Carlo Alberto Amadei

Aleksejs Prozuments

Development of sustainable building Single family house Internal report

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Abstract

The main purpose of this paper was to design a sustainable single family house. Product development methodology was used to determine priorities, establish the engineering characteristics that the considered system should have to ensure. The house is partly prefabricated in order to have the most efficient cost effect and reduce the pollution from the construction site. House components were chosen according on their low heat transfer coefficient and overall energy performance. European standards for class II EN 15251 were used as a basis of the comfort levels of indoor temperature, air quality and day light factor. For the energy consumption calculation was used IESVE. In order to achieve yearly consumption of 20 kWh/m2 several components of the building envelope, ventilation system and heating system were analyzed; particular attention was paid to the geometry of the building too.

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Nomenclature ......................................................................................................................................... 6

1. Introduction ..................................................................................................................................... 7

2. Product development ...................................................................................................................... 8

3. Design of a sustainable house ........................................................................................................ 10

3.1 Geometry ............................................................................................................................... 10

3.2 Building envelope ................................................................................................................... 11

3.2.1 Wall ................................................................................................................................ 11

3.2.2 Roof................................................................................................................................ 12

3.2.3 Floor ............................................................................................................................... 13

3.3 Windows ................................................................................................................................ 14

3.4 Doors ..................................................................................................................................... 15

3.5 Ventilation system ................................................................................................................ 15

3.5.1 HVAC unit .............................................................................................................................. 16

3.6 Heating system....................................................................................................................... 17

3.7 Domestic Hot Water ............................................................................................................... 18

3.8 Electricity to run pumps ......................................................................................................... 20

4 IESVE simulation ................................................................................................................................. 21

4.1 ModelIT ....................................................................................................................................... 21

4.2 Apache ......................................................................................................................................... 21

4.3 Apache HVAC ............................................................................................................................... 22

4.4 Macroflow ................................................................................................................................... 24

4.5 Vista and result ............................................................................................................................ 24

5 Cost of conserved energy .................................................................................................................... 26

5.1 Economically optimized design of the reference building ............................................................. 26

5.2 Windows ...................................................................................................................................... 26

5.3 Wall, roof, floor ............................................................................................................................ 30

6 Conclusions ........................................................................................................................................ 35

Problems ........................................................................................................................................... 35

Results & Discussion .......................................................................................................................... 35

Suggestions ....................................................................................................................................... 36

7 References ..................................................................................................................................... 37

8 Appendix ....................................................................................................................................... 39

Contents

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Appendix A. ....................................................................................................................................... 39

Establishing the functions of product attributes. ............................................................................ 39

Determination of engineering characteristics ................................................................................. 40

Appendix B. Condensing boiler data ................................................................................................... 40

Appendix C. Indoor Environment ....................................................................................................... 41

9 Individual work .............................................................................................................................. 42

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NomenclatureA: area (m2) m: mass of water (kg); c: specific heat capacity of water (kJ/kgK); ∆T: difference between supply (hot) and influent (cold) water temperatures (K). U: thermal transmittance (W/m2K) λ: thermal conductivity (W/mK) Iperson per area: internal gain person (W/m2) Iperson : internal gain person (W/person) Iequipment : internal gain equipment (W/m2) Itotal: total internal gain from people and equipment (W/m2) EDHW: energy for domestic hot water (kWh/m2) ETOT: total annual energy consumption (kWh/m2); EFAN: energy consumption of fans (kWh/m2); ECOOL: energy consumption for cooling (kWh/m2); COP: coefficient of performance for cooling (kWh/m2); EDHW_PUMP: energy consumption of the domestic hot water pump (kWh/m2); EHEAT_PUMP: energy consumption of the heating system pump (kWh/m2); EHEAT: energy consumption for the heating (kWh/m2); CCE: cost of conserved energy a(n,d): factor of recovery rate [d/(1-(1+d)-n)]; Imeasure :additional cost of energy conserving measure (monetary unit, €); ∆Eyear :annual energy conserved by the measure (kWh)nr :reference period (years); nu :useful lifetime (years); d :real interest rate (%) t :nr/nu ratio E :window net energy gain (kWh/m2) 196.4 is a total solar radiation during the heating season (kWh/m2); 90.36 is a total degree hours based on DRY (kKh); g: total solar energy transmittance, EN410 (centre value); U: total thermal energy transmittance of the window, EN ISO10077-1 (W/m2K). Φ : annual energy use of the construction (kWh/m2); λ :thermal conductivity of the construction (W/mK); d : thickness of the construction (m), Dh: number of degree hours in the heating season (kKh) ∆Myear: difference in investment cost distributed as annual cost (€/years); ∆Eyear: difference in annual energy consumption related to the reference (kWh);

