Baby, it's cold inside: Half of Kiwis say homes aren't warm enough

Thursday, 25 June 2026

Some New Zealanders are living in homes that are so cold during winter that they can see their breath, a major new study shows.

The Building Research Association (BRANZ) intensively monitored temperatures and energy use in about 260 homes between 2022 and 2025 for its HEEP-2 study - an update on similar research done 20 years ago.

The research found that although homes have got warmer over the intervening two decades, many people were still putting up with indoor temperatures below healthy levels.

BRANZ senior research scientist Vicki White said temperatures in living rooms during winter evenings were now above the World Health Organisation recommended minimum of 18°C, with average measurements of 20.4°C recorded between 5pm and 11pm.

A big part of that was the widespread uptake of heat pumps since the first HEEP-1 study was done.

'In HEEP-1, about 1% of the households in the study had a heat pump, and now we've got over 60% of households in New Zealand with a heat pump,' she said.

'Evidence from HEEP-2 suggests people are using them to heat their main living areas, particularly in the evening period.'

That was the 'good news story' from the study, but at other times of day houses were often still colder than that 18°C minimum, White said.

One in five households said they could sometimes see their breath inside during winter, and nearly half (48%) said their house was colder than they would like sometimes.

Bedrooms were especially cold, with average temperatures of just 16.5°C overnight.

Otago University healthy housing researcher Lucy Telfar-Barnard said the proportion of occupied bedrooms that were never heated was particularly worrying.

The research found 41 percent of adult bedrooms, 42 percent of school-aged children's bedrooms, and 31 percent of bedrooms that babies and pre-schoolers slept in, were never heated at all.

'Hot water bottles in bed and those sort of superficial things, they make a difference to our body temperature - but the temperature of the air going in and out of our lungs makes a difference to how our lungs function,' Dr Telfar-Barnard said.

'When it's consistently cold, then our lungs get inflamed and … they're not well placed then to fight off those bugs that come in.'

Cold air could also be a trigger for people with asthma, she said.

The study also included a sub-set of new homes built to higher standards.

Green Building Council market transformation director Sam Archer said his organisation was pleased to see those houses recorded average temperatures above the 18°C minimum, around the clock.

'It's not just the average temperature, it's also the consistency of temperature,' he said.

'They're higher, and they're keeping to temperature in the morning, during the day and the evening and at night, when people are sleeping in bedrooms.'

The overall improvement in temperatures since the last survey 20 years ago showed the benefit of government programmes like Warmer Kiwi Homes, Archer said.

That had provided $80-100 million a year to subsidise insulation, heat pumps and other retrofitting in lower-income homes, but at the moment the programme was not funded past June 2027.

'There's real concern that… the future of it is in doubt.'

The programme should be continued and even expanded, he said.

'Our houses are not insulated properly, we don't have double-glazing, and we don't have enough funding and enough money going into improving especially homes in fuel poverty.'

Overheating an emerging risk

The study also highlighted an emerging risk: houses that are now too warm in summer.

One in five households included in the study said their home was always or often warmer than they would like in the summer months.

A quarter of bedrooms recorded average temperatures of 24°C overnight - meaning they were 'primed to overheat' during the day when outdoor temperatures rose again, the study report said.

Vicki White said 26°C was used as a standard threshold to define overheating, but even at 24°C occupants could start to feel uncomfortable.

There had been an increase since the first study in people using 'active cooling' such as air conditioners and fans, but not to the same extent as they heated their homes in winter, she said.

There was a strong link between outdoor and indoor temperatures, so as the climate warmed more houses were likely to start overheating, she said.

'That has really significant implications for energy hardship, especially in summertime when we're used to saving a bit on our power bill.'