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Simulation Results

According to the simulation results for the base model,  it is observed that there is both heating demand in the winter and cooling demand in the summer with the majority of the demand being from the cooling. It was also noticed that both the first and forth floor had the highest demand for the heating, this was mainly because they have a large area exposed to the external environment being the roof and the floor. This could be address by altering the thermal resistance using insulation which is seen in the next diagram.

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Insulation

Insulation refers to an energy savings measure, which provides resistance to heat flow. Naturally, heat flows from a warmer to a cooler space. By insulating a house, one can reduce the heat loss in buildings in cold weather or climate, and reduce the heat surplus in warmer weather or climate.

Insulation Analysis
In analyzing the thermal behavior of walls, different levels of
thermal resistance was achieved by adding extruded polystyrene
(EPS) thermal insulation to the roof, ground floor and external walls of the Base case commercial building. The thickness of EPS was increased in steps to decrease the U-Value each time by half as shown in the chart below.

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It can be seen from the above diagram, the highest decrease was due to the roof and the ground floor insulation. The external walls insulation had minimum effect on the heating load. The U-value that was selected was far from the one suggested by ASHRAE  for this climate zone as the difference in saving is very low. This shows that when using the standards for building insulation you will be on the safe side but when modeling the building you will be saving more than ten times the cost of insulation in this building.

The below illustration demonstrates firstly the decrease in heating demand after the roof and floor were insulated, then the decrease that resulted with different wall insulations compared to the demand after the roof and floor were insulated.

Roof & Floor

U 0.65

U 0.33

U 0.15

U 0.09

Although the heating demand decreases with more insulation, the cooling load increases because more heat is being trapped in the building as shown in the chart and graph below.

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After the heating demand was reduced, the cooling demand was to be addressed. A high cooling load could be as a result of two main factors, internal gains and solar radiation entering the building. 

As it can be seen from the graph below  that the solar radiation entering the building is high which results in higher cooling load. This is due to the large area of the windows and glazing facades which allow excessive solar radiation to enter the building, for instance the first floor glazing area constitutes about 40% of the exterior.  Based on this result, measures to decrease the solar gain were then investigated. 

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Shading

The use of sun control and shading devices is an important aspect of many energy-efficient building design strategies. In particular, buildings that employ passive solar heating or daylighting often depend on well-designed sun control and shading devices.

During cooling seasons, external window shading is an excellent way to prevent unwanted solar heat gain from entering a conditioned space. Shading can be provided by natural landscaping or by building elements such as awnings, overhangs, and trellises. Some shading devices can also function as reflectors, called light shelves, which bounce natural light for daylighting deep into building interiors. [1]

The design of effective shading devices will depend on the solar orientation of a particular building facade. For example, simple fixed overhangs are very effective at shading south-facing windows in the summer when sun angles are high. However, the same horizontal device is ineffective at blocking low afternoon sun from entering west-facing windows during peak heat gain periods in the summer.

Exterior shading devices are particularly effective in conjunction with clear glass facades. However, high-performance glazings are now available that have very low shading coefficients (SC). When specified, these new glass products reduce the need for exterior shading devices.

To decrease the amount of solar radiation the first measure that was investigated was using shading on the south facing windows and glass facades to block a large portion of the high summer sun in the summer, this has decreased the amount of solar radiation entering the building significantly as can be seen in the graph below.

29 

Cooling Demand Reduction (%)

48

Heating Demand Increase (%)

23

Total Annual Energy Saving (%) 

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Solar Control Glass

In hot climates, solar control glass can be used to minimise solar heat gain and help control glare. In temperate regions, it can be used to balance solar control with high levels of natural light.

The second measure that was investigated to decrease the solar radiation entering the building is glazing system. Glazing system in the base model was replaced by a different glazing type for windows and facade. The new glazing type used was low-emissivity film coated double-glazing, 6mm plate glass with 12mm air gap and U-value of 2.5 W/m²K.

This type of glazing is primarily used in commercial buildings, either for façades, windows or overhead glazing. The level of transmitted light is as high as 65% and often ideal in case of largely glazed curtain walls or skylights. The level of visible reflection reinforces the perception of transparency and allows for undisturbed views from outside the building into the interior.