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1. Introduction Buildings account for 40 % of total energy consumption in the European Union. The sector is expanding, which is bound to increase its energy consumption. Therefore, reduction of energy consumption and the use of energy from renewable sources in the buildings sector constitute important measures needed to reduce the Union’s energy dependency and greenhouse gas emissions. In January 2008, the Commission published the 20 20 by 2020 package. This includes proposals for reducing the EU’s greenhouse gas emissions by 20% and increasing its proportion of final energy consumption from renewable sources to 20% by 2020. With the new European building directive (European Parliament and Council, 2010), there is the effort to go further the last directive, in order to have a decrease of overall greenhouse gas emissions by 30 % (in the event of an international agreement being reached) and to reach a nearly zero energy building. The nearly zero or very low amount of energy required should to a very significant level be covered by energy from renewable source, including renewable energy produced on-site or nearby. Since the single family houses are part of this the aim of this paper is the design of new single family house with a yearly heating load for the space heating of 15 kWh/m2 and a total energy consumption of 20 kWh/m2, in order to support the develop of zero energy building. To reach the mentioned energy consumptions is required to work on several aspects such as: -geometry of the house; -insulation of the building envelope; -window (heat losses, geometry, orientation, solar gain and visual transmittance); -ventilation system; -domestic hot water; -heat supply system; Firstly was used a product development methodology to determine what aspects of designing a product are most important for its function. The starting point was the design of a proper building geometry, then is important to figure out which materials use for the building envelope (windows , walls, floor and roof) and their thermal properties. The ventilation system was designed taking into account pressure drop and heat exchange efficiency (the flow rate is assumed to be 0.5 h-1 and a flow rate infiltration - 0.05 h-1). According to the ventilation system and dwelling characteristics a heating system was designed. Last step is the calculation of the energy performance of the building in IESVE. In the latter software there are several applications: -ModelIt: to design building component; -Apache: for the preparation of input data for thermal analysis, program specification of the building location and weather data, calculations and simulations; -Apache HVAC: modeling heating, ventilating, and air-conditioning (HVAC) systems, and falls within the Virtual Environment’s Thermal category; -Macro flow: MacroFlo is a program for analyzing infiltration and natural ventilation in buildings; -Vista: for analyze the results. After the simulation an accurate analysis of the result is required to control the thermal indoor environment according to class II EN 15251. The following chapters outline and explain the procedures, calculations and associated results of trying to achieve a low energy consuming office building with a low energy ventilation system through product development methodology.

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2. Productdevelopment

To describe the conception of the low energy building model it is recommended to define the key issues in stepwise manner. As the requirements for the low-energy buildings are strict it is necessary to look through strategic solutions of the product development. The first stage is to clarify objectives what would the prospective system is going to perform from the view of the customer. The principle is to demonstrate goals by connecting the factors representing the system performance, with number of other factors (customers, composition of the system, engineering characteristics). Further we are focusing on the most significant attributes. Subsequently it is possible to establish functions and set requirements. According to them engineer can build up a draft or conceptual model of the building energy system sources, alternatives and solutions. To represent customer demands, to analyze interactions between different parameters of product attributes engineering characteristics should be determined. This part is the most important for engineer as the guideline for the whole project. According it engineer can estimate how strongly varies in one engineering characteristic affect others. Aforementioned comparisons and accurate analysis is coming up with an optimal solution of the designed system. It is worth to run through the model and to study more alternatives to improve details and overall performance of the system. Eventually the project is ready to be implemented.

Table 1: Evaluation of customers’ interest rate with respect to product attributes

The table 1 and numbers below indicate the product attributes we should focus on. Numbers represents the sum of the marks stated for each customer. As the main objective of low energy house dominates low energy consumption. It can be achieved with a well insulated building envelope and high performance windows together. If one of the components has an air leakage or other insulating defects

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the good performance of the second component does not make any sense. As the following important aim where to focus on is the durability of each construction. The lifetime is just a relative guideline for the durability of particular component but each construction should keep its initial properties as long as possible and engineer has to find the best conjunction of materials to make it both sustainable and attractive. As one of the aims was to find the prefabricated components (wall, roof and floor constructions) since it is in accordance with a low energy statement (prefabricated structures requires much less in situ work, has a lower market prices and perhaps have less industrial effect – impact on the environment). Since the projected building is a single family house and residence time is nearly 100% during weekends and 70% during weekdays the next important issue is a good indoor environment and high air quality. This implies sufficient heating during the cold season and avoidance of overheating during the summer. The figure 1 shows the chart of where all priorities of our designed house are distributed in the descending manner. The figure also explains which of customers and at which scale are interested in the particular product attribute.

Figure 1: Chart determining the priorities of designed building

Some notes how to make an interpretation of the figure. Engineer is responsible; user (family) and owner (family) are concerned about building energy performance and high comfort level. Durable building with low energy consumption means less demand for fossil fuels therefore it plays role on society attention.

Establishing functions: We have evaluated in 5 grade scale how the engineering characteristics affect those product attributes. In the table (Appendix A) is expressed overall function of design. Many alternative components are capable of performing the identified functions.

Determining characteristics: The aim of the quality function determination was to set targets to be achieved for the engineering characteristics of a product such that they could satisfy customer requirements (Appendix A).

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Evaluating alternatives: The aim is to generate the alternative design solutions for a product (single family house). Our alternatives are described in chapter 5 where cost of conserved energy (CCE) is analyzed depending on improvement of product energy performance.

3. DesignofasustainablehouseIt has been chosen to deal with a new building for two main reasons: -the renovation of a building may cost more than the construction of a new building. -the design of a new building allows playing more with the geometry of the building (Chapter 3.1)

3.1 GeometryThe geometry of the building has a great influence in the energy consumption of the building, especially in the creation of thermal bridges and exposed surface. The geometry (as it can be seen in figure 2) is nearly a cube because between all the geometries the cube has the least surface an area with the same volume (except the sphere).

Table 2: Rooms specification

Figure 2: Single family house layout

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Figure 3: Single family house plan (1st floor – left, ground floor - right)

3.2 BuildingenvelopeThe house is partly prefabricated (wall and roof) in order to have the most efficient cost effect and reduce the pollution from the construction site.

