3. Chapter three: Research Methodology
3.6. Software
3.6.2. EnergyPlus
EnergyPlus is the most comprehensive building energy simulation program developed by the US Department of Energy, in order to model building heating, cooling, lighting, ventilation and other energy flow, which has been constantly being improved. It is built on BLAST and DOE-2’s most popular features and capabilities, but at the same time, it has many innovative features such as less than an hour simulation time, heat transfer balance-based zone simulation, multi zone air conditioning system, thermal comfort and photo-voltaic systems. EnergyPlus is a simulation program with a user-friendly graphical interface. DesignBuilder has created elegant and easy to use interface to EnergyPlus. (EnergyPlus, DOE, 2018)
3.7. Conclusion
The different climate conditions of Tehran and Berlin will provide a base for similar studies in various climates. By using energy parameters of external envelope for simulations, many different current construction methods and materials in Iran and Germany will not disaffect the results since simulations parameters are not dependent of them. Examining all main directions and minimum to maximum range of window size, will get to inclusive criteria for all possibilities. Considering restricted building energy codes in USA to common available window materials available in Iran, as well as in Germany from current standard and codes to current situation in old buildings, will result in a comprehensive instruction. The energy software that will be used for simulation is DesignBuilder, since incorporates EnergyPlus and has architectural environment and inputs.
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3.7.1. Simulation Parameters of the three sets (Cases)
Case1. Tehran, US Code (IEEC+FNRC)
Window to wall ratio: --- 10, 30, 50, 70, 90 percent Directions: --- East, North, South, West, All directions U-Factor: --- 0.4, 0.6, 0.8, 1.0, 1.2 SHGC: --- 0.4, 0.5, 0.6, 0.7, 0.8
Case2. Tehran, Current
Window to wall ratio: --- 10, 30, 50, 70, 90 percent Directions: --- East, North, South, West, All directions U-Factor: --- 1.5, 2.0, 2.5, 3.0, 3.5, 4.0 SHGC: --- 0.8
Case3. Berlin, ENEV+ Current
Window to wall ratio: --- 10, 30, 50, 70, 90 percent Directions: --- East, North, South, West, All directions U-Factor: --- 1.3, 2.0, 3.0, 4.0 SHGC: --- 0.6, 0.7, 0.8
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3.7.2. Precise description of the simulation models and parameters
Parameters Case1 Tehran, Int. Code
Fixed paramaters Envelope specifications Model size 4x4x3 meter 4x4x3 meter 4x4x3 meter U-value of walls 0.67𝑤𝑤
𝑚𝑚2𝑚𝑚 0.67𝑤𝑤
𝑚𝑚2𝑚𝑚 0.28𝑤𝑤
𝑚𝑚2𝑚𝑚
U-value of roof 0.48𝑚𝑚𝑤𝑤2𝑚𝑚 0.48𝑚𝑚𝑤𝑤2𝑚𝑚 0.20𝑚𝑚𝑤𝑤2𝑚𝑚 U-value of floor 0.45𝑚𝑚𝑤𝑤2𝑚𝑚 0.45𝑚𝑚𝑤𝑤2𝑚𝑚 0.35𝑚𝑚𝑤𝑤2𝑚𝑚
Thermal and visual comfort Heating setpoint temperature
Variable parameters Fenestration Directions East, North, South, West, All directions
Window to wall
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3.8. References:
1. Climate of Tehran, (2013), Tehran yearly weather, < https://weather-and-climate.com/>.
2. Code 19: Energy Conservation in Buildings, Ministry of Roads & Urban Development Iran, (2014), pp. 21-43.
3. DesignBuilder Software Ltd, (2017), Simulation key features,
<https://www.designbuilder.co.uk/>.
4. DesignBuilder Software Ltd, (2017), Simulation Hourly Weather Data,
http://www.designbuilder.co.uk/helpv2/Content/Hourly_Weather_Data.htm 5. Elkins, Dorothy; Elkins, T. H.; Hofmeister, B, (2005), Berlin: The Spatial Structure of a
Divided City, Routledge.
6. Energy Plus, U.S. Department of Energy, (2018), Weather Data,
<https://energyplus.net/weather>
7. EnergyPlus, U.S. Department of Energy, (2018), EnergyPlus Software,
<https://energyplus.net/>
8. EnEV Energieeinsparverordnung, (2016), EnEV online,
<http://www.enev-online.com/enev_praxishilfen/vergleich_enev_2016_enev_2014_neubau_wohnbau_
15.04.06.htm>.
