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close this bookDesign Handbook on Passive Solar Heating and Natural Cooling (HABITAT, 1990, 162 p.)
close this folderVII. Detail design
View the documentA. General
View the documentB. Solar access, shading and window protection
View the documentC. Control of conductive heat flow
View the documentD. Evaluation of internal heat loads
View the documentE. Cross-ventilation and air flow
View the documentF. Glass-mass relationship
View the documentG. Air infiltration

D. Evaluation of internal heat loads

The total energy used in dwellings throughout Australia varies largely because of climatic differences. The use pattern for a typical four-person household in Sydney is illustrated In figure 92 while data for other localities can be found in the annexes.


Figure 92. Energy used within the home - Sydney (kWh per annum)

In an energy-efficient building the heat generated inside by the occupants and appliances or equipment in use will compensate for some of the heat lost through the outer fabric. In some of the "super-insulated" houses built in northern Europe and North America, the casual internal heat gain is sufficient to counter the structural heat losses. Very little auxiliary heat is Fresh air is passed through an air-to-air heat exchanger to retain even the heat in the exhaust air.

Table 15. Daily profile of internal heat input from the activities of a tour- person household d. ("Time' is the starting time for the Indicated load, which applies for one hour.)

Time

Living zone
(Wh)

Bed zone
(Wh)

Service zone
(Wh)

Total

Comment

0000

75

225


300


0100

75

225


300


0200

75

225


300


0300

75

225


300


0400

75

225


300


0500

75

225


300


0000

75

225


300


0700

400

450

800

1650

Breakfast,showers etc.

0800

325


325

650


0900

100


200

300

Early morning cleaning

1000

150



150


1100

150



150


1200

225



225


1300

150



150


1400

150



150


1500

150



1500


1600

800

200


1000

Children home: cooking

1700

1200

200


1400


1800

800

100


900


1900

800

100


900


2000

800

100


900


2100

800

100

100

1000


2200

500

150

650


Bed time

2300

75

225


300


Total (Wh)

8100

3400

1225

12725


The magnitude and source of casual internal heat gains will vary from one situation to another. Cultural differences in lifestyle will also impact on energy use. In a typical Australian household the casual internal heat gains can be assumed to be in the order of 8kWh/day in the living zone of a three bedroom-dwelling, with a peak around the time of the evening meal. In mild climates this reduces auxiliary heating for energy-efficient houses. As the stove is the largest single heat source (other than auxiliary space heaters) in the living area, its pattern of use is a key factor in this picture.

The knowledge of internal heat gains is important when determining the thermal behaviour and auxiliary heating and cooling loads of a specific design. Most computer programs require an hour by hour estimate of internal heat gains. Table 15 illustrates the internal heat gains assumed for a typical family home being assessed in the 5-star design rating system, during colder months. Where the maximum outdoor temperature exceeds 27°C the profile should be reduced progressively from 81 00Wh/day to 6670Wh/day when the outdoor maximum is 33°C and above. The reduction should be made to the evening end of the day to reflect the reduced cooking load in warmer weather. The occupancy pattern of the two zones of the building is reflected clearly in the times of significant heat gain.

A table of energy use for a wide range of equipment and domestic appliances is included in annex IV. It must be noted that the main difficulty is to estimate realistic use patterns for these appliances. In many simple evaluations the inclusion of minor appliances is an unnecessary complication.