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