9. Standard Construction Details of Iran, Management and planning organization of Iran, (2010), pp. 34-97.
10. Windows and Glazing, (2016), National Institute of Building Sciences,
<https://www.wbdg.org/resources/windows-and-glazing>
11. World Weather Information Service, (2008), Berlin Climate figures,
<https://worldweather.wmo.int/>
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Chapter 4
Simulation Results and Analysis
Tehran, US Code (IEEC+NFRC)
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4.1. Introduction
In this chapter, the first case of simulations results are presented and analysed.
Then applicable instructions are provided for using by architects and designers.
This case is “Tehran, US Code (IEEC+NFRC)”. It refers to low rise residential buildings in Tehran climate, using Iran’s common construction materials based on the Code 19 (Energy conservation in building) for building’s envelope. According to Code 19, for this case study, R-Value of external building parts have been determined as follow:
walls 1.5, roof 2.1 and floor 2.2 (m^2 k)/w, that are equivalent to maximum U-value of walls 0.67, roof 0.48 and floor 0.45 w/(m^2 k)
Regarding windows, the range of 10% to 90% of net wall area (floor to ceiling) of each main squarely building’s side is studied in this research. For energy related parameters, there is not certain restriction in “Iran’s national buildings regulations” for window’s Parameters. The only apply, is to use window's U-Factor as a part of building envelope for one of the two defined energy calculation method named "Karkardi"
(system performance), that for three class of buildings energy, determines three amount of 2.7, 3.4 and 3.94 as acceptable U-values, but are not obligatory. For SHGC there is not any certain rule. Therefore, for setting numerical range of standard window’s Parameters, we referred to United States energy codes of residential buildings. The U-Factors and Solar Heat Gain Coefficient (SHGC) of fenestration products (windows, doors and skylights) have been determined in accordance with NFRC 100 and NFRC 200 respectively. The United States is classified to eight climate zones. Tehran's climate characteristics is similar to climate zone number 4 of US, that its standard U-Factors and SHGC are 0.35 and 0.40. These numbers are the possible minimum amounts; therefore, the simulation range starts from them upwards.
In this case study, the U-Value ranges from 0.4 to 1.2 (0.4, 0.6, 0.8, 1.0, 1.2) and SHGC from 0.4 to 0.8 (0.4, 0.5, 0.6, 0.7, 0.8).
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4.2. Simulation results and analysis for fixed SHGC
In the first part of this chapter, the influence of both window to wall ratio and window’s U-Value on energy consumption have been studied. Window‘s size ranges from minimum to maximum possible size (10-90 percent) and U-Value ranges from 0.4 to 1.2 following NFRC rates. The building’s energy performance is studied in three outputs of cooling, heating and total consumption. The “total” does not consist of just only cooling and heating, but also artificial lighting and house appliances.
Windows are weak parts of building envelope regarding energy loss, because of their low U-Values. Therefore, in most cases increasing their size means increase in heat transfer through building’s envelope, but since they provide natural light and can help heating spaces in cold times, they would be able to reduce energy consumption of artificial lighting and heating.
In general, and in this series of simulations, required energy for cooling increases by increasing window size and for heating decreases, because of receiving more sun radiant heat through fenestration. Since U-Values of windows are low and extracted from strict codes, they do not have big differences to UV of other parts of envelope, therefore their large size does not result in high amount of heat exchange and energy loss. As an inclusive rule, adding value of thermal transmittance will end to more heat loss and more energy consumption.
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4.2.1. Cooling energy consumption simulation results Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TEHRAN1-NORTH-SHGC 0.4 UV(0.4-1.2)- COOLING
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.2.2. Cooling energy consumption simulation analysis Variable 01---window’s size: 10% - 90%
Variable 02---window’s U-value: 04 - 1.2 Fixed---SHGC: 0.4
Least variation change: The minimum change in energy consumption graphs, can be seen in the north direction, where 127.78 to 211.60 (83.82 kWh)
Most variation change: The maximum change in energy consumption graphs, can be seen in the south direction, where 135.36 to 352.25 (216.89 kWh)
Notable points:
1. In all four main directions there is Incremental linear graph lines, which imply that increasing window size will result in more energy consumption for cooling of internal spaces.
2. Although higher UV has better performance, but graph’s lines are very close together in both angel and measure, and almost are in accordance to each other.
This shows that disadvantage of rising window size on energy consumption is nearly same in all amounts of UV. The reason is that heat gain through windows is done by Radiation Transmission, not conduction.
3. In north direction, graph shows smaller trend to increase. The reason is less amount of sunlight penetration, in this envelope side, and lower heat gain from sun which needs fewer cooling energy.
4. At the graph of “all dir.”, when W/W ratio gets to higher percentages, we see that progressive slope of the graph lines are declined. It is why the simulation model is one-unit space that has window on all four direction walls; In high window percentages, receiving sunlight gets to very high amount and changing window size has lower influence on it.
