New Wall Board Blocks Off 'Thermal Bridge'

Foundation for Research, Science and Technology

Timber planks that double as inner and outer walls of houses but boost insulation and cut heating costs, are being marketed by La Grouw Corporation, which builds Lockwood precut housing.

The planks sandwich insulation material such as polyurethane or polystyrene into a cavity between them.

"We've overcome the 'thermal bridge' - studs and dwangs," says La Grouw research engineer Gerry Lane.

"We've done away with them because heat inside a house is conducted by them to the outside."

The research project that led to production of the planks was supported by Technology New Zealand, which invests in research into new products, processes or services as part of the Government's plan to fashion a knowledge-based economy. The planks were developed in response to new energy efficiency documents

issued by the Building Industry Authority, which oversees the country's building code. "The documents aimed to reduce the amount of heating energy required in the home," Mr Lane says.

"Heat travels across studs, dwangs, joists, weatherboards, gib boards."

The documents specify an R value of 1.0 for solid timber - the R value being the resistance value of thermal heat transmission. Mr Lane says that he and his La Grouw team of Paul Wade and Kerry Treloar set about doing something with solid planks.

They experimented unsuccessfully with lamination as a heat-loss solution, but then found that a 97mm-thick plank, including the insulation packing, was the answer. It also met theBIA requirements.

Mr Lane says La Grouw built a trial house at its Rotorua yard last year to test the concept.

"It worked and so it's now being marketed  both here and overseas, particularly in Japan. We've got a product, as well as a process now and they've been patented."

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