GMV is providing the power for the 1377 homes and other buildings in the village. That does not however mean a big power station on the Thames-side site; in keeping with the scheme's green objectives the developer is building six much more environmentally-benign and discreet combined heat and power (CHP) energy centres.
This is the largest new build residential scheme in the UK to apply CHP to date, alongside other green measures ranging from water-saving taps to a wind turbine. The motivation for applying this technology is the set of project targets that GMV has set itself covering build efficiency, cost, and environmental and sustainability issues. It has committed to meeting four environmental targets over the five-year project: reducing primary energy consumption for a typical home by 80%, embodied energy by 50%, construction waste by 50% and water use by 30%.
Two phases into construction, however, GMV is finding its green targets hard to hit. "For a lot of the things we are trying to do, we are finding the supply base isn't there," says Hammond. Not only suppliers, but subcontractors, homebuyers and even the government are having to be educated as the homebuilding process and its product are greened. And then there's the issue of cost. "One has to accept that the cream of environmental solutions will be expensive," says innovation consultant Richard Hodkinson of Richard Hodkinson Consultancy.
The scheme's adoption of CHP is catching attention, even though it has long been applied in the industrial sector. "Because this is the first application on a large private new build scheme we'll learn a lot," says Hodkinson. "We've already learned some big lessons - like not to oversize the plant, and how to procure. We actually had it done as part of the usual building services design" (see box). GMV owns the energy centres and has awarded Alstom an initial 30-month contract to manage the facilities. "After that our options are open - we could sell them, or the village's management company could own them," says Hammond.
CHP plays the key part in meeting the target to reduce primary energy consumption, allied with improved insulation, air-tightness and managed ventilation to bring homes' U values down to 0.3. But GMV remains 15% short of its 80% target, and plans to fill the gap with the aid of renewable energy, installing a wind turbine and photovoltaic panels.
Embodied energy content of building materials and components is being assessed using BRE's Green Guide to Specification, which gives products an A, B or C rating based on environmental criteria, costs and service life. By using A and B rated products, GMV has achieved a 25% improvement, and for the next build phase aims to use A grade products, like timber, terracotta and render.
GMV is well on the way to hitting its waste reduction target of 50%, by applying another BRE innovation, the SMARTWaste software system. So far the average reduction is 35%, although individual results of up to 65% have been recorded. Results have not been achieved without some hard lessons though. "We learned it is important to build plasterboard recovery into the drylining contractor's tender package. On phase two of the scheme we didn't and when we tried to include it later, we were quoted a price of £60 000," says Hodkinson. "It raises the issue of who takes responsibility for minimising waste," adds Hammond.
Water reduction is proving the most elusive of targets, with GMV half way to its 30% saving and struggling to see how it will find the other 15%. The scheme has water saving taps and cisterns and rainwater is being harvested, but more has to be done. "Environmentally this is an important issue, and water is going to cost a lot more in 10 years, but we don't have a lot of room for manoeuvre," says Hammond. "Grey water recycling is hard because there is no standard for recycled water. Without a standard we are not prepared to provide anything that goes back into the house that's not potable." That's a message for government.
Built Environment 2001
Greenwich Millennium Village will be one of a number of major UK building projects featured in a busy seminar programme at Built Environment 2001, the new conference and exhibition for building professionals. The event, at the ExCeL Centre in London Docklands on 16-18 October 2001, is being organised by Building Homes publisher The Builder Group and United Business Media International. To register to visit call the Ticket Hotline on 0870 4294542.CHP at GMV - one user’s guide
For CHP to be viable, there has to be a balance in power demand. Mixed use schemes are ideal, as homes source energy morning and evening, while commercial buildings source it during the day. Superinsulating homes at GMV would not have been worthwhile as it would have reduced power demand to such an extent that CHP would no longer have been viable. Development must be fairly dense because heat distribution mains are expensive - it costs about £300 a unit to distribute heat to a block of apartments, but £1000 a unit for low-density housing. By phasing development of energy centres alongside homes, GMV spreads investment in CHP. The first energy centre is in the basement of an apartment building and serves 100 homes, the second is among houses and serves 450 units. “Generally the minimum number of units you can have for CHP to be economically viable for homeowners is 200, because it costs £20 000 a year to maintain an energy centre, which produces a standing charge of £100 a year,” says Hodkinson. CHP achieves the best reduction in CO2 emission levels, according to Hodkinson. While the average home produces 3.5 tons of CO2 a year, the most efficient boiler/insulation combination would bring that figure down to 1.5 tons. With CHP emission levels are around 1.1 tons. “The downside is that if you wanted to offer the cheapest solution you wouldn’t go for CHP,” admits Hodkinson. While the most efficient boiler/insulation solution brings annual heating cost of the average home down from around £480-500 to £280, CHP shaves at most £80 off the fuel bill.Source
Building Homes
Credits
Developer Countryside Properties/Taylor Woodrow Capital Developments Housing associations Moat Housing Association, Ujima Housing Association Architects Ralph Erskine (masterplan), EPR Architects, Proctor Matthews Planning consultant Montagu Evans Innovation consultant Richard Hodkinson Cost consultant WT Partnership Environmental engineer Taywood Engineering Structural engineers Waterman Partnership, Thorburn Colquhoun Services engineers WSP, Thorburn Colquhoun Landscape architects Randle Siddley Associates, Robert Rummy Associates