Instructions:
For cooling internal spaces, the less size of window has better energy performance, to the extent of daylight need. There is not any preference for increasing window to wall percentage.
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4.2.3. Heating energy consumption simulation results Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TEHRAN1-WEST-SHGC 0.4 UV(0.4-1.2)- HEATING
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.2.4. Heating energy consumption simulation analysis Variable 01---window’s size: 10% - 90%
Variable 02---window’s U-value: 04 - 1.2 Fixed---SHGC: 0.4
Least variation change: The minimum change in energy consumption graphs, for three directions of east, west and north are almost same: East 628.38 to 909.05 (280.67 kWh), West: 635.82 to 910.82 (275.00 kWh) and North: 792.09 to 1078.17 (286.08 kWh) Most variation change: The maximum change in energy consumption graphs, can be seen in the South direction, where 233.3 to 830.82 (597.52 kWh)
Notable points:
1. Both east and west directions, have similar trends and graphs which decrease slightly and constantly by w/w ratio increase. Having larger windows let more sunshine inside while their low UV prevents heat loss conductivity.
2. In the north direction, there is two opposite graph trends, rising for higher U-Values and failing for lower U-U-Values. Heat gain in building’s windows in north direction is not as much as east and west. Therefore, only in lower UV there is positive heat exchange through windows which means getting more sun’s warmness than transmitting heat from inside to outside.
3. In south it could be seen that numbers have come down considerably by increasing window size. Obviously, it is much sun light in the south that declines need for heating, in particular using these high-quality windows (low UV) that hinder heat transfer to outside.
4. At the graph of “all dir.”, for lower UV it is dropping while for higher UV it comes down then goes up. Large windows having less thermal resistance, although get more solar heat but let more heat transfer through it to outside.
Instructions:
For heating internal spaces, in all four main directions, it is recommended to increase window size for consuming less heating energy, at all amount of UV. The only exception high UV in the north side and all-dir. that smaller windows performance have better performance.
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4.2.5. Total energy consumption simulation results
Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TEHRAN1-SOUTH-SHGC 0.4 UV(0.4-1.2)- TOTAL
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TEHRAN1-NORTH-SHGC 0.4 UV(0.4-1.2)- TOTAL
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.2.6. Total energy consumption simulation analysis Variable 01---window’s size: 10% - 90%
Variable 02---window’s U-value: 0.4 - 1.2 Fixed---SHGC: 0.4
Least variation change: The minimum change in energy consumption graphs, for two directions of east and west are almost same: East 1283.04 to 1440.61 (157.57 kWh) and West: 1331.78 to 1499.14 (167.36 kWh).
Most variation change: The maximum change in energy consumption graphs, can be seen in the South direction, where 938.34 to 1318.97 (380.63 kWh)
Notable points:
1. Both east and west directions, have similar trends and graphs so that changing UV and window size has not great impact on energy consumption. For higher UV energy consumption rises by making windows larger and for lower UV it reduces, whilst for medium UV of 0.8 by increasing w/w energy consumption remains constant. It means that in this range of UV, the amount of energy loss through windows are almost same to energy got by window in the form of heat and light.
2. In the north direction, the general trade is similar to east and west, but slightly more increase of all graphs. Clearly the reason is less solar radiation in the north and lower energy receive. Windows UV is close to other envelope’s part and having large fenestration does not lead to much heat exchange.
3. In south it could be seen that energy consumption amounts have come down considerably by increasing window size. Obviously, it is much sun light and warmness in the south that declines need for heating. In high window sizes, slope of decreasing graphs gets down, by reason of overheating and need to cooling south spaces.
4. If building has window in all directions, the percentage of 30-40 for w/w has best performance while previous decreasing graphs start to increase upward.
Instructions:
In the main, for reducing total energy consumption it is recommended to provide larger windows in south but for other directions there is not strong preference just for higher UV larger windows, and for lower UV smaller windows have better performance.
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4.3. Simulation results and analysis for fixed U-Value
In the second part of this chapter, the influence of both window to wall ratio and window’s SHGC on energy consumption have been studied. Window‘s size ranges from minimum to maximum possible size (10-90 percent) and SHGC ranges from 0.4 to 0.8 following NFRC rates. The building’s energy performance is studied in three outputs of cooling, heating and total consumption. The “total” does not consist of just only cooling and heating, but also artificial lighting and house appliances.
Windows transfer heat more than other parts of building’s envelope, but sun light penetrates through them to internal spaces. Sun’s warmness coming from fenestration, can help to internal heating or can cause more need to cooling. This received solar heat through windows measured by SHGC which increasing its amount, could have positive and negative impact on energy consumption, regarding direction and size of window.