3.2.1 WallThe prefabricated wall is produced by Kofinas Procat-prefabricated house. The U value declared is 0.11 W/m2K and the cost is 140 €/m2 plus + the cost of the exterior thermopsosopsis system (external EPS 80 and acrylic plaster) and plus the cost of internal plaster (Kofinas). The wall has a thickness of 35 cm which is broaden in this paper to 37 cm with an external layer of wood to be more in accordance with Danish market; the structure of the wall is shown in figure4.

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Figure 4: Prefabricated wall construction layout produced by ‘Kofinas’.

3.2.2 RoofThe prefabricated roof is produced by Kofinas Precast-prefabricated as well. The U value declared is 0.125 kcal/m2h°C(Kofinas), which is equal to 0.18 W/m2K. The roof has a thickness of 32 cm and its structure is shown in figure 5.

Figure 5: Roof layout designed by ‘Kofinas’; thickness values are based on this layout.

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Figure 6: Roof layout from the web page of ‘Kofinas’

3.2.3 FloorFor the floor were evaluated two different solutions (figure 7 and 8); both of them allow placing a heating system from the floor. Since our prefabricated construction has a low thermal mass, the second solution (figure 8) has been chosen; indeed in this solution the insulation material is placed more underneath the concrete slab compare to the first solution, then it represents a higher increase in the total thermal mass of the building. The u value of the floor is 0.10 W/m2K.

Figure 7: Floor construction

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Figure 8: Floor construction (increased thermal mass)

Floor construction is selected to have a thick concrete layer in upper part because of its potential to store and re-release thermal energy. Thermal mass acts as a thermal battery. During summer it absorbs heat, keeping the house comfortable. In winter the same thermal mass can store the heat from the sun or heaters to release it at night, helping the home stay warm.

In assistance with under floor heating concrete slab shows a good performance of indoor climate. Because the heat source is at the feet, the perceived comfort level is greater. As a result, actual room temperatures can possibly be one or two degrees below those required with other systems – resulting in energy cost savings.

3.3 WindowsThe windows must retain heat and let as much solar energy enter the house as possible so the windows must use low energy glass and thermally insulated frames.

As a best solution for windows was found the product of Internorm Triple White Glass Solar. It is a three-pane-glass with a krypton gas filled between glazings. Triple white glass SOLAR is characterized by the combination of the special layering system SOLAR and extra white float glass. The triple insulation glass exhibits extremely high heat insulation, as well as a degree of total energy penetration (g-value) that could normally be realized in this amount with double glazing only. Due to this special relation between Ug and g-values, this glass is perfectly suitable for the realization of solar constructions. It utilizes weak solar radiation optimally especially during winter and cold months and retains the heat within the building. The high value enables the optimal acquisition of passive solar energy when building conditions are poor or the direction of the glazing (South) toward the sun is inexact.

Technical data showed high performance of the window heat transfer with U value of 0.71 W/m2K and total solar energy transmittance g = 60%. (Internorm Technical data D&B). As the following factor was a

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great suitability for Danish design requirements due to its light structure with wooden frame. Window model is shown in figure 9.

To make a product optimization method of cost of conserved energy was managed. Therefore we had compared 4 types of windows and Internorm appeared as the most optimal one. The procedure of this optimization is described in chapter 5.

Figure 9: Image of ‘Internorm’ windows Figure 10: Image of ‘Internorm’ doors

3.4 DoorsThe two doors placed in the technical room and in the living room (ground floor) are produced by Internorm (Internorm, 2010). The U value is 0.70 W/m2K. The door construction is a combination of wood/aluminum/thermal foam, plywood and phenol panel layers ensures great stability, even for the worst weather conditions (figure 10).

3.5 Ventilationsystem Mechanical ventilation and natural ventilation through external window for the cooling during the summer were used. The intake and outtake are place in the East side of the house at different height to avoid mixing of fresh and exhaust air; a difference in height of 2 .5 meter can avoid this mixing. The core of the ventilation system is placed in the technical room where the main duct radiates out from the room and where the principal components as heat exchanger filter and fans are placed. In order to avoid possible noise of the airflow, fresh air is provided in each room individually, where is also placed an exhaust devices; the flow rates are set to be 0.5 h-1 (Svendsen, 2010) except of the bathroom and the kitchen where the flow rate is set to 15 l/s and 20 l/s respectively (table 3). The exhaust and supply ducts are placed in suspended ceilings. Also heating and cooling coil are inserted, which characteristics are explained in chapter 4.3.

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Table 3: Flow rates

The infiltration rates are set to 0.05h-1 and they can be seen in table 3. Table 4: Infiltration rates

3.5.1HVACunitThe HVAC unit is represented by RecoupAerator® 200DX (UltimateAir). The 200DX is an Energy Recovery Ventilator (ERV), meaning that the RecoupAerator captures temperature and moisture from the stale, outgoing air and transfers it to the incoming air stream. In addition to having an energy transfer rating of up to 95%, the RecoupAerator moderates indoor humidity in the winter and turns away outdoor humidity in the summer (UltinateAir, 2006). The main characteristics of this HVAC are: -automatically self-balances air flow; -95%+ heat recovery efficiency; -95% filtration at 1.8 microns (MERV 12);

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-up to 75% moisture transfer capability (depending on season); -whole-house air exchanges; -compatible with many IAQ monitors and fans; -automatic frost prevention down to -20 °C; -variable speed; -no drain required; -filter service indicator; -fully insulated.

Figure 11: Recoup Aerator 220DX

The pressure drop of the system are set to 25 Pa (illustration in figure 11 (UltinateAir, 2006)), which are split in 15 Pa for the supply fan and 10 for the exhaust fan.

