Four factors to consider when designing a green building

Two weeks ago, we looked at the first five points in the UN-Habitat charter for sustainable building design in tropical countries. Today we look at four more guidelines.

1. Window openings: The size of windows should be designed according to prevailing climatic conditions.

Preferably, they should also be placed along the North/South facing walls where they will have minimal exposure to direct heat from the sun while at the same time letting in enough light. The window to wall ratio should not be more than 40 per cent.

2. Daylighting and solar protection: If you live in a house where you have to use artificial lighting during the day, then the design is already compromised. A narrow house design allows much light from the sun to penetrate through.

Home services such as staircases, toilets and the kitchen should be placed on the East/West facing walls where they will be well-lit and at the same time absorbing much of the heat that would otherwise get into the main areas of the house.

It is crucial to use roof overhangs, vertical or horizontal shading fins, window screens and even vegetation to keep out the heat from the building.

3. Ventilation, heating and cooling: A well-ventilated house is pleasant to live and work in. Sadly, many buildings rely on mechanical elements for ventilation purposes.

Apart from running high power bills, such devices may contribute to emission of greenhouse gases to the environment.

Solar

Cross and vertical ventilation is possible through roof vents and thermal chimneys. Water features in the compound also aid in evaporative cooling in hot and arid regions. On the other hand, buildings in highland areas require passive solar heating strategies.

4. Building envelope and materials: A developer should always consider a building’s footprint to ensure minimal interference with prevailing environment. Locally available building materials are preferable due to their low energy content. It should also be possible to recycle and reuse material due to their low toxic content.