The Council for Scientific and Industrial Research (CSIR) in South Africa is one of the leading scientific and technology research, development and implementation organisations in Africa. It undertakes directed research and development for socio-economic growth.

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Water use in green buildings

Large volumes of water are used in buildings on a daily basis. To enhance the green status of buildings, efforts should be made to develop water systems for water conservation. In South Africa, there is a move towards water-efficient taps and dual-flush toilets in new buildings, but we have much catching-up to do.

The CSIR‘s Dr Jeremy Gibberd comments on water systems for making buildings greener.
While it is very difficult to construct large rainwater tanks and to recycle used water in existing buildings, we should aim to develop water systems to minimise the consumption and pollution of water when designing new buildings.
Water systems in green buildings have a number of characteristics:

  • They can be self sufficient, meeting water needs through rainwater harvesting.
  • Water quality is matched with its use – the best water is, for example, used for drinking, while ‘grey’ water (e.g. from basins and showers) can be used for flushing toilets and irrigation purposes.
  • In natural environments vegetation and soil absorb and retain a large proportion of rain water that falls on to it. Green buildings aim for onsite water retention by permeable surfaces that absorb water and avoid the generation of large quantities of runoff water.
  • Air can be cooled and the humidity increased through evaporation of water and transpiration from plants. This may be used in green buildings to improve comfort levels without the use of mechanical systems.

Some performance objectives for green building water systems


Performance objectives in green buildings

Potable water consumption

Buildings consume 50% less mains potable water compared to conventional buildings

Rainwater harvesting

Buildings meet at least 40% of its water requirements from rainwater harvesting

Hand basin taps

Hand washbasin taps specified have flow rates lower than 6 l/minute


Showerheads specified have flow rates lower than 10 l/minute


Toilets specified have no or low water requirements. Consumption does not exceed 4,5 l for ½ flush and 9 l for a full flush

Storm water runoff

The amount of runoff from a site may not be increased as a result of development. In addition, the quality of the water is not affected negatively.


Planting specified requires little or no irrigation unless planting is for food production

Large water consuming equipment

Equipment and facilities with large water consumption requirements are avoided. If this is not possible, they are made as water efficient as possible by using rainwater harvesting, water recycling and minimising evaporation

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