NZ warms to insulated floor slab


A Queenstown company is laying claim to the most energy-efficient floor slabs on the market.

MAXRaft – a Deloitte Fast 50 regional winner – has the only patent in New Zealand and Australia for an underfloor, fully insulated polystyrene slab.

The company’s jointly owned by Queenstown’s Lonsdale and Mackenzie families.

Quantity surveyor Craig Lonsdale invented the product, which was first used for his Queenstown father Gary’s house at Kelvin Heights in 2010.

It’s now been used in more than 200 local homes and is taking off throughout the country.

Local David Reid Homes franchisees Abi and Fraser Mackenzie bought into the company two years ago. 

New Zealanders have traditionally concentrated on insulating ceilings and walls, however up to a third of a building’s heat can be lost through an uninsulated floor.

Gary Lonsdale explains that 80 per cent of heat loss in a floor is through the external edges of the foundation, which a MAXRaft slab prevents.

“There’s nowhere for the heat to escape.”

Floor insulation, he says, is the easiest and most cost-effective way to retain heat in your home.

He says there are both short-term and long-term cost savings.

The short-term saving is about three days’ labour in building a concrete floor.

“It’s taken a long time for some of the old-time builders to get their hear around it because they like hammers and nails, four by twos and stuff like that and don’t like change,” Lonsdale says.

“It’s so simple that they think, ‘oh, something’s not quite right here’.”

But the main benefits, he says, are in energy efficiency – lowering the cost of heating – and increasing people’s comfort and health.

“When used in conjunction with underfloor heating, MAXRaft can reduce the cost of heating the home by 30 to 40 per cent.”

Lonsdale says the cost might be about $2000 dearer than other slabs “but you’re getting the Rolls Royce of floors”.

He notes that the slab’s being used by a number of local home-building companies like Landmark Homes and GJ Gardner as well as David Reid Homes, and is also used by Rilean Construction in its Evolution Series of sustainable homes.

MAXRaft offers a kitset supply package but also installs the prefabricated slab itself.

Lonsdale says his company’s gone to great lengths to get the likes of CodeMark and Homestar accreditation to prove its credentials.

“We have the highest insulation factor which is 4.5,” he says.

In addition to residential work, MAXRaft also supplies floors for a number of local commercial projects.

An early example was the Graze restaurant/cafe building at Lake Hayes Estate.

It’s been awarded the contract for Camp Glenorchy, hailed as NZ’s first NetZero Energy campground and holiday park.

All materials involved have to be recyclable, Lonsdale says.

Fraser Mackenzie believes that in the same way wall and ceiling insulation is mandatory in NZ, there should also be a requirement for insulated floors.