In general, and in this series of simulations, required energy for cooling increases by increasing window size and for heating decreases for all SHGC amounts, because of receiving more sun radiant heat through fenestration. But for total energy consumption, it is very influential for south direction depending on SHGC, but for next three directions has very little impact. As an inclusive rule, reducing SHGC of fenestration, especially in south, will end reducing energy consumption, because of hot summers of Tehran.
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4.3.1. Cooling energy consumption simulation results Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.3.2. Cooling energy consumption simulation analysis Variables 01---window’s size: 10% - 90%
Variable 02---window’s SHGC: 04 – 0.8 Fixed---U-Value: 0.4
Least variation change: The minimum change in energy consumption graphs, could be seen in north direction, where 128.61 to 377.80 (249.19 kWh).
Most variation change: The maximum change in energy consumption graphs, can be seen in the South direction, where 136.17 to 896.49 (760.32 kWh).
Notable points:
1. In the east and west directions, have similar trends and graphs so that there is a steady increase of energy use by growing both window size and SHGC.
2. In the north direction, the general tendency is similar to east and west, but less growing up of the graphs. The smaller graph gradient is the result of lower solar radiation.
3. Graph lines of the south direction are going up steadily like others but having more upward gradient especially for higher SHGC.
4. For the case of windows in all faces, there is a big demand of energy for cooling of large windows in particular for higher SHGC.
Instructions:
In all cases, lower SHGC IS preferred. Likewise, smaller window size results in less cooling energy consumption but the minimum daylight requirement should be received.
There is a considerable point that efficient performance of windows having low SHGC for cooling, which shows the need for producing such windows (glass) in Iran for using in its hot climates and sunny regions.
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4.3.3. Heating energy consumption simulation results Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.3.4. Heating energy consumption simulation analysis Variable 01---window’s size: 10% - 90%
Variable 02---window’s SHGC: 04 – 0.8 Fixed---U-Value: 0.4
Least variation change: Graphs of three direction of are almost in same state, east 381.79 to 888.59 (506.80 kWh), west 379.14 to 890.11 (510.97 kWh) and north 383.46 to 891.19 (507.73 kWh)
Most variation change: In south direction of building we can see the maximum change in energy consumption graphs, where 78.83 to 803.45 (724.62 kWh).
Notable points:
1. In all four directions and all-dir., by increasing window size and decreasing SHGC the energy consumption drops down.
2. In the all-dir. and partly south direction, for percentages more than 40% of window to wall, there is low or no increment in energy consumption. The reason is the amount of heat loss through larger windows to outside.
3. In contrast to cooling, by windows having higher SHGC have a better performance to lower SHCG in regarding heating.
4. The minimum variation of energy change is higher than previous cases. It means that in east, west, and south, changing size and window’s SHGC could have great impact on energy use and should be considered in design.
Instructions:
In general, windows with more SHGC and larger size lead to less need for internal heating. When there is windows on more than one side, especially in south, growing up windows for more than 40 percent of host wall, has not considerable influence.
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4.3.5. Total energy consumption simulation results Variable 01---window’s size: 10% - 90%
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
TOTAL ENERGY CONSUMPTION (KWH)
WINDOW TO WALL RATIO (%)
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4.3.6. Total energy consumption simulation analysis Variable 01---window’s size: 10% - 90%
Variable 02---window’s SHGC: 04 – 0.8 Fixed---U-Value: 0.4
Least variation change: Graphs of three direction of are almost in same state, east 1277.30 to 1376.31 (99.01 kWh), west 1319.82 to 1414.23 (94.41 kWh) and north 1262.15 to 1351.16 (89.01 kWh)
Most variation change: In south direction of building we can see the maximum change in energy consumption graphs, where 936.10 to 1328.11 (392.01 kWh).
Notable points:
1. In three directions of East, West and North, the variation range is low and by increasing window size and changing SHGC there is not notable difference in total energy consumption, which maintains almost the same level.
2. In south, there is a reverse movement in graphs which first come down and then up, especially for higher SHGC. The reason is over-heating in southern spaces caused by large windows that let more sunlight due to high amount of solar heat gain coefficient and more need for cooling energy demand.
3. In the “all-dir.” Or when there is window in more than one side of space, the upward movement of energy consumption graphs start earlier in smaller window sizes. The main major cause is the increasing cooling energy for larger windows that get more solar heat.
4. In all cases, the position of low and high SHGC graphs invert from small to large windows. Smaller windows have better performance with higher SHGC, while large ones are better when SHGC is lower. The reason comes from their converse position in cooling and heating graphs. Where lower SHGC are
4. In all cases, the position of low and high SHGC graphs invert from small to large windows. Smaller windows have better performance with higher SHGC, while large ones are better when SHGC is lower. The reason comes from their converse position in cooling and heating graphs. Where lower SHGC are