3.6 HeatingsystemThe heating system is provided by a condensing boiler, placed in technical room. A condensing boiler extracts additional heat from the waste gases by condensing this water vapor to liquid water, thus recovering its latent heat. A typical increase of efficiency can be as much as 10-12%, and it can reach efficiency more than 100%; the effectiveness of this condensing process varies, it depends upon the temperature of the water returning to the boiler, but for the same conditions, it is always at least as efficient as a non-condensing boiler (Wikipedia, 2010). Usually the waste gases of a traditional boiler are expelled at temperatures around 110 °C. The temperature of the gases expelled by a condensing boiler has a range between 40 °C and 55 ° C; it is evident that the recovery of useful heat is remarkable. This recovered heat reduces the demand for fuel that the boiler has to spend to heat the water plant. Then, is possible to understand why, with the usual formulas for calculating the boiler efficiency, the yields are higher than a condensation of 100% (it may surprise the yield quoted more than 100%). In order to optimize the performance of a system based on condensing boiler, it is required to use a system with lower return temperature and this can be achieved with extensive and efficient radiant surfaces. The ideal temperature for the system design, supply and return, are equal to 40/30 °C. In the case of a plant at high temperatures with conventional heating, the design temperature will be higher, indicatively equal to 75/60 °C. Under these conditions, the water vapor cannot release heat to the fluid. It is for this reason that the major advantage in terms of savings can be found on the under floor heating system,

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where the temperatures of the system are available, ranging from an average of 40/30 °C. There are many benefits of using under floor heating as opposed to traditional heating methods, please see the list below: -comfort (figure 12): the temperature at the floor level is at that comfortable range while the temperature at head is lower but still at a very comfortable temperature. The heat radiates up from the floor, warming all the objects in the room. Everything in the room will gain a nice, warm, comfortable feel to it. As documented by ASHRAE, local thermal comfort is determined by the vertical air temperature difference between the feet and the head, by an asymmetric radiant field, and by a local convection cooling (draft), or by contact with a hot or cold floor. With radiant floor heating, heat is kept where it is needed (at the floor). This keeps occupancy more comfortable (even at a lower temperature setting) because when humans’ feet are warm, it feels warmer. The heat distribution in a room is optimal when the temperature is higher at the feet than at the head level; -space saving: under floor heating is out of sight and therefore out of the way, giving you extra space and allowing you to furnish rooms as you like; -aesthetics: under floor heating is out of sight; -silence: under floor heating suffers none of the creaks or groans of conventional copper pipes and radiators, just a reassuring silence; -health and hygiene: under floor heating prevents dust mites living in carpets.

Figure 12: Thermal indoor quality (temperature dependence)

For the reasons explained above, was chosen the solution with condensing boiler produced by Immergas combined with water pipe heating under the floor; since the low temperature system the efficiency is 108%. All the data of the condensing boiler, which costs about 1500 € are reported in Appendix B. (Immergas, 2010).

3.7 DomesticHotWaterTo provide inhabitants with domestic hot water (DHW) requires considerable energy consumption. In this chapter we have analyzed the energy use of boiler to heat the water (energy consumption for pumps is not included). As the source could be methane gas or electricity.

Total heat energy E (kJ) necessary to heat up water can be calculated through following equation:

𝐸"#$ = 𝑚 ∗ 𝑐 ∗ ∆𝑇; (1)

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It is stated that in household conditions hot water temperature has to be heated to 55 oC whereas influent temperature from water supply network is 10oC.

Mass of water m (kg/yr) required to be heated up during the year can be calculated after the hot water consumption per person is figured out. In single family house the main uses of hot water are for bath, shower, hot water drawn from the tap, hot fill washing machines and dishwashers. The amount of water consumed by these operations is difficult to predict, therefore statistical data from British research were collected (BRE Housing Centre on behalf of DTI and DEFRA,2005).

Figure 13: Estimates of hot water consumption (1998 EFUS)

Figure 13 was used as a source to determine hot water consumption per person per day. Since the house was designed for 4 people the amount of hot water usage was taken 52 l/day/person. Following assumptions were taken into account:

- during the daytime (8.00 – 18.00) in weekdays people are outside the house and consuming water being inside other premises;

- there are not included holidays or trips when there is absence of people for a longer period;

- during summer season hot water demand significantly decreases

Thus significant amount of water usage can be subtracted from the value taken from the figure 13. We assumed that above mentioned factors compose ~40% of overall demand (in the annual scale) therefore total DHW consumption was reduced to 30 l/person/day(that is an accordance to the consumption

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state in the assignment instruction 0.25 m3/m2). According to this annual DWH was calculated by multiplying daily consumption with 365 days of year. When all values were found total water mass was calculated according to the water density at 4oC (1000 kg/m3). Final power requirement for heating up the water is shown in table 5.

Table 5: Annual energy consumption for DHW

Since the low energy house requires low demand on heating energy consumption (15kWh/m2 including heating and DHW) we managed to decrease the total DHW consumption by 50% using solar water heating (SWH) collector system. The electricity (or gas) for heating up the water will be assisted by solar collector. The behavior of solar collector can vary – in sunny day it will cover all energy use for DWH, however, in the dark time (especially winter season) it will assist slightly.

3.8 ElectricitytorunpumpsTo provide a circulation and sufficient pressure additional electricity is necessary for pumps. It was stated that electrical power used for the pump in the heating system and in the solar heating system is 5 W each of them. Operating hours are all year for heating system and 1000 hours for solar heating system. Also electrical energy must be multiplied by a factor 2.5 since electricity is produced by significant combustion of fossil fuels. This process has a low ratio of desired energy with respect to input energy (a low efficiency).

