New Zealand has no airtightness standard for buildings, including houses — and the Green Building Council says that gap is leaving homes cold, damp and hard to heat.
The council held a demonstration of an air sealant technique at a 145-year-old Castle St flat in Dunedin last week, aimed at showing landlords and builders a cheaper alternative to traditional retrofitting.
The flat meets Healthy Homes standards, but tenants there say they still feel the cold.
The Green Building Council demonstrated a low-cost air sealing method in a 145-year-old Dunedin flat, as it calls for NZ to catch up with countries like the UK on airtightness standards. (Source: Breakfast)
"We'll just put the heat pump on for 10 minutes, or as little as we can, and then just layer up, put a thermal, a hoodie, and then my puff jacket and a beanie on, basically just stay warm," tenant Toby Fox said.
"There's little gaps everywhere, and you basically just feel the draught within 20 minutes again."
The Green Building Council hoped the demonstration would prompt more companies to offer airtightness methods to improve housing stock.
Maintenance managers told 1News the cost and disruptions from retrofitting older housing stock could be difficult for landlords.
"It can be very invasive, especially if you're doing the traditional way, you've got to have people up in your ceiling and putting insulation in, flashings," Jason Marks said.
Aero Solutions founder Chris Caiger said the "traditional" method of making homes more energy efficient "would be to tear off the linings, put insulation in the walls, put the things back".
"That's going to cost you about $200,000," he said, estimating air sealant methods would require about 10% of that cost.
The landlord of the Castle St home got a discount for allowing a demonstration of Aero Solutions' method, used commonly overseas but rarely in New Zealand.
Green Building Council senior residential manager Matthew Cutler said there wasn't a requirement for airtightness or pressure testing in buildings here – including houses.
"That is quite rare across the world. In places like the UK, every single new home has to have a pressure test before it can get its final certificate," he said.
He said New Zealand's rules need to change.
"By not having requirements or expectations around airtightness, that leaves it to luck, really, as to how much control a homeowner and occupant has over their ability to control their interior environment."
How to stop the draught
The method on display at the Castle St flat required emptying the property the day before, then putting in the product.
Caiger said adding air sealant and draught stoppers at the flat brought the level of warm air escaping, known as air changes per hour, down from 16 to under two.
"Because we've pumped up the pressure, the inside of the house is at a higher pressure than the outside of the house. And so all the air is blown out. And as it's blown out, it takes a sealant with it. And the sealant gets squeezed through these little gaps. And it clumps back together again, and it forms a cork," Caiger said.
Ministry seeking a NZ-wide approach
In a statement, Ministry of Business, Innovation and Employment building performance and engineering manager Dave Gittings told 1News airtightness was "just one factor that contributes to a healthy and comfortable home".
"It needs to be considered alongside things like ventilation, internal moisture, heating, cooling, solar gain, and overall energy efficiency. It should be noted that focusing on just one of these areas can sometimes create unintended consequences elsewhere."
Gittings said MBIE was developing a nationwide approach to building "to improve indoor environmental performance and reduce overheating.
"Airtightness is one part of the picture."
The ministry was engaging with international experts and organisations "to learn from overseas experience and make sure any future changes are backed by evidence and suited to New Zealand's climate, housing types, and building regulations".
Meanwhile, the Green Building Council wanted new, affordable solutions here.
"We absolutely need a change of thinking in the way we build, and airtightness is a big part of that. So, any companies or any solutions that can come in that are already proven overseas will be a big part of improving our housing stock."
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