A house or a building can be thought of as being an envelope, which shelters an indoor space from the weather outside. The objective of the envelope is to maintain a comfortable inside environment. One approach is to build the building and then force the inside temperature to be comfortable by using fans, heaters, air conditioners, window louvers or computerised control schemes.
A better way is to design the building with more consideration for its environment so that the need for active space heating or cooling by mechanical or electrical means is substantially reduced, if not totally eliminated.
The principles applied in climate-sensitive design are based on the idea of using natural conditions to the best advantage. The principles of orientation, heat storage and cooling can be combined with specific building materials to achieve climate sensitive design. Energy efficient housing design principles encompasses all the available techniques of creating a ‘healthy’ interaction between indoor and outdoor climate conditions in buildings.
This would include the use of solar passive design strategies to build houses more energy efficient and simultaneously increase thermal comfort in the houses, but also water conservation, use of renewable energies, greening activities and the use of energy efficient stoves.
Solar passive design principles include design and orientation of the house, and the building material used (that is mass, glazing, insulation, use of daylight, ventilation and other systems which might be required).
The sun rises daily in the east and sets in the west. In summer in South Africa, it will pass almost directly over-head at noon, whilst in winter its path will be low in the northern sky. This is true for any location south of the equator, and the further south you go, the lower the sun will be in the northern sky – north of the equator the sun follows a path that is low in the southern sky. Therefore, to let the sun inside the house in winter, most windows should be on the northern side. Windows on the east and west tend to lose more heat than they gain in winter and they can cause overheating in summer since they receive hot morning and afternoon sun. A roof overhang over northern windows shades the windows in summer while allowing sunshine in during winter, due to the lower position of the sun in the sky – the sun shines in under the overhang to heat the inside of the house.
Some practical advise….
* The longer side of the house should be orientated east-west so that it faces north to ensure that the house receives the maximum amount of sunlight throughout the day. Internal rooms should be planned in such a way that the most frequently used rooms, such as the lounge are situated on the north side of the house;
* The largest windows of the house should be fitted on the northern side;
* The roof overhang on the northern side of the house should be calculated to be at an altitude angle equal to 90! Minus latitude, as measured at the windowsill.
When it is not possible to make this calculation precisely, a good guideline to follow is that the overhang on the northern side of the house should at least be 400mm to 600mm in length;
* A roof overhang should ideally be combined with a strip of grass or vegetation to prevent the surface from warming up.
If the sun is allowed to stream in through a window, the room will warm up.