Results of annual electricity consumption for heating system pump and solar heating system (SWH) pump are given in table 6.

Table 6: Calculations on energy consumption of pumps

Total electricity needed for pumps is 0.250 + 0.069 = 0.319 kWh/m2 yr which will be added to the total energy consumption.

Since it has been approached a single house family the electricity for the lighting was not taken into account.

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4IESVEsimulationIn order to calculate the energy consumption of the building and evaluate the indoor environment quality IESVE software was used. The detail explanation of the calculation procedure and assumptions is explained in this chapter; each sub-chapter is related to the utilized IESVE-application.

4.1ModelITIn this step the house was designed according to the AutoCAD drawings (figure 14); elements such as attic and the garage that would have had some positive effect on the final result are neglected; even if those environments are not heated, they can smooth the outside temperature, determining a benefit for the heating and cooling consumption. From figure 14 is possible to see that the kitchen is connected with the living room through a hole, as the bedroom 2 is connected to the studio.

Figure 14: ModelIT of the single family house

4.2ApacheIn this step all the building envelope elements were built; it was required to create elements such as window, external wall, main doors, ground floor and roof according to the U value and materials declared by the producer. Also were created wooden construction for internal ceiling and floors, internal partitions because even if they do not directly influence the energy consumption they could have influence on the result modifying the thermal mass of the house. In Apache were defined also several profiles for occupancy and equipment (related to internal gains). In table 7 is presented the supposed occupation time of the house; it was supposed that 4 people live in the house and the percentage in the table are related to this number. As it can be seen from the table during the weekdays there is no one at home from 08:00 to 18:00, because people are at work, school etc. In the weekend

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the situation changes and was defined a percentage of 80% from 08:00 to 18:00. In order to simulate the worst case no winter or summer holidays are taken into account.

Table 7: Occupation time of the designed house (expressed by percentage ratio, where 1 corresponds to 100%)

The internal gains due to persons and equipment can be set to 5 W/m2 (Svendsen, 2010).

The internal gain due to person is calculated:

𝐼-./012-./3/.3 =2456789∗:456789

;<= =∗>?

@A?= 2𝑊/𝑚E (2)

With a simple difference the internal gain duet o the equipment is 3W/m2.

𝐼.FGH-I.2J = 𝐼J1J3K − 𝐼-./012-./3/.3 = 5 − 2 = 3𝑊/𝑚E (3)

The internal gain due to the equipment follows a profile during the day: it starts at 10% during the night and reach 100% just from 18:00 to 24:00.

4.3ApacheHVACIn order to design the ventilation, heating and cooling system was used the HVAC application. In IESVE is not possible directly implement floor heating; it could be possible to create an extra room in the floor representing the pipes. As explained in chapter 3.5 the heating system is through floor heating but for the simulation traditional radiators are used.

The layout of the whole system is showed in figure 15, where each loop represents a room. From the figure 16 it can be seen the enlarged image on the main components of the system:

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1) Supply fan: flow 104 L/s, pressure drop 15 Pa, efficiency 85%

2-3) Cooling coil and its switch controller: the cooling coil is activated when the outside temperature is more than 16 °C

4-5) Heating coil and its time switch controller: the heating coil is activated when the outside temperature is below 10 °C

6) Time switch controller for the flow rate: temperature should be 24 °C ± 1 °C and the CO2

concentration 1000 ppm ± 50 ppm during the occupancy hour and one hour before the occupancy hour; in the other hours it is allowed to have a higher concentration of CO2.

7) Radiator

8) Extract fan: flow 104 L/s, pressure drop 15 Pa, efficiency 85%

9) Heat exchanger: efficiency 95% and it is activated when the outside temperature is below 15°C.

Figure 15: HVAC system

Figure 16: Zoom on the main component of the HVACX system

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4.4MacroflowIn order to minimize the energy consumption due to the cooling and the ventilation, the Macroflow application was used. In this application is possible to simulate natural ventilation through openings in the building envelope such as window (in this case all the external window can perform as an opening); with the natural ventilation which sets from 1st May to 13th September with different set temperatures depending on the month and the time.

4.5VistaandresultAll the results concerning the energy consumption and the indoor environment conditions are displayed in Vista application. The first results were not satisfying; there were problems in the quality of the indoor environment, such as overheating, under heating and high concentration of CO2. In order to solve these problems 3 different strategies were applied:

1) adjustment of the heating profile in order to reduce the hours of overheating;

2) emplacement of external shading in all the three bedrooms activated when the indoor temperature reaches 23 °C. In the south side was placed a hangover of 1 meter that can act s a balcony (see figure 2);

3) The high CO2 concentration took place especially in the three bedrooms during the night; in order to solve the problem the flow rate in these environments was increased and the new flow rate are reported in table

Table 8: new flow rate

With these strategies European standards for class II EN 15251 was reached; the results of the environment indoor condition are reported in Appendix B.

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Finally total energy consumption is the sum of the heating load, the losses1,2 and efficiency of the heating system3, the energy for the domestic hot water and the electrical energy used in the pumps and fans of the technical building services (heating and ventilation system, solar heating system).

𝐸OPO = Q𝐸R;S +𝐸UPPV𝐶𝑂𝑃

+ 𝐸"#$Z[\Z + 𝐸#];OZ[\Z^ ∗ 2.5 + (𝐸#];O + 0.5 ∗ 𝐸"#$)(4)

Where 0.5*EDHW – energy consumption for domestic hot water where 50% is covered by solar water heater (kWh/m2). The results are reported in table 9.

