"These supply issues highlight how important the upcoming Commerce Commission investigation into home building supplies is," Green Building Council chief executive Andrew Eagles said. Photo: Lynn Grieveson

A shortage of timber is being blamed for unambitious updates to wall insulation standards in new homes, which could have helped New Zealand achieve its climate goals, Marc Daalder reports

The latest annual update to the Building Code will increase minimum insulation standards in new homes and small buildings and require new large commercial buildings to be 20 to 30 percent more energy efficient.

The Ministry for Business, Innovation and Employment said the update represents the largest boost to energy efficiency standards in more than a decade and said it received more feedback on the proposals than for the previous five annual updates combined.

“The new requirements will reduce the energy needed to heat homes by up to 40 percent, allowing people to heat their homes more easily and efficiently, which will lead to positive health impacts and increased energy savings for New Zealanders,” said Jenni Tipler, manager for the ministry’s building performance and engineering work.

The ambition of the new standards was also welcomed by the Green Building Council, which advocates for climate-friendly construction and building practices.

However, the Green Building Council’s chief executive Andrew Eagles said that the improvements could have gone further and been brought completely up to date with international standards.

“We welcome them and the changes to climate zones, but there isn’t enough insulation requirements in the changes to warmly welcome them,” he said.

Insulation requirements for roofs will double and windows will also need to improve, but relatively few changes were made to standards for wall insulation. MBIE said this was due to timber supply issues that would have made more ambitious requirements impossible to implement.

“We received strong feedback that changes to insulation requirements would have to consider timber supply issues and the amount of timber framing in wall cavities,” the Building Code update stated.

“The amount of timber reduces the total wall insulation value and higher insulation requirements may require different framing practices or higher performing insulation products. This would be difficult to achieve for residential buildings across the country at this time. That is why we have left the requirements for walls in residential building mostly unchanged.”

Eagles said the issue put the spotlight on the building materials shortage in New Zealand.

“These supply issues highlight how important the upcoming Commerce Commission investigation into home building supplies is. If this investigation is going to be a success, it has to prioritise materials that will deliver warm, dry, low carbon homes.”

The window insulation requirements for new homes and small buildings will be phased in over two years. By the end of 2023, the standards will be 70 to 90 percent more stringent than current practice, depending on where in the country the building is located.

The new Building Code also split New Zealand into six climate zones, rather than the previous three, to recognise that different regions will need different insulation standards.

Larger commercial buildings, like offices, healthcare centres and schools, will also face new requirements under the update to the code.

Nearly three fifths of submitters favoured the most ambitious option presented by MBIE, which would see new commercial buildings required to use a quarter less energy for heating and cooling than existing standards mandate.

In the end, most climate zones will see a reduction of between 20 and 23 percent. Climate zone four, which covers the central North Island, the Wairarapa and the West Coast, will face the most stringent requirement of a 30 percent reduction in energy usage.

The new standards also differ across building types. Schools, for example, are expected to reduce energy usage by only about 10 percent. Healthcare centres would generally become 34 to 36 percent more efficient, though those in climate zone four would see a 50 percent increase in efficiency.

Offices would be required to use 22 to 34 percent less energy while shops would face a smaller reduction of just 18 to 25 percent.

Most of the changes are expected to be implemented by the end of next year.

Further climate-related building regulations, including a cap on emissions from energy used by building occupants, are expected as part of MBIE’s Building for Climate Change programme next year.

Marc Daalder is a senior political reporter based in Wellington who covers climate change, health, energy and violent extremism. Twitter/Bluesky: @marcdaalder

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