The right foundation keeps warmth in and power bills down.
Cold will always be a part of winter, but freezing floors in your home shouldn’t be. While the focus tends to fall on wall and ceiling insulation, nearly one fifth of all heat dissipation is routinely ignored, even though the source of the loss is right beneath our feet.
That’s why MAXRaft general manager Henry Edney says starting with an insulated slab is the smartest way to build.
“The slab can sap heat from a house, which is why insulation is so important,” he says. “When you stop that process with insulation, you get a warmer, healthier home – and lower power bills for life.”
BRANZ guidance published in Build Magazine highlights that a significant share of slab heat loss occurs at the vertical edges, which is why recent New Zealand Building Code changes now require higher R-values – a measure of how well insulation resists heat flow – starting at R1.5 nationwide and rising to R1.7 in the coldest regions.
Edney says the advantage of keeping the heat in isn’t exactly rocket science, and means a warmer, healthier home while reducing power bills over the long term. “While the Building Code typically expects a lifespan of 50 years for a new dwelling, most of us are aiming for a good hundred years. And even if the reduction in monthly cost is relatively small, over the full duration it’s a big saving.”
What is better than any future savings is a warmer, snugger home daily, particularly when adding an insulated slab from the outset, which adds less than 1% to the cost of the build. “It’s not a big outlay, typically in the region of $3000 as part of a $700,000 to $800,000 project. But it is a big, lasting benefit,” he confirms.
Heat loss in traditional concrete slabs occurs through the sides as well as the base.
“When you insulate, you stop that heat loss. Your heat pump or underfloor heating doesn’t have to kick in quite as often, so you’re using less energy. And because there’s edge insulation along with underslab, the energy which could leach to the outside is kept inside,” Edney explains.
A cold slab gets its kick to the kerb with MAXRaft’s ‘bathtub’ system of insulation beneath and around the edge of the concrete. That means no direct contact with the cold earth or exterior elements.
“When perimeter heat loss in the slab is prevented, wall insulation works far more effectively – improving performance by 30–40% and creating a continuous thermal envelope,” says Edney.
And, of course, the insulated slab also prevents moisture, contributing to a drier, mould-resistant home.
A peek into the production process reveals that every MAXRaft installation is custom designed and cut at the factory, with the insulation packed into site-delivered kits. The onsite builder places the MAXRaft into the foundation much like a jigsaw before pouring the slab.
“It’s about getting it right the first time, and for good reason. Continuous insulation ensures energy can’t ‘leak’ at weak points. There’s nowhere where the concrete touches the ground. And then there’s consideration of the environment – pre-cutting in the factory means far less waste, and offcuts are recycled rather than the builder’s skip,” says Edney.
Asked if builders or installers need special training or support on site, or if introducing a MAXRaft slab into building plans requires additional overhead in terms of consents or other tasks, Edney says the best advice is to plan ahead. “The slab is specifically engineered for the site. That means we are involved long before the builder is on site, so everything dovetails neatly, and your project schedule isn’t affected.”
By working with homeowners, builders, architects, and developers, and with partnerships including Architectural Designers New Zealand, the Passive House Association, and more, Edney says the message and the value of insulated concrete is quickly catching on. “It just makes sense,” he says. “And it adds value to your home. Both in terms of its liveability, and when it comes time to sell.”
It’s a view borne out by market movement: from 2014, the Queenstown-headquartered but national operator’s installations have surged from 100 to more than 1000 annually, accompanied by the growing shift towards whole-building efficiency.
Ultimately, Edney’s message is clear: starting with a great foundation is always a firm path to lasting value. Spending a little more upfront on a MAXRaft slab means a warmer, drier home from day one, and well into the future.
Find out more at www.maxraft.co.nz.