Major BRANZ Study Reveals Marked Gap Between Perceived And Actual Health Of Kiwi Homes

In the only national study of its kind for 20 years, nine out of ten Kiwis consider their home to be a “healthy” place to live, even though many still experience cold, damp, condensation and mould, and wish their home was warmer.

The landmark study is collecting data from over 750 households across Aotearoa New Zealand. This includes a survey of 425 households, with 287 of these being monitored for energy usage and indoor conditions.

Data from the household survey and early data from a smaller group of 125 homes monitored over winter 2023 show that homes – especially bedrooms – are warmer than when BRANZ last conducted this study 20 years ago. However, nearly half (48%) of the survey respondents said they had mould in their home (11% said it was larger than a sheet of A4 paper) and 33% said their home was damp at least some of the time.

Around 1 in 5 said they could see their breath inside and a similar amount said their home was cold enough that they shivered at least some of the time in winter.

Homes warmer than 20 years ago

While average daytime and evening living room temperatures in the homes studied exceeded the recommended healthy minimum of 18°C, average night-time bedroom temperatures remain too cold, with some significantly below the ideal.

According to BRANZ General Manager Research Dr Chris Litten: “The overall results suggest that home temperatures during winter are better than they were twenty years ago, but issues of damp, cold and mould persist.”

Evening living room temperatures have risen from an average of 17.8°C to just under 20°C, and average night-time bedroom temperatures have increased from 13.6°C to 16.1°C, which could reflect an increase in the number of bedrooms that are heated as well as increased levels of insulation.

Unhealthy night-time bedroom temperatures are more common among lower-income households in the study. Bedrooms for young children were more likely to be heated than for others, however, around 1 in 3 reported never heating these bedrooms.

Homes are getting healthier, but faster progress is needed

“It’s good to see an increase in bedroom heating and temperatures. This suggests that improvements in insulation and thermal performance are having the desired effect, but building better needs to remain a focus,” says Dr Litten.

BRANZ is extending the scope of its original research to explore how energy can be used more efficiently, making living costs more affordable and reducing carbon emissions, while also making it easier to keep homes warm and dry.

“Underheated homes, ill health, and the financial stress of energy bills are a reality for many Kiwis. BRANZ is investing in this research to gain insights that will support positive change towards quality housing, affordable living, and efficient and effective energy use.”

“Accurate, up-to-date, and accessible data on home energy use and indoor conditions will help inform policies and initiatives to help New Zealanders live in healthier homes while using energy effectively and efficiently,” Dr Litten adds.

These new findings are the first early insights from the new study, focusing on winter heating, comfort, and internal temperatures. Following further data analysis, additional insights from the study are expected to be released in early 2025.

About the study

The Household Energy End-use Project 2 (HEEP2) is a comprehensive national study of energy use and conditions in New Zealand homes designed to replicate the earlier HEEP1 study undertaken in 1999–2005. These are initial findings from HEEP2, which involves a national sample of over 750 households with data collected in various ways, including self-completion and on-site surveys, in-home monitoring and accessing metered energy data from retailers. Households are monitored for at least 12 months and data collection is due to complete in April 2025.

BRANZ partnered with Stats NZ Tatauranga Aotearoa to recruit households via its Household Economic Survey. The survey data presented in this first HEEP2 report is derived from the in-home interview and building and appliance survey completed for 425 households throughout the country. The detailed temperature analysis is based on a subset of 125 of these households monitored over winter 2023. As this represents less than half the HEEP2 monitored sample, these results are preliminary only.

This research is funded by the Building Research Levy, with co-funding from the Ministry of Business, Innovation and Employment Hīkina Whakatutuki. New Zealand Green Building Council provided additional funding for a related Canterbury-based high-performance and code-minimum study, which will be reported on next year.

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