Water benefits The water efficiency of green buildings translates into cost savings for the supply of potable water. A variety of water-efficiency strategies is being pursued particularly by countries facing water stress and water scarcity. In India, innovation in indigenous and green building approaches include rainwater harvesting with segregation of surface and roof-top run-off, the use of pervious paving to maximise groundwater recharge, as well as the introduction of waterless urinals (UNEP SBCI 2010a). In Mexico, a Green Mortgages programme of the public fund, INFONAVIT, provides credit for water and energy-conservation measures, including the introduction of solar water heating and low-flow showers (UNEP SBCI 2009b). In New South Wales, Australia, the government-owned land and property developer, Landcom, has defined principles such as water sensitive design, which have to be met by suppliers. It has promoted building-sustainability indicators, introduced by state regulation and requiring 40 per cent improvement in GHG emissions and water management in all new housing (Martinez-Fernandez et al. 2010). In Melbourne, City Council House II has achieved a 72 per cent reduction in mains water usage through a combination of water efficiency, rainwater harvesting, water recycling and sewer mining (von Weizsäcker et al. 2009).
Further, demand-side management of household water-use covers appliances used for toilets, urinals, showerheads, taps, washing machines and dishwashers. Using water efficient appliances in the home can result
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in significant water savings. For example, modern water efficient dishwashers and toilets can use as much as a 50 per cent less water than less efficient older models or even 100 per cent less in the case of waterless toilets and urinals (Waterwise 2011a and 2011b).
According to Kats (2010), the net present value of 20 years of water savings in a typical green building in the USA range from US$ 5.4 to US$ 21.5 per square metre.18 He further suggests that these direct savings in green buildings outweigh the initial costs of water-efficiency strategies such as rainwater harvesting, waterless urinals and the use of grey water for all building types. A specific example is provided in Box 4. Reducing hot- water usage also brings benefits by reducing water and energy costs for households, businesses, institutions and water utilities.
Waste and material benefits The building sector can be called the industry of “thirds”: over a third of all CO2
emissions come from building
construction and operations, over a third of all energy and material resources is used to build and operate buildings, and over a third of total waste results from construction and demolition activities. Considering efficiency in use of land and materials, green building presents an opportunity to address growing scarcity issues that many societies face owing to the unsustainable use of ecosystem services. It also presents an opportunity to address other environmental and health problems such
18. Original text indicates a range from US$ 0.50 to US$ 2 per square foot.