Green piece campaign

The architect's designs for the 11 houses at Watton Green don't look like those of a traditional social housing development. Stepped frontages, bridging storeys, rooms in roofs, Trespa panels and cedar cladding set the development apart from the monotonous 1960s-built housing found on much of the surrounding Castle Vale estate in Birmingham, and from much social housing built since.

The development represents the determination of housing association Prime Focus to offer its tenants quality homes, as well as low rents. "Social housing is stigmatised by its appearance," says Gordon Malcolm, contract services director at Focus. "The issue is to come up with varied design, and elements introduced by the architect PCKO have stretched this further."

PCKO's design brief was to address the issues of form, density, versatility, energy efficiency and environment and it has done this in a number of imaginative and innovative ways using Fillcrete's system of Tradis timber-frame insulated wall panels and roof cassettes. The Tradis system plays a key part in helping the scheme to meet its demonstration project objectives of reducing capital costs, construction time, defects and accidents while increasing space standards, exceeding SAP levels and promoting sustainability.

"Panels give you enormous flexibility and they form a weatherproof, high-performance envelope," says Peter Chlapowski, director at PCKO. "Such large structural components allow you to use cantilevered frames. If you were building a simple box, then it's just as easy to use brick and block but for overhanging or bridging elements it's easier to build in timber."

PCKO has incorporated two bridging storeys in its design, each with pitched roofs. Stepped back from the homes either side, the clear spanning elements bring visual interest to the terrace and provide access to the rear of the buildings. The terrace also varies in height along its length and the cladding combination of render, brick, cedar and Trespa panels also helps to bring a distinctive identity to the homes.

One benefit of insulated timber-frame panels that will be immediately apparent to tenants is the habitable roof. The roof panels allow uncluttered, high-ceilinged spaces with galleries to be created in top-floor rooms. The rooms in the roof at Watton Green will help increase overall living space by 10% according to Focus's Malcolm.

Less apparent to the home dweller will be an innovation borrowed from the commercial building sector. The combined services and ventilation core that runs from ground floor to rooftop provides easy access to services and enables more flexible internal layouts. The service pipes emerge from the roof and are concealed in a specially designed chimney.

The use of timber panels should also help reduce tenants' fuel bills. Fillcrete says its Tradis panels have U values of only 0.19 thanks to its Warmcel insulation material, made from recycled paper. Graham Nield, technical manager at Fillcrete, is keen to point out the environmental benefits of the system. "We are commercial eco-warriors. There are no toxins in the timber and no resins are used at all. The Masonite beams require no treatment and the recycled paper is coated with naturally occurring substances," he says. "This is good for the tenants." Other environmentally-friendly features in the homes include low-flush WCs and Passivent passive ventilation.

Focus does not expect to pay a huge premium for its spacious and sustainable homes. Although the Tradis system costs more it is hoped the premium will be recovered by savings on site from faster build times and fewer trades. "We will be charging a normal rent. There's nothing here that will incur significant financial penalties," says Malcolm.

To keep costs down PCKO designed the homes to make the most of factory production. "We used as many standard components as possible so there is the potential for volumetric construction and pods in the future," says Chlapowski.

"The aim is to achieve a seamless factory-built product," says Malcolm. "We had to translate the design into a deliverable system. It's about getting the factory detailing right, so we don't have to do it on site." Tradis has not been used widely in the UK and Malcolm acknowledges that all parties in this project are on the early part of the learning curve. This is evident on site for while many of the panels arrive complete with insulation, window frames and glazing, others do not, generating extra site work. Despite such teething problems, Malcolm is keen to realise the system's potential with another project in the pipeline using the same team and methods. "This product has tremendous potential and we need to develop partnerships to make it work," he says.