All double-glazed windows in new houses must be significantly upgraded, including pumping gas between the two panes of glass by November next year to meet new Government standards.
The Ministry of Building, Innovation and Employment is bringing in upgrades to the thermal performance of windows in new buildings and although it said it did not specify exactly how that would happen, an industry leader said the gas was a key to compliance.
Brett Francis, chief executive of the Window and Glass Association, said one way to meet the new standards was for Argon gas to be pumped between the double-glazed aluminium-framed units going into all houses by November 23 next year.
Window unit prices could rise by at least 30 per cent to meet the new standards and other upgrades, he said. Aluminium dominates new house and commercial construction joinery, accounting for around 90 per cent of the market.
A thermal break in the aluminium joinery and low-emission glass for better insulation were other requirements to meet the new standards, he said. So it was a three-pronged approach.
The association supports the changes because they will result in better thermal performance of windows.
"This is bang for your buck," Francis said of the new H1 standards and a dramatic improvement in thermal ratings.
Windows are estimated to be responsible for 35-50 per cent of winter home heat loss, an association document on the new energy efficiency standards showed.
"We've always known that the windows are the weak point in the thermal envelope," the association said.
A two-year transition period was seen as acceptable to the industry where products which comply with the older existing standards will be used before the new products are made, distributed and installed.
David Kelly, Master Builders' chief executive, wants the wider thermal housing upgrades delayed by 12 months.
"We support the intent of warm, dry, healthy homes but we're worried it's coming in too fast. We've already got cost increases and construction inflation is running at 18 per cent annually. The estimate from builders is that all the upgraded standards for new houses could add $25,000/house."
Currently, double-glazing is mandatory for all new housing but the two panes of glass only have an air gap as the thermal barrier between them.
The new standards will see that upgraded further by Argon gas being pumped in. That aims gives a much greater thermal barrier between the exterior and interior panes.
By November this year, that new thermal double-glazing standard will apply to most of the South Island so most new houses built from then on will have the gas.
By November next year, the new standard will apply to all of New Zealand.
Andrew Bayly, National's building and construction spokesman, has qualms about the cost added to new homes, although he does acknowledge the need for better energy efficiency.
MBIE says that under the new H1 standard, New Zealand has been divided into six climate zones so the changes are introduced to the coldest or most southern places first.
Glazing experts say that by trapping a measured amount of Argon gas between the panes of glass and sealing it in, the insulating performance of double glazing increases dramatically.
Argon gas is roughly 40 per cent denser than air and acts as a greater barrier to heat loss in the home, with a thermal performance increase at or around 15 per cent.
Homeowners will save on their heating and energy bills if they have the gas-filled glass, experts say.
Bayly said he had heard of the Argon gas leaking out after about 14 years.
Francis said the air gap was 100 per cent filled with gas when the units were manufactured. A study of units which were 10 years old resulted in experts finding only a tiny amount of gas had leaked, he said. The units still performed above their required level after a decade, he said.
Argon gas was used in some houses already, he said, particularly in the South Island.
"It would typically be used by a homeowner who had spent time examining the thermal performance of the envelope of their house, typically more at the higher end of the market, usually in places designed by architects," Francis said.
"This cost increase comes at a time of other cost rises but New Zealand homes have been very poorly built historically," Francis said.
"It's costing the industry a fortune. I know of one window fabricator who will need to throw out $60,000 worth of joinery in his showroom because it won't meet the new standards. He'd' created a mini-house with windows and doors to show off the products.
"In manufacturing, workshops are also having to be re-tooled for the new joinery," he said.
The last time the H1 standard of residential thermal performance was upgraded was more than a decade ago, "so it's long overdue."
The gas could not be added to existing double-glazed windows "because it's a sealed unit. You can't break the seal and re-seal it." Existing units would need to be replaced if homeowners wanted the glazing with gas.
If a double-glazed gassed window gets broken, the glass unit within the aluminium framing will have to be recycled and replaced, Francis said.
"It's a glass unit sitting within an aluminium unit," he said.
"You would take out both panes of glass which would be replaced with new gas in them," Francis said.
David Gittings, MBIE's building performance and engineering manager, said: "We are increasing the minimum insulation level for windows across the country, with a focus on higher upgrades in colder climate zones. This is because windows represent the largest source of heat loss in new homes."
Improved window performance can be achieved in a number of different ways such as using double glazing, the use of Low E glass to improve the performance of a double glazed unit, and by using thermally broken window frames, Gittings said.
The use of Argon gas in double glazed units was one option for how building designers might choose to meet the new window insulation levels, but this is not a requirement, he said.
MBIE had undertaken an extensive public consultation process on the new standard and was bringing it in via a stepped approach.
Ministry officials had convened workshops with industry leaders in the past fortnight to get a better understanding of any issues which have developed since last year's consultation.
"We will continue work with the sector to determine what further support is required and should a decision need to be made on the transition period, we will communicate this as soon as we can," Gittings said.