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athroom combined use at least 80 per cent of total residential water use (see Figure 3.1). 3.32 The Environment Agency report Water Efficiency in the South East of England, Retrofitting existing homes 48 shows that retrofitting existing homes has the potential to save an extra 31 litres/person/ day over the current Building Regulations requirements relatively quickly with existing and simple technology. Three Regions Climate Change Group report Your home in a changing climate 49 identifies and quantifies the options, costs and benefits for retrofitting existing homes to adapt to the impacts from a changing climate including water stress, flooding and overheating. 3.33 A theoretical case study of a typical semidetached house with a family of five, calculated that a full suite of retrofitted Table 3.2 Costs of meeting Code water consumption targets for housing water saving items and appliances, could save up to 109 litres/person/day. The associated hot water savings equated to reductions in energy use of 1430kWh/year, approximately £132 off energy bills and a CO 2 emission saving of 600 kilogrammes/ year. Even a simple retrofitting exercise consisting only of low-flow showers, WCs and taps, delivered water savings of approximately 50 litres/person/day 50 . However, as with new construction (see paragraph 3.29 above) there are still too few large-scale examples to be certain that the anticipated water savings will be achieved in all cases. 3.34 Figure 3.2 illustrates the relationship between water use in the home (centre), overall carbon emissions associated with water supply and wastewater treatment (left), and the carbon emissions from all House type Base cost* Code level 3 and 4 Code level 5 and 6 Additional cost % addition Additional cost % addition Traditional detached house £91,206 £125 0.1% £2,645 2.9% Traditional end terrace house £75,235 £125 0.2% £2,645 3.5% Traditional low rise flat £79,200 £125 0.2% £805 1.0% Traditional high rise flat £124,500 £125 0.1% £805 0.6% ‘Weber Haus’ £59,958 £125 0.2% £2,645 4.4% ‘SixtyK’ house £60,000 £125 0.2% £2,645 4.4% • Base cost is the cost of construction to comply with the 2006 Building Regulations. Code levels 1 and 2 are met within the base cost. Code levels 5 and 6 were met by adding grey water recycling or rainwater harvesting systems to meet 30 per cent of the water requirement. It is worth noting that the Cyril Sweett cost estimate for Code levels 5 and 6 flats are in line with the Tokyo experience (see Case Study on page 55) that water reuse systems add up to 1 per cent to construction costs. These cost do not include land costs, so the cost of meeting the Code standards will be a significantly lower percentage of the overall sale price of new houses and flats. 49
50 The Mayor’s draft water strategy activities in the home (right). The left-hand pie chart shows that water use in the home accounts for 89 per cent of all the carbon emissions resulting from water use. Water abstraction, treatment and supply together with wastewater collection and treatment only accounts for just 11 per cent. 3.35 The right-hand pie chart shows that water use accounts for 27 per cent of carbon emissions from the home. This is made up of 19 per cent from the heating of water for baths, showers, and hand washing and washing up. Water-using appliances including dishwashers and washing machines account for the other nine per cent. Taking a shower rather than a bath – in other words, using less hot water – will therefore only have a relatively small effect on the carbon emissions from water supply but a much bigger effect on carbon emissions from the home. Figure 3.2 Carbon emissions resulting from water supply, use and wastewater treatment Carbon emissions from domestic water supply and wastewater treatment Water supply 0.4% Water abstraction 1/6% Water treatment 2% Wastewater treatment 7% Water in the home 89% Carbon emissions from water use in the home WC 7% Basin 11% Bath 14% Kitchen sink 21% Shower 12% Washing machine 16% Dishwasher 19% Sources: Environment Agency 51 (left chart) Energy Saving Trust (centre chart) Carbon emissions from all energy use in the home Other appliances 9% Cooking 3% Water-using appliances 9% Hot water 18% Lighting 5% Space heating and cooling 54%
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