Although the level of natural light is still high the solar heat gain is extremely low with a g-value as low as 0.33!
In other words: 67% of solar energy radiation does not enter the building, but is rejected!
The very low solar factor; reduces cooling loads therefore reduces the cost of air conditioning is more environmentally friendly, as it reduces the use of primary energy and associated CO2 emissions.

As it can be seen from the graph below that there is a further significant decrease in the solar gain entering the building

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As it is shown on the chart to the left, the cooling demand has decreased by almost a third. Although the heating demand has increased but there was a total annual energy reduction of 17.5%.

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Internal Blinds

Blinds are used to control the solar radiation entering through the windows and can be very effective in hot climates.

Lastly when addressing the solar gain the effect of placing blinds was investigated. Although there was a large decrease in the total demand, fitting blinds will sacrifice the view of the windows so it was decided to use the above glazing rather than the blinds .

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High Efficiency Lighting

Lighting is an important issue in minimizing overall energy consumption . For the industrialized countries, lighting accounts for 5–15% of the total electric energy consumption. Besides direct savings, indirect energy savings can be realized due to a reduced consumption for air conditioning.[2]
In commercial buildings, it normally accounts for more than 30% of the total electrical energy consumed.  Yet much of this expense can be avoided.[3]

After the measures to decrease the solar gain were in place, the measure to decrease the internal gains was investigated. One of the major sources of internal heat gain would be the lighting.
In the base case, typical fluorescent lighting was used, then replaced by high efficiency LED lighting which resulted in both a decrease in the energy used by the lighting and the cooling demand. this resulted in a reduction of 23% in cooling demand and a total reduction of 7%.

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Color of External Walls & Roof

Solar absorption through the roof and walls contributes to the heat gain of the building, and by painting the building in a light color with a low solar absorption coefficient, most of the solar radiation would be reflected. According to a study in Greece light-colored walls and roof reduced the space cooling load by 2-4%.[4]

It can be seen from the chart below that after changing the color of the roof and walls to white with a solar absorption factor of 0.22 , there was a decrease of 4% in the space cooling demand and the total saving was 2.6%.

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The diagram below summarizes the measures that were used to achieve this reduction in both heating and cooling demand. The demand is represented in kWh per meter square per year to give an understanding of how much energy is used to condition each meter square of the building per year. To convert the cooling demand into energy demand, a COP of 3 was assumed and this was to represent an air source heat pump. A detailed calculation of the hourly COP at different temperatures was not carried out due to the time constrain of this project but a qualitative assesment of the possible solutions was carried out. 

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According to a study in Istanbul, the ground temperature at 6m below the ground is about 16°C all year round, which would make ground-source refrigeration very relevant and much more efficient compared to air-source refrigeration[5]. Ultimataly, at this temperature, water could be pumped for floor cooling without the need for a heat pump.

The chart below shows the annual total demand of the building after each measure was applied. Starting with the demand profile of the base case (79.56 kWh/m²) passing through the other measures and ending with the final demand profile after the last measure (using efficient lighting) was applied (55.43 kWh/m²).

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The below chart illustrates the difference between using a heat pump with a COP of 3 and a high efficiency gas boiler for the heating demand.  

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The graphs below show the building behavior at different seasons and it shows that the dry bulb temperature remains within comfort range between 24°C and 22°C.

[1] Prowler, D. (2016). Sun Control and Shading Devices | WBDG Whole Building Design Guide.

[2] Ryckaert, W.R., Lootens, C., Geldof, J. and Hanselaer, P., 2010. Criteria for energy efficient lighting in buildings. Energy and buildings, 42(3), pp.341-347.

[3] Wbdg.org. (2016). Energy Efficient Lighting | WBDG Whole Building Design Guide.

[4] Balaras, C.A., Droutsa, K., Argiriou, A.A. and Asimakopoulos, D.N., 2000. Potential for energy conservation in apartment buildings. Energy and buildings, 31(2), pp.143-154.

[5] Aydin, Murat & Sisman, Altug & Gültekin, Ahmet & Dehghan B., Babak. (2015). Experimental and computational performance comparison between different shallow ground heat exchangers. 

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