Table 9: total energy consumption

Table 9 is related to the IESVE file called house.

1Heat loss from domestic hot water pipes is zero as no circulation is used.

2Heat loss from heating system is zero as the pipes are inside the insulation of the building.

3Heating energy is produced in a central heating system by condensing boiler with great efficiency due to utilizing the latent heat.

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5Costofconservedenergy

5.1EconomicallyoptimizeddesignofthereferencebuildingDue to increasing constraints of fossil fuels energy resources and necessity to look after environment making energy performance is an important issue of new buildings. Implementation of a long term solution to eliminate problems related to use of fossil fuels by a combination of energy conservation and use of renewable energy is a challenge we have to encounter with.

The aim of the following part was to find the balance between the cost of conserved energy (CCE) and the cost of renewable energy.

𝐶𝐶𝐸 = 𝑡 ∗ 𝑎(𝑛, 𝑑) ∗ 𝐼𝑚𝑒𝑎𝑠𝑢𝑟𝑒/∆𝐸𝑦𝑒𝑎𝑟 (€/kWh) (5)

The annual energy use of the windows was described by the net energy gain, which is the solar heat transmitted in through the window, minus the heat loss transmitted out through the window during the heating season:

𝐸 = 196.4 ∗ 𝑔– 90.36 ∗ 𝑈 (6)

The annual energy use of the wall, roof and floor construction was calculated through with degree day method:

𝛷 = 𝜆/𝑑 ∗ 𝐷ℎ (7)

5.2WindowsTo perform an optimization 4 window types were selected (Table 8):

1) Internorm windows (Internorm technical data D&B.pdf page no. 27)with U = 0.71 W/(m2K), g = 60%; Guided by some examples, scientific paper (S.Petersen, S.Svendsen) and catalogues we have assumed that price for these windows could be 550 €/m2 window approximately.

2) Window type 1 we have simulated in the Assignment no. 1* with U = 0.6 W/(m2K), g = 52%; 3) Window type 2 we have simulated in the Assignment no. 1 * with U = 0.82 W/(m2K), g = 62%;

*We are not able to choose these types of windows as they do not exist yet, but they serve as a good guideline to make a comparison and optimization analysis. So we have assumed the approximate price due to their energy performance (g, U values and gas filling). Broxwood windows (http://www.broxwood.com/the-broxwood-alpine-range.html) with U = 0.6 W/(m2K), g = 53%; Guided by some examples, scientific paper (S.Petersen, S.Svendsen) and catalogues we have assumed that price for these windows could be 485 €/m2 window approximately as their energy performance is a bit lower. Lifetimes of windows assumed to be 30 years as it is in common.

These all are representing good solution for low energy buildings and passive houses and according to them our aim was to find the best one from both economical and energy saving point of view.

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Table 10: Technical data, costs and CCE of analyzed windows (Step 1)

Energy use of window (kWh/m2) is the opposite of energy gain (kWh/m2). Calculations of CCE (cost of conserved energy) were made according to equation 5.

In the introduction to the following steps of optimization analysis some basic assumptions were made:

- reference period (40 years) to ensure a fair frame of reference for comparison of energy conserving measures with various useful lifetimes;

- real interest rate (2.5%).

A procedure for the computational establishment of a function was based on discrete measures according to following steps:

STEP 1: The annual energy use of each window was calculated (table 10). The component with the lowest cost was chosen as a reference (figure 18).

Figure 17: Cost versus energy use (Step 1)

STEP 2: The CCE of remaining components was calculated with respect to the reference (Windows type 2). Calculations were based on equation 1:

𝐶𝐶𝐸 = (𝑡 ∗ 𝑎(𝑛, 𝑑) ∗ 𝐼𝑚𝑒𝑎𝑠𝑢𝑟𝑒 + ∆𝑀𝑦𝑒𝑎𝑟)/(∆𝐸𝑦𝑒𝑎𝑟 + ∆𝐸𝑦𝑒𝑎𝑟) (€/kWh) (8)

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As it was stated that no component with the negative CCE would ever be economically efficient andshould be rejected we had to consider it by making some modifications. If the reference point (Windowstype 2) CCEWRT_REF value would be moved to 0 point as a reference – starting point (figure 18, table 11) than all CCEWRT_REF of other windows would be with negative values and therefore should be rejected (since other windows have lower CCEWRT_REF values). This would make the procedure without logical continue, without possibility of making any optimization. Due to this we made a window with the lowest CCEWRT_REF as a starting point 0 to avoid negative values. This is applicable operation because the reference point remained the window with the lowest cost (€/m2).

Table 11: CCE table of analyzed windows (Steps 2, 3)

Figure 18: CCE versus energy use (Step 2)

STEP 3: The window component with the smallest positive CCE value was recorded and set as a new reference. All components with an energy use higher than the new reference are not energy conserving measures and therefore were rejected. Therefore our first reference point represented window type 2 was excluded (figure 20).

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Figure 19: CCE versus energy use (Step 3)

STEP 4: The same procedures were made and plotted to the graph (figure 21) where optimal solution was found. The point having the lowest CCE (€/kWh) and the lowest energy use (kWh/m2) is represented by windows produced by Internorm therefore we have already simulated the optimal windows solution in design of the low energy house.

Table 12: CCE table of analyzed windows (Step 4)

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Figure 20: CCE versus energy use (Step 4)

Although the cost of the Internorm windows were assumed as the highest (550 €/m2) due to their high energy performance (relatively higher g value and rather low U value) Internorm windows showed the lowest values of both the energy use and CCE.

