Around a third of homes too cold in winter and too warm in summer
29 January 2020
Data from the 2018 General Social Survey (GSS) shows a third of New Zealand homes are too cold in winter, and over a
third are too warm in summer, Stats NZ said today.
As part of the year-long survey, Stats NZ took temperature measurements in approximately 6,700 homes.
“This is the largest-scale temperature measurement carried out in New Zealand to date and represents a snapshot at the
time of each GSS interview,” wellbeing and housing statistics manager Dr Claire Bretherton said.
The average (mean) temperature recorded inside homes during a GSS interview was 21.4oC. Temperatures in winter, however,
were colder, at 19oC. In contrast, the average temperature recorded in