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Sustainability is at the core of the Three Gardens affordable housing project in Suffolk. 鈥淭he scheme has very low in-use and embodied carbon emissions compared with almost any other UK residential project,鈥� says Alasdair Young, project leader from Buro Happold鈥檚 sustainable and alternative technologies team.

The 26-home scheme at Elmswell was commissioned by Orwell Housing Association and Suffolk Preservation Society in response to a lack of affordable housing for local people in an area rapidly growing as a commuter belt. It has 13 two-bed and nine three-bed houses plus four one-bed flats, arranged to maximise passive solar gain and daylight in winter as well as minimising overshadowing.

鈥淭he building envelope and glazing ratios were modelled by Buro Happold to establish the optimum relationship between solar gain and daylight penetration,鈥� explains Young.

The houses are timber-frame construction, with the walls fabricated from hemcrete sprayed onto the wooden formwork. Hemcrete is a hemp and lime mixture that has excellent environmental and thermal properties. Hemp is one of the region鈥檚 oldest crops. Young says it has the ability to lock carbon into the fabric of the building because it absorbs more carbon while growing than is used in its subsequent manufacture. The scheme鈥檚 environmental credentials were enhanced further through the use of local sheep鈥檚 wool insulation.

Energy efficiency is helped by whole-house ventilation with heat recovery, improved air-tightness and highly insulated walls. These measures and a biomass-fired community heating system, using locally sourced fuel, are designed to reduce the scheme鈥檚 carbon emissions by about 60% compared with a standard regulations-compliant scheme.

Water is another resource the scheme aims to conserve. Rainwater will be collected in underground tanks for flushing toilets and watering gardens, while swales (open, marshy drains) will deal with run-off water.

As well as providing drainage, these will separate the pathways, play and planted areas, mimicking the pattern of ploughed fields. The four communal green spaces, also open to non-residents, are a wildflower meadow, an apple orchard, an allotment and a playing field.

Construction is under way. 鈥淭hree Gardens aims to achieve an Ecohomes excellent rating as well as being a first-rate example of cost-effective, sustainable design,鈥� says Young.