

2

Compact L-shape

Figure 9 Total heating and cooling loads for wall insulation alternatives according to orientation

Figure 10 illustrates the total heating and cooling loads per square meter of using code compliance parameters against optimized parameters concluded from previous stages of simulation as in table 1:

Table 1 Code compliant / optimized parameters Code Compliant Optimized Roof U = 0.3 U= 0.4 North wall U = 0.76 U = 0.9 East wall U = 0.6 U = 0.4 South wall U = 0.76 U = 0.9 West wall U = 0.6 U = 0.9 Windows Double G. In all

facades Double G. in eastern facade

405060708090

100110120130

Traditional Code compliant

Optimized

KW

h/m

2

Compact L-shape

Figure 10 Total heating and cooling loads for envelope parameter variants

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5- Renewable Energy Figure 15 illustrates the electricity generated by a 2.0m by 4.0 m solar collector installed on the roof of the building compared to the electric lighting consumption annually. The electric lighting follows a common usage profile and satisfies the code requirements as shown in figure 16. Lighting Simulation: Table 2 summarises the code requirements for different house’s spaces lighting in terms of LUX levels, minimum window to wall ratio WWR, projection factor PF and visible transmittance VLT.

Table 2 Egyptian code lighting Requirements

PF=70o VLT=> 60%

Space Lighting Level (Lux)

Max. Avg. Min. Min. WWR

Bedroom 100 75 50 15%

Living 500 300 200 15%

Kitchen 400 200 100 10%

Bath 200 150 100 10%

Corridor 200 150 100 n/a

Table 3 compares the results of lighting simulation for code compliant shading parameters against the base case.

Despite the fact that shading devices - as per code parameters and specifications - have reduced effectively the excessive lighting and glare into spaces, the results show that the shading devices have lowered minimum and average lighting levels below those specified by the code itself.

Table 3 Egyptian code lighting Requirements

Mod

e

Cas

e

Spac

e Daylight level (Lux)

Avg. Min. Max.

With

out S

hadi

ng

Com

pact

Bedrooms 355 120 1420 Living 534 210 1410

Kitchen 282 100 700 Bath 172 55 555

L-sh

ape Bedrooms 335 120 1420

Living 528 180 1380 Kitchen 279 90 690

Bath 224 65 765

Shad

ing

as p

er c

ode

PF=7

0o Com

pact

Bedrooms 281 50 1050 Living 427 150 1250

Kitchen 214 50 550 Bath 135 50 450

L-sh

ape Bedrooms 279 55 955 Living 429 140 1240

Kitchen 213 60 560 Bath 178 45 545

Figures 11, 12 and 13 illustrate day-lighting levels in living space in both of compact and L-shape models.

Using 10% WWR has recorded minimum lighting levels that are less than the values specified by the code.

Figure 11 Lighting levels of living space in compact

model (right) and L-shape mode (left) using WWR=10%

Using 20% WWR has achieved acceptable minimum values, however it has exceeded maximum acceptable values.

Figure 12 Lighting levels of living space in compact

model (right) and L-shape mode (left) using WWR=20%

Using 30% WWR has recorded minimum values that are close to the maximum values specified by the code.

Figure 13 Lighting levels of living space in compact

model (right) and L-shape mode (left) using WWR=30%

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RESULTS The form of the building is playing an

important role in reducing total heating and cooling loads since compact model has recorded consumption values less than the L-shape model in all simulation runs.

The roof insulation has been found the most important parameter in reducing total heating and cooling loads in a single-family housing unit regardless of its form.

Insulating exterior walls with 2cm EPS is more efficient than using 6cm or 8cm EPS, from an economic point of view.

Common usage profiles for each space for a housing prototype is playing a key role in assigning insulation parameters.

Using R-values for an exterior wall according to its orientation seems to have inefficient results with regard to energy consumption.

Windows code parameters should be defined through an integrated policy towards both of day-lighting and thermal comfort.

Simulation tools can be used to define an optimized set of parameters for each housing prototype in each climate region, which can be consequently more efficient from an economic point of view.

Defining envelope parameters from energy efficiency criteria, economic point of view and availability in the common construction market could have a major effect in enhancing ERBEC with regard to the ease of use and application in a developing country like EGYPT.

Integrating the use of Renewable Energy RE sources in ERBEC in addition to illustrating its benefits are considered vital to reduce the total dependency on fossil fuels as an energy source and therefore mitigating the negative impacts of global warming and climate change.

CONCLUSION A Roadmap for enhancing Residential Buildings Energy Code in Egypt is developed and the aspects through which energy simulation software can play a major role in enhancing Egypt Energy Code for Residential Buildings are recommended as shown in figure 14, The goal of these guidelines is to make a tailored code that is easy to use and implement in the Egyptian construction market. 1- Code structure and organization:

Restructure the code according to the latest energy efficiency criteria,

Integrate the use of Renewable Energy sources RE,

2- Compliance paths: Update existing compliance paths, Developing compliance parameters

dedicated to unique residential buildings prototypes such as Single-family, Low-Rise Apartment blocks and high-rise apartment blocks,

Create a compliance method that could be integrated easily into the design by local construction practitioners,

3- Compliance parameters and equations: Update the code with materials, devices and

equipment properties that are widely available to the construction market in Egypt,

Defining the most important envelope element that could play a major role in reducing total energy consumption of the building,

Redefine electrical lighting fixtures according to both their availability in market and their efficiency in reducing energy consumption in buildings,

Reformulate equations for calculating sun-shading devices,

Consider usage profiles in the process of defining parameters values,

Redefine the best set of parameters for each climate regions,

Figure 14 Aspects revisited through the paper

ACKNOWLEDGEMENT We would like to acknowledge and extend our gratitude to the following persons who have made the completion of this research paper possible: Prof. Dr. Adel Deif, Dean, Faculty of Engineering, University of Mansoura. Prof. Dr. Esmat El-Attar, Chair, Department of Architectural Engineering, University of Mansoura. Eng. Mamdouh El Menshawy, Department of Architectural Engineering, University of Mansoura. Mr. Ahmed Helmy, MSc, University of Greenwich. Mr. Karim Shehata.

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Figure 15 Electricity generated by solar collector compared to electric lighting energy consumption

Figure 16 Electric lighting levels in compact model

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