Northern Exposure

SIPs use has been growing in North America and now Bellway Homes is the first major homebuilder to erect a SIP house in the UK, at Tudhoe, County Durham. The SIPs are made by Scottish producer BPAC - which has gone into production after experimenting with SIPs for a couple of years. The panels were used for both walls and roof, turning the standard Bellway Montague housetype from a three-bed to a five-bed room-in-the-roof home, thanks to the open loftspace created by using SIPs.

Ian Skeoch, Bellway group product development manager, has been closely associated with the scheme. "We are very pleased with how it has gone together," he says. "There are a lot of things going for this method of building. We combine really incredibly low U values with tremendous speed of construction. In addition you get a room in the roof without the need for attic trusses. We are just starting on a scheme in Portsmouth using Fillcrete's Tradis system and when we've finished we will be making a detailed evaluation of both." The Tradis system has been around for a couple of years - it won the Building Homes Innovation Award in 1998 - and combines Masonite I beams with Warmcel cellulose insulation. But SIPs panels are different to Tradis as their strength derives from the effect of glueing an inner and outer sheet of board around a sheet of rigid insulation - most commonly expanded polystyrene.

The panels are factory-manufactured and assembled on site using a series of timber splines to act as sole plates and connectors. Additionally the system allows openings to be accommodated without the use of a lintel above.

In an era of lower and lower U values, SIPs may represent the future for homebuilding. Instead of adding insulation to the structure, the insulation becomes the structure. On the Bellway scheme, BPAC has used a Vencel Resil EPS sandwiched between a 9 mm OSB inner and a 15 mm breathable outer board from Egger, DHF. By combining these boards, they have nullified the need for an external breather layer. Overall wall thickness is 120 mm but the U value is just 0.29. Roof panels are made in a similar way but here the EPS has been increased from 95 mm to 145 mm, resulting in a U value of 0.22.

BPAC's panels were erected in a day and a half by Elphinstone & Howarth, a Shetland-based timber framing crew. Bobby Elphinstone says: "We saw a SIPs demonstration house in Dallas last year and were impressed by how well it went together. We thought it looked ideal for the extreme weather conditions of Shetland where virtually all housing is timber frame. We were therefore keen to work with BPAC and plan to use these techniques on our own projects soon." Besides BPAC, other makers are entering the market - including Kingspan which bought German SIPs manufacturer TEKHaus at the end of last year (see factfile).

Tony Palmer, who runs SIPTEC, has been experimenting with different composite panels and has conducted testing at both the BRE and the University of Surrey and plans to build some SIP homes for Willmott Dixon.

Palmer has worked with the BRE on a proposed testing and certification programme and plans to take the SIPTEC system to the UK market via strategic partnering, joint ventures and licensed companies operating under his company's BRE certificate. Under the scheme the BRE will train and certify SIPTEC erection crews.

Raymond Durber's Angel Design is another SIPs business, and has close links to US manufacturers. Durber has plans to open a SIPs school here as well as manufacturing panels. "There is more to SIPs than just producing the panels. There are specialised tools and techniques required to build well with SIPs and we have to be able to teach these before we can unleash SIPs building into the UK. It's useless to build panels without the necessary back-up," he says.