Simulations in IESVE were performed using directly these windows.

5.3Wall,roof,floorWall construction is described in chapter 3.2.1

Roof construction is described in chapter 3.2.2

Floor construction is described in chapter 3.2.3

The aim of this part was to find the best solution for above mentioned constructions. The idea is the same as for windows – to find solution for lower energy use with respect to lower costs. But the procedure contains by adding extra thickness to insulation layer with step of 0.05m.

As the actual costs for insulating materials was hard to find we made a comparison method. The price of the mineral wool was found in the website of Roxul AFB Mineral Wool producers. Although that wool is produced primarily for the acoustic insulation the prices for thermal insulations are supposed to be the same or close to the same. Prices were given in USD units per fixed dimensions of 24x48x2 inches. We considered it as a ratio of price (8.59 USD) per volume (24x48x2 inches) and converted units to € per 1m3 (table 11). As the thickness of insulation layer is 0.2 m for roof and floor and 0.1 m for wall we expressed the price per unit of area with thickness of 0.2m (€/m2 0.2m). Before implementing this procedure we had discussed with Cristian Anker Hviid due to his competence whether that method is admissible.

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Table 13: Method of estimating the cost of insulating material

The mineral wool is used as insulation material in roof construction so the value of 35.83 €/m2 (with thickness 0.2m) is applicable for the construction.

As it is shown in table 12 and 14 for the wall and floor construction other insulating materials were used – expanded polystyrene (EPS) and high durability polyurethane (PU) correspondingly. Therefore prices are changing. As it is shown in Figure 21 (Spray insulation,2007) the cost of EPS can be assumed as ~60% of mineral wool cost, so it was considered as 0.6x35.83 = 21.50 €/m2 (with thickness 0.2 m). As the initial thickness of insulating layer of prefabricated wall construction is 0.1 m, the price goes down to 21.5/2 = 10.75 €/m2.

Figure 21: comparison of insulation cost

The price of polyurethane insulating material is considered to be higher than previous both since it has to perform not only high thermal insulation properties but also high durability, high resistance to weight loads (since it will be placed below concrete slab (Chapter 3.2.3)) and moisture resistance. Based on this we assumed the price as 45 €/m2 (with thickness 0.2 m).

Related procedures are shown in following tables 12, 13, 14. The U-values and thicknesses of whole construction and insulation layer separately (for wall, roof and floor) have to be in agreement with IESVE. The number of degree hours Dn(t) was based on the Danish design reference year which equals

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90 kKh for wall and roof and 63 kKh for the floor. Ordinary lifetimes of insulating materials are 150 years. Energy use (kWh/m2) was calculated according to equation5. CCE (€/kWh) was calculated according to equation 7.

Table 14: Data on energy use and CCE performance by adding extra insulation layer to wall construction

Table 15: Data on energy use and CCE performance by adding extra insulation layer to roof construction

Table 16: Data on energy use and CCE performance by adding extra insulation layer to floor construction

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Eventually CCE as a function of energy use was plotted for all constructions (figure 22). The optimized solution can be observed where curve has a most sharp bend – mathematically it is the critical point which is expressed as tangent of the curve. The values of these points are presented in table 15.

Figure 22: CCE as a function of energy use for wall, roof and floor

Table 17 shows how the additional insulation layers affect the total heat transfer coefficient. The U-value (W/m2K) of wall construction decreased from 0.11 -> 0.08, roof construction – 0.18 -> 0.12, floor construction 0.10 -> 0.07.

From the economical point of view it contributes to much higher investment costs but due to the high benefit of energy savings and durability of constructions it is undoubtedly justified.

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Table 17: Output of optimized insulation thicknesses for wall, roof and floor

Afterwards simulation with optimized insulation thicknesses was performed and consequently energy consumption was decreased according to formula 4. The results are reported in table 18.

Table 18: energy consumption according to CCE

Table 18 is related to the IESVE file called house_CEE.

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6Conclusions

ProblemsReaching an optimal indoor environment condition requires a lot of effort and time, because good energy consumption was required at the same time. The balance between indoor quality and low energy consumption required some strategies such as shading devices for the bedroom, overhang for the south side, changing the flow rates in the bedroom and designing a different heating profile for each room.

In order to establish a method for economically optimized building design we had encountered a serious challenge to find the prices of single components, constructions and windows. Often manufacturers do not publish the costs of their product due to their variable fluctuations caused by different external factors. Therefore we used some empiric methods based on comparisons and reasoned assumptions which were preliminary discussed with teaching assistants. Perhaps the methods do not give exact results but they definitely served as a guide to make the right decisions.

Results&DiscussionAs it can be seen from table 9 the aim has been reached. Indeed the energy consumption of the designed house is 20.81 kWh/m2y and for the heating 13.03 kWh/m2y. Above all the construction is based on real existing products such as the building envelope, HVAC unit and condensing boiler; keeping the design of the house close to reality was one of the main purposes of this paper. CCE analysis was used to find the optimal building envelope, especially concerning the thickness of the insulation material. With the latter solution the energy consumption was decreased to 16.08 kWh/m2y. Even if this solution represents the most cost effective solution, it is still necessary to talk with the producer if it represents also a feasible solution.

Adding more insulation to the wall, floor and roof construction (0.15 m extra layer) resulted in an increase in investment costs (€/m2) but considering the lifetime of constructions (150 years) this investment will certainly pay off much earlier. The gains of energy savings make the additional investment costs more than reasonable.

