By Phil Pennington for RNZ
Officials have pulled back from the boldest approaches to making houses warmer, because of the stresses on the supply chain.
They aim to go part of the way to upping demands for better roofs, windows and floors, but not as far as architects and environmentalists want them to.
Officials will announce eagerly-awaited new standards for insulation in the Building Code at the end of the month, in what is a key to climate change moves by government.
New Zealand has woefully poor housing stock, and slacker standards around cold and dampness than many OECD countries - even though warmer houses are known to save lives.
Recently, the government has made insulating homes central to addressing the climate emergency.
It could have kicked off a radical programme of "building for climate change", by opting to match or go even beyond international standards.
That's what Institute of Architects chief executive Teena Hale-Pennington pushed for.
"We certainly were - we see that as a huge opportunity to benefit all New Zealanders by shifting and being ambitious," Hale-Pennington said.
However, supply chain ructions due to the pandemic are forcing up prices, inflation and wait times.
"Our ability to put these new changes into place is dependent upon having those materials and supplies available.
"I think we ultimately will get the outcome that we're all looking for... it's just going to take a little bit slower, more cautious start."
Especially for housing, which Hale-Pennington expects to lag behind any upgraded standards for commercial buildings.
The Ministry of Business, Innovation and Employment will not hint at what rule changes are coming.
"More submissions were received for this consultation than the last five years of Building Code updates combined," it told RNZ.
It looked at four options, ranging from the status quo, to a "tweak", to radical upgrades - with price tags to match, ranging from $1800 extra on a four-bedroom build to $50,000.
The Institute of Architects, and the Green Building Council's chief executive Andrew Eagles, expect standards for warmer windows - by mandating better double-glazing - ceilings and floors are likely in colder places.
However, though the ministry opened up a discussion about making walls thicker - shifting from 90mm framing to 140mm as standard, so more insulation can fit in - this looks like a no-go.
Eagles said supply ructions were real, but the government needed to sort it out and "crack on".
"That's absolutely essential because our Building Code is woeful by international standards."
The current minimums were set in 2008 at levels lower than parts of the world with similar climates.
"We are at the foothills of significant change," Eagles said.
"We have not got six years.
"We need to gear the industry up, to show them that this is real ... marking out within two years that you can deal with supply chain issues, that you're going to get that 140mm.
"And further, there's going to be even bigger changes three years later."
Thicker not a problem
Building thicker walls in thousands of houses is not the capacity problem it might appear to be.
Major sawmiller Red Stag's chief executive Marty Verry said so long as the space between studs was increased - by changing the standard - the amount of timber going into a house would be much the same.
"Our feedback [to the ministry] ... is if you are making, let's call it, six-by-two, instead of four-by-two, then you can actually get more of that volume out of a sawmill.
"So this change would actually increase the volume capacity out of the sawmilling sector in New Zealand.
"There's less sawing and there's less planning and there's less processing. And there's less losses," Verry said.
While timber shortages were the worst they had ever been, these were not a reason not to go to wider frames, he said.
"We've had limited consultation and certainly haven't been considered prior to making this final decision.
"If the reason is they don't want to put pressure on the sawmilling sector, then that's a decision we really haven't had a chance to enlighten them on."
Refiguring timber framing should be looked at once immediate pressures eased, Verry said.
Studs spaced farther apart present another gain - research last year shows about a third of a wall is made of timber, much more than was assumed, and it leaks warmth from inside to the outside; calculations that set insulation minimums have not taken account of this properly. Widely spaced studs would cut down such thermal bridging.
The Green Building Council believes buyers can cope with the tougher Building Code, as builders learn the ropes and extra upfront costs pay for themselves over time.
The annual health benefits of better insulation have been put at at least half a billion dollars.
The ministry said to take the boldest approach required a "change in direction from the current ways of designing and constructing buildings".
"A longer transition period and a phased approach to implement these changes would be expected."