Warmth without the width

Things have turned out splendidly for Persimmon Homes. The builder has managed to keep up with the spiralling insulation demands of the Building Regs without increasing the thickness of the insulation it uses.

"We didn't have to make any changes to the overall construction to meet the new Part L Building Regulations," says a happy Nick Ashfield, Persimmon's project manager for a just-completed development at Hatfield.

The trick lies in the use of Springvale's new Platinum Wallshield expanded polystyrene (EPS) insulation board, which gives 15-20% better thermal performance for the same thickness as other EPS panels. Using it meant Persimmon did not have to make any big changes to its traditional construction methods, such as increasing the width of the walls to take thicker insulation panels.

Adopting the same construction methods as on previous sites, Persimmon installed the new boards as partial-fill cavity insulation backed by standard aircrete blocks. The better thermal value was enough to boost the wall insulation to the higher standard set by last year's Part L.

Getting better U-value for the same insulation thickness shields construction teams from having to spend time and resources on adapting their building techniques. It also lets them keep their buildings within the same footprint as before – no space is sacrificed on the altar of the Building Regs.

Space is always at a premium. With residential site layouts in the South-East so very tight, housebuilders don't want to increase the width of the walls because it could mean losing a house or two on a development. Add to that the recent scuppering of several high-profile developments for too low a housing density and the likely cranking up of density requirements in PPG4, and better insulation that doesn't encroach on space looks even more attractive.

At Hatfield, Persimmon used more than 11,000 sheets of Platinum Wallshield to build 91 houses. The boards are light – one hand is enough to lift them – and easily cut with a handsaw. "Our contractors love working with it," says site manager Mike Ellen. "They find it installs quicker and, being silver grey, is less glary to work with than traditional white systems."

Persimmon also used Springvale's BeamShield insulated flooring at Hatfield, infilling the concrete T-beams with the EPS panels instead of standard thermal blocks. BeamShield EPS panels offer a far higher insulation value than thermal blocks and can meet the new 0.25 U-value requirement on their own.

Enquiry number 203