The short lifetime of windows (30 years) with respect to the reference period (40 years) it is an issue that needs more discussion. The price of Internorm was assumed to be higher compared to other window types (due to the higher solar energy transmittance and krypton gas filling which is more expensive then argon) as it was not possible to find the actual prices and unfortunately unsuccessful when trying to make contact with producers. Therefore the prices should be considered as a rough approximation and probably the price would be even higher (or lower). But it is obviously from chapter 5 that the annual energy use and cost of conserved energy (with respect to the reference window) make this type of window the most suitable to use in a low energy house.

To make the best passive solar heat gain, we have designed the geometry and orientation of windows that the sunlight could pass through windows in winter when there is a need for heat input, but the windows should ideally not be directly affected by sunlight in summer. This was achieved by having the

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large glazed panels facing south and building them under a wide overhang. East, west and north facing windows were designed only to be as large as necessary to achieve optimal light entry.

SuggestionsUsing weather predictive controllers and setting the assumed occupancy time makes heating and ventilation systems work automatically. It is hard to predict inhabitants’ behavior in exceptional cases (illness, feast days, parties) when residence time may vary considerably. Due to this it is proposed that occupants are able to regulate the pattern of the system according to their demands.

Regarding summer season when there is a high risk of overheating inhabitants should act in a manual way by opening windows:

- to exchange the air; - to implement the venting (keep some windows slightly opened during the night).

At night when the outdoor temperature drops, the stack caused by opened windows will be exploited to create night ventilation without help of fans. Venting will provide sufficient and free cooling. Another advantage of this will be usage of the thermal mass of the ground floor concrete deck. Thermo active concrete deck significantly reduces the need for air cooling. With the onset of the morning thermal mass of the concrete deck will remain pre-cooled temperature (from the air during the night) and provides freshness and comfort during the daytime. Towards the evening the concrete deck will be heated by the daytime air and with the drop of air temperature during the night it will be cooled again.

To reduce the risk of overheating, some bushes or trees can be planted in the yard on the southern side of the building. They will serve as additional shading in the summer. The tree has to be high enough and deciduous, but they must not create as shadow in photovoltaic or solar panels. Deciduous trees are naked during the winter season when the angle of sunlight becomes sharper therefore letting the sunlight reach the rooms. This natural shading will reduce g-value just in the summer season and not in the winter making it work in our favor.

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7 ReferencesEuropean Parliament and Council. (2010). DIRECTIVE 2010/31/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL.

BRE Housing Centre on behalf of DTI and DEFRA(2005).Estimates of hot water consumption from the 1998 EFUS.Implications for the modelling of fuel poverty in England European commission climate change,(2010). Analysis of options to move beyond 20% greenhouse gas emission reductions andassessing the risk of carbon leakage Internet resources:

Ashrae. ANSI/ASHRAE Standard 55-1992 R. 1992.

BroxWood. (2010). http://www.broxwood.com/the-broxwood-alpine-range.html.

DEFRA., B. H. (2005). Estimates of hot water consumption from the 1998 EFUS.

floor, S. w. (u.d.). Step warm floor...a step ahead. Hentet fra http://www.warmfloor.com/content/view/57/162/.

Immergas. (2010). VICTRIX 26 - ND:PRD_TECNICA.

Internorm. (2010). A glass design and build.

Internorm Technical data D&B. (u.d.).

Kofinas. (u.d.). http://www.kofinas.gr/main.php?l=2.

ltd, S. i. (2007). http://www.spray-insulation.co.uk/Insulation_material_comparison.htm. Hentet fra Spray insulation ltd.

Svendsen, S. (2010). Assignment 3 :Development of sustainabel building.

UltimateAir. (u.d.). http://www.ultimateair.com/. Hentet fra UtimateAir.

UltinateAir. (2006). The UltimateAir® RecoupAerator® 200DX Manual and Installation Guide.

Underfloor htaing System. (2010). Hentet fra http://www.underfloorheatingsystems.co.uk/.

Wikipedia. (2010). http://en.wikipedia.org/wiki/Condensing_boiler. Hentet fra Wikipedia.

Wikipedia. (u.d.). Wikipedia. Hentet fra http://en.wikipedia.org/wiki/Thermal_comfort.

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Course materials: Detailed whole-year simulation of a building integrated ventilation concept with heat recovery and night cooling for low-energy buildings. (Christian Anker Hviid, Svend Svendsen) A Guide to Energy Efficient Ventilation, Martin W Liddament (March, 1996)

Lecture 5: Solar shadings Lecture 6: Product development method Lecture 8: Low energy ventilation systems Lecture 14: Combined heating and ventilation Lecture 15: Thermo active building systems Lecture 17: Development of sustainable builædings Lecture 18: Guidelines for design of passive houses and economical optimization Lecture 19_20: Exampples of low energy houses and single family houses Lecture 21: Examples of performances of buildings Lecture 22: Energy supply

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8 Appendix

AppendixA.

Establishingthefunctionsofproductattributes.

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Determinationofengineeringcharacteristics

AppendixB.Condensingboilerdata

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AppendixC.IndoorEnvironment

The summer period is defined from 14th April to 30th September. The winter period is defined from 1st October to 1th April. Even if the environment indoor quality is respected the values related to to the technical rooma re not presented, since the presence of occupancy is 0%. Table 19: temperature range during the winter

Table 20: temperature range during the summer

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Table 21: CO2 concentration

9 IndividualworkWe tried to work at the assignment together so that everyone was involved in each part. We gave the assignment a lot of thought, and think it is better to try to work together as much as possible so that problems can be solved more easily.