1.0 THERMAL ANALYSIS

1.1 INTRODUCTION

The aims of thermal analysis are:

To design the building to be naturally ventilated in the summer and thus to minimise the need for mechanical ventilation.
To minimise the heat loss of the building in winter by improving the fabric.
To summarise ideas for heating and ventilating this building in the most comfortable and energy efficient manners.

VARIABLES

Glass types
Different glass types have been taken into consideration.

6/12/6mm clear low Emissivity double glazing units
6/12/6mm solar Antisun Green low E double-glazing units.
10/12/10mm clear low Emissivity double-glazing units.
6/12/6mm solar High Performance low E double-glazing units.
6/12/6mm solar High Performance low E argon filled double-glazing units.

Insulation

Base models are based on architect’s specification of 40mm in thickness, generating a U value of .35W/m2.k. Extra insulation option of about 80mm is taken into consideration too.

Zones

The building is divided into modular zones, which might represent a whole room or part of a room. (Refer to appendix A - Zoning)

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Weather condition
According to the weather database file UK_Kew67_TRY.wfl (Typical Representative Year - gathered in 1967), day 198 (17th July) recorded the peak summer temperature at 28.8oC. And as for winter, day 345 (15th December) recorded the lowest temperature at -3oC. (Refer to Appendix A - Weather Data - for sample weather days)

Air temperature
Is the temperature recorded by the thermostat.

Mean radiant temperature
Is the radiated temperature from different surfaces (glass, light, computers, etc).

Resultant temperature
Is the mean of air and radiant temperatures.

Openings to outside
The base model has no openings and that is to study the effect of radiant heatr on the internal temperatures, also in the case of leaving the house unoccupied for some time. Typlical vents are added as to architects modelling.

1.2 HEATING AND VENTILATION STRATEGIES

1.2.1 SUN PATH
The sun path diagram indicates the position of the sun relative to the building for both winter and summer times.

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1.2.2 SOLAR GAIN
Due to the amount of glass in the building facia, and by examining the sun path and simulation results, it is noted that the building is getting some solar gain all year long. This gain could be usefully used in the winter times, but also need to be treated in the summer times when the global solar radiation is at its extreme.This gain can be treated in different ways, either by: 1 Using solar treated glass, or 2 Hanging internal blinds, or 3 Installing external shading.

1.2.3 WINTER ANALYSIS
The main objective is:
The effect of glazing
The effect of wall insulation

The effect of glazing types
A comparison is made between 6/12/6mm and 10/12/10mm clear low E glass (scenarios 1 & 6), and the results show no major difference in heat loss. Generally there is only 1% improvement.

Another comparison is made between clear glass and solar treated high performance neutral glass, air and argon filled, (scenarios 7 & 8) to study the overall performance of each glass and the amount of heat loss, and the results show that during day hours the clear glass makes the internal temperatures warmer than the solar treated ones and that is due to more solar gain. But the improved high performance solar glass requires lesser energy to maintain room temperatures, and also it withholds more heat in a whole day period. The argon fill has the best performance.

Nevertheless, we logically conclude that in the case of having external blinds, and to get most solar gain, it is preferable to have them open during day hours.

The effect of wall insulation
Because of the dominance of glass on the overall wall formation of the building, we note from the results (scenarios 1 & 9) that increasing the wall insulation will reduce the overall heating load of the building by only 1%, but more importantly, temperatures on the north facing rooms will be more stable.

1.2.4 SUMMER ANALYSIS
The main objectives are:
The effect of glass types
The effect of blinds
The effect of vents

The effect of glass types
Sunrays will penetrate the facade of the building for most of the day hours, and therefore the radiant heat will have a major impact on the internal comfort temperatures. For the base model, clear double glazing units are considered, and they are compared with solar treated double glazing units on the south facia of bedrooms and study room, (scenarios 2 & 3) and the simulation results show that temperatures in the south corridors will drop dramatically from about 40oC to 35oC, an improvement of 5-10 %, and this by itself will improve the temperatures in the rooms generally. (See results sheet).Also a one-day study is made for solar high performance glass for all facia (bedrooms and living), and we note a major impact on the overall day temperatures. (See graphs)

The effect of blinds
The internal blinds have more or less the same impact as the solar treated glass, but the only difference is that the solar gain will be trapped between the glass and the blinds instead of being reflected (scenario 4). They make an improvement of about 6-10% in general internal conditions.Where with the external blinds, very little solar gain will penetrate into the building, and most of it will be reflected back (scenario 5). An improvement to about 20% (see graph)

The effect of vents
By opening the vents, temperatures will drop down dramatically, and that is to the natural fact of offsetting the internal high temperatures by creating the air movement. (Scenario 2) By examining the simulation results, the vents sizes and locations seem sufficient.

As for the living area, and in the case of having external blinds, a comparison is made to examine the effect of high and low level vents (scenarios L1, L2, L3 & L4), and the results show that the best comfort criteria is when both level are open.

An option is taken into consideration, and that is to put the high level vents at roof level (scenario L5), and we note that it keeps the low level living area to its normal but reduces the temperatures at high level.

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THE EFFECT OF SOLAR GLASS

WINTER TEMPERATURES

1.3.1 WINTER PERFORMANCE

• When the occupied areas are typically conditioned, temperatures shall maintain a stable differential between 19 & 20^oC.

• Areas next to large glass façade, i.e. study & bedrooms corridors shall require greater heating load per area than other parts due to greater heating loss.

• Thicker glass (10/12/10mm clear instead of 6/12/6mm) has little impact on the overall heating load and temperatures.

• Using solar treated glass will prevent the amount of solar gain compared to a normal
  clear glass.

• By using argon filled high performance glass, heating loads shall be cut by an extra 7%.

• Expanding insulation thickness shall reduce the heating loads by up to 5% only in the areas where fabric walls dominate.

• To maximise solar gain, external shading should not restrict the sun path to the glazing at day hours.

1.3.2 SUMMER PERFORMANCE

• The building can be naturally ventilated providing it has enough openings to the outside.

• Because of the shape of the building and amount of glazing, the building does get solar gain all day and throughout the year.

• When no action is taken (i.e. clear glass, no vents, no shading), temperatures shall be at there extremes to about 50^oC.

• By using medium performance solar glass to south facade, it makes an improvement of about 6-10% in internal comfort temperatures in the areas next to the glass, and that by itself improves the temperatures in the entire rooms by 5%.

• By simultaneously opening vents to architects specifications, there is enough air travelling through the building to offset the high radiant temperatures.

• In the living area, L/L large vents are enough to move air through the area (temperatures could reach 32^oC). And the H/L small ones could be vital to create extra air movement. By opening only the H/L ones, temperatures could reach 33^oC.
  It is advisable to open the vents at opposite sides (kitchen & living) to generate the essential airflow regardless of wind direction.

• In the living area, positioning the H/L vents at roof level shall have no impact on low levels, but shall help to extract any trapped hot air to outside.

• In the kitchen area, the external blinds make an improvement of about 0.5oC in the afternoon. It is highly recommended to have a form of shading (internal or external) on the kitchen side to prevent the uncomfortable circumstances at early hours of the day.

• In the study and bedrooms, hanging internal blinds to clear glass or just using solar glass will have the same impact, and that is reducing the temperatures to up to 10%.
  External shading shall have the best influence and that is an extra 10%.

• Generally, we highly recommend using solar glass or having external shading to clear glass on the south façade of study and bedrooms, and to kitchen and living low-level elevations.

2.0 THE STANDARD ASSESSMENT PROCEDURES (SAP)

Without putting the full SAP worksheet (Version-9.53) into a .jpg file, the result of this exercise gives us a rating of 103.04. To translate this into language that most of us comprehend, it means that our annual gas bill is likely to be about £532 for a house in which 60% of the vertical surface is glass. Exceeding 100 is rare and demonstrates the thermal integrity of the design.

3.0 LIGHTING ANALYSIS IMAGES