Grasping the metal

Ealing Family Housing Association's development in Wilton Road, Reading is small - just 25 units have been built on the site of an old laundry. Traditional builders in this country would claim that the only way to construct such a scheme viably would be by brick and block, but Ealing Family opted for steel instead.

Like an increasing number of housing associations, Ealing Family felt that the benefits of factory production could be replicated on a small scale if the architect, contractor and prefabricator worked together to eliminate inefficiencies. Using smaller sites to experiment with new building techniques also means that housing associations are exposing themselves to less risk if there's a steep learning curve.

The architect Rhys Owen claims that the use of steel will help the demonstration project meet the key performance indicators and voluntary targets put forward to the Housing Forum. "There are three broad aims," says project architect Rhys Owen. "One to provide low energy, environmentally friendly homes, two to partner and three to try out steel prefabrication." Specific targets include reducing capital costs and construction time by 10%, reducing accidents by 20% and improving productivity and turnover by 20%. Ultimately the aim is to reduce tenants' heating and water bills, and provide Ealing Family with long lasting homes that require low maintenance.

Crucial to the scheme achieving economies of scale was Ealing Family and Rhys Owen's partnership with Forge Llewellyn, a joint venture formed by steel manufacturer Forge and contractor Llewellyn. Forge has had years of experience of building low energy steel housing in North America and has become accustomed to transferring its know-how to partners.

"The partnership arrangement meant that the design team and subcontractors sat around one table, which meant we had a much deeper relationship than we have on other sites," says Phil Thompson, development manager at Ealing Family. The partnership also helped to avoid duplication, according to Thompson. "You only have to work with one contractor and so you don't have to distribute tenders to six contractors, who then in turn put tenders out to six subcontractors," says Thompson.

He says that it took time to get used to the process but the common goal helped the parties come to a closer understanding. "One thing that you learnt was how every decision you make has a ripple effect around the whole project," says Thompson.

Thompson says that the whole project was easier to cost than a traditional site. "We designed out most of the risk at the outset. Between us we did research on the ground conditions and the design and build, which meant we knew what the costs were going to be." At Wilton Road, Forge Llewellyn showed labourers how to erect steel frame structures on site, and despite having no previous experience the workers were constructing frames in a matter of hours after only a day's training. "There is a learning curve with steel frame but once you've done ten units you'll be committed for life," says Owen.

The main objection to steel says Owen is its lack of tolerance. "With steel there is only a 5 mm grace. The slab or beam and block has to be level and traditionally this hasn't been important. We have to improve build standards. We must impose accuracy on the bodge trades." To reduce construction time the development team chose a precast ground beam and piling system together with a Roger Bullivant extruded floor system. Ealing Family's Thompson says that because the foundation and steel frame had to be constructed accurately there was less likely to be a problem on site.

"The steel frames were erected and covered on site very quickly, which meant that we could get on with working inside," he says.

The team was also impressed with the quality of finish. "Dimensionally steel is more stable than brick and block. There's no dry shrinkage and we haven't seen one hairline crack," says Owen. This means fewer defects, which was another key performance indicator measured by the Housing Forum.

It is also possible to achieve very low U values using steel. "We wanted to make the walls thicker to enable more insulation, in other words create a 6 in rather than 4 in wall frame. With timber frame it would have been more expensive because you would need more solid wood than you would need steel." Using Rockwool insulation Owen aims to achieve U values of 0.16 for the walls, 0.12 for the roof and 1.3 for windows, well below the proposed changes in Parl L of the Building Regulations. "Like Mount Everest, an ultimate U value of 0.1 exists, so architects will strive to reach it," says Owen.

As a result of these high thermal standards heating loads are less than 2kW, which means mechanical heat recovery ventilation systems can be used rather than conventional radiators and boilers. These systems use outgoing warm air to heat incoming fresh air, and a gas heating coil provides a boost if necessary. New systems from both Baxi and Max Fordham are being used at Wilton Road.

There are large potential savings on heating bills for tenants using these systems. Ealing Family's Thompson says that yearly heating bills could be as low as £30, which would be three-to-four times cheaper than in a conventionally-heated house. Green technology also means cut-price water bills for tenants. Rainwater collected in Eco-vats installed under ground is recycled and used for washing machines and toilet flushing.

"These low energy systems shouldn't just be for the middle classes. The technology doesn't cost that much," says Owen. "We want to bring the 'one-off' to the mainstream. The housing associations will show the spec developers the way." With Rhys Owen and Forge Llewellyn set to build another 64 units for Ealing Family in nearby Edgar Road and private developers trying out prefabrication on an ever larger scale, the portents for steel are good. Within the next few years we will know whether private developers have followed the pioneers' lead and made ultra-efficient, high-quality, prefabricated homes the norm.