On a hot Tuesday, I sat in a conference room for nearly nine hours but the whole time, all the occupants of the room did not feel the need to either switch on the wall fans or the lights because the lighting and cooling in the room were sufficient.
According to an architect who was part of the conference, the room was about 7 by 14 feet but it was fitted with six windows to the left (slightly to the north), two to the right (slightly to the south) and two doors on the same side.
Dr Vincent Kitio, the chief Urban Energy Unit Urban Basic Services Branch, UN-Habitat says the features of this building are strategies of green building. He explains.
“Green building also referred to as sustainable building design is a shelter that protects you from the negative effects of weather and preserves the environment at the same time.”
Kitio says such a building looks at the environment, landscape, economics and the local context of the area among other features.
One of the advantages of sustainable building design is that it consumes less resource. Dr Kitio explains, “Setting up a green building might be a little expensive at the beginning but cheap in the long run because it is long-lasting and has less impact on the environment.”
Architect Musau Kimeu, an environment design expert and an acoustics specialist in Nairobi, Kenya explains that to achieve green building, UN Habitat developed a charter for sustainable building design.
It consists of a set of building strategies, which are explained below.
STRATEGIES TO REALISE GREEN BUILDING
1. Positioning of the building
Architect Kimeu explains that orientation (positioning) of the building is one of the strategies of sustainable building design.
He says, “Make sure that the windows do not face either the east or west because this is the direction of the sun. The south and north are ideal.”
Dr Kitio explains the significancy of windows and doors facing the east and west, “When the sun rises in the morning, the heat will go through these openings into the house and keep it hot throughout the day and the same will happen when it sets in the evening thus keeping the house hot throughout the night.”
2. Location of rooms
Kimeu says, “You need to bear in mind location of rooms. Having a living room or bedroom facing west or east is not a good idea in East Africa because we have a hot climate. But if your rooms or openings are facing this direction, especially because of the shape of your land, you need a canopy (covering) such as an extended slab or roof to shield them from direct sun.”
He adds, “Locate building services such as toilets, stair case and all inhabitable spaces to the east and the west; these will be used as buffers to the sun.”
3. Long and narrow buildings
You should have buildings that are narrow and long as opposed to wide or round rooms because ventilation in such rooms becomes a challenge and so it needs artificial cooling, which will increase your expenses.
Additionally, the Urban Energy Technical notes on green building read in part, “Buildings that are narrow in plan help to achieve maximum natural lighting penetration, good cross ventilation and minimise heat gain.”
4. Sun shading
Sun-shading of all glass areas is another strategy of sustainable buildings design. Kimeu explains that to achieve this, you need to build an extended roof or slab over all glass areas of the house to prevent the effects of direct sunlight.
“It is the most important point when building in hot areas because glass allows short wave radiation which goes through glass so any heat that gets in through glass continues to build up which is why you will need artificial air conditioning.”
5. Size of windows
Window sizing should be according to the prevailing climate conditions and Uganda being in the tropics or hot and humid area, Dr Kitio advises that the windows should not exceed 30 per cent of the wall. “This will help in preventing heat gain in the house, which comes with using a lot of glass.”
For a tropical climate, it is recommended that you have your buildings smooth on the surface and light-coloured to reflect heat. “The colour of the building also matters that is why we advocate for light colours which reflect heat such as white mainly for the interior. Dark colours absorb light and heat so you tend to use more light and artificial cooling.”
7. Size of walls
“All external walls should be at least 200mm thick to prevent heat from penetrating through. This keeps the heat away for a long time so the interiors remain cool.”
8. Choice of building materials
Use local materials as opposed to imported materials. These have none or minimal maintenance, they can easily be harvested and are non-toxic so they have minimal internal pollution and damage to health and are also easy to recycle or to reuse.
9. Power source
It is recommended that you use renewable energy through solar power harvesting.
10. Water efficiency
You need to use water- saving fixtures such as dual flush systems and low flow taps. Instead of letting rain water to flow, you should harvest it and use it for various purposes such as watering plants and for cleaning. “This will reduce the pressure of using the piped water which is causing water levels to go down.”
This calls for the need to have environment friendly toilets such as bio digesters, reed bed sewerage systems and oxidation ponds.
12. Waste management
Waste needs to be sorted out at the source and the biodegradable waste used to produce biogas is separated from the non-biodegradable waste which is recycled.
When landscaping, use local plants because these require minimal watering and manure instead of fertilisers, which is a chemical that will affect the soil structure and have long-term side effects.
Dr Kitio adds, “It is also important that you use permeable or porous paving material to allow water to penetrate the ground. This will raise the water table.”