When neighbouring houses were built by Countryside Homes for several housing associations some 10 years ago, the site for the two three-bed semis now completed at Eider Close in Newham, London, was an electricity substation. Since then decommissioned, the small site provided East Thames Housing Association with a chance to try something different.
The association is committed to exploring and developing a sustainability agenda in the longer term, within the normal cost constraints of Housing Corporation Funding. For this project, some extra costs were deliberately incurred to seize the opportunity of the site as a test bed for the viability of a range of predominantly energy-saving measures.
Scheme design and subsequent monitoring are the responsibility of PRP Architects.
Detailed design was passed to ECD Architects, which worked to a large extent within the framework of BRE's EcoHomes assessment scheme. The scheme embraces:
lenergy - CO 2production, envelope performance, exterior clothes-drying space, eco-labelled white goods (not done here), low-energy security lighting;
ltransport - access to public transport and local amenities, cycle storage (not done here), home office potential;
lpollution - avoiding CFCs/HCFCs and limiting NOx emissions;
lmaterials - timber for fabric and finishes, recyclable materials, materials' environmental impact (Green Guide for Homes);
lwater - low consumption;
lland use and ecological value - ecological value of site and change in that, building footprint; and lhealth and well-being - daylighting, sound insulation, private outdoor space.
While conventionally planned, PRP has included some exterior untreated larch boarding to signal the fact the house is timber-framed, though its area was limited by the client's concerns about maintenance costs (which should be minimal) and impact damage. Envelope U-values are about 15 per cent better than Part L1. Window areas are larger on the south elevation for solar heat/light input and amenity. A sedum roof has been a talking point in the neighbourhood, the summer flowering awaited.With a conventional roof pitch, roof watering should not be needed in summer.
Two particular technologies introduced are solar panels for pre-heating hot water in one of the houses, and grey water recycling for flushing WCs in the other. (Cost constraints prevented both systems being put in both houses. ) The solar collector works via a coil in a larger-than-normal storage tank, which also has a coil from the boiler. The southerly-facing 4m 2selectively coated flat plate collector is expected to provide 50 per cent of family water needs year-round. Since occupation in late April, top-up from the gas boiler has not been required. Details needed developing with the sedum roof manufacturer to deal with fixing the collector. (There were also discussions - too late - about detailing other roof penetrations that would have allowed trialling of a Passivent passive stack ventilation system to kitchen, bathroom and WC. A fan-assisted version has been installed. ) The grey water system collects water from baths, hand basins and showers, then filters and disinfects it in a tank under the patio, and pumps it to a header tank for use in flushing WCs. The header tank drains after 48 hours if not used. It is a self-cleaning system incorporating slow-release bromine tablets.
As well as energy modelling, other measures included Hep2O push-fit plumbing rather than copper, newsprint insulation, recycled materials in manufacturing dpcs, improved party-wall sound insulation, waste segregation and porous external paving (to avoid drainage to sewers). Paints are water based - the association might try earth-pigmented paint in future. Dedicated car parking is at a standard 1.5 spaces per house. The houses also conform to Lifetime Homes standards.
The two major systems - solar and grey water - demand little of occupants beyond accepting being part of a trial. (The slowerresponse nature of passive ventilation might have required more change of behaviour. ) This is a small trial, and individual energy consumption is notoriously variable, but PRP has sought some comparability by obtaining bills from the occupants' time in their previous home. During the next year bills will be monitored for gas, electricity and water.
Cost-wise, such grey water systems require an initial investment of between £1,400 and £1,800 each, which could produce a saving in the order of 30 per cent in water bills. The £200-2,500 cost of the solar system could lead to a saving in bills around £100 per year. So straight paybacks are about 20-25 years. The sedum roof does have some insulation and ecological value but in economic terms it is an expensive nice-to-have.
The BRE EcoHomes rating is provisionally 'very good'. For the housing association there is more to this scheme than money - cash savings go to the tenant and no premium is currently added to the rent for this.
Rather, as a committed housing-provider it is prepared to take a long-term view both of the costs and benefits for sustainability.
CONTRACT START 8 March 2002
START ON SITE DATE 24 June 2002
CONTRACT COMPLETION 25 October 2002
PRACTICAL COMPLETION 10 March 2003
CONTRACT DURATION 33 weeks contract (52 weeks actual)
PROCUREMENT JCT with Contractor's Design, negotiated
GROSS FLOOR AREA 203.5m 2(external), 174.8m 2(internal)
TOTAL COST £251,514 CLIENT East Thames Housing Group
ARCHITECT ECD Architects; PRP Architects
ENERGY CONSULTANT ECD Project Services
SERVICES ENGINEER Fulcrum Consulting
MAIN CONTRACTOR Botes Building
SUBCONTRACTORS AND SUPPLIERS Timber frameMTE (Leicester); Aquasol Duo solar hot water system Construction Resources; grey water recycling system Water Dynamic Group; sedum roof Erisco Bauder; ventilation system Passivent; hard landscape, including porous pavingMarshalls; windows Chadwick and Paxman; plumbing Hepworth; green product supply Construction Resources
East Thames Housing Group www. east-thames. co. uk ECD Architects, ECD Project Services www. ecdarchitects. co. uk PRP Architects www. prparchitects. co. uk Fulcrum Consulting www. fulcrumfirst. com Botes Building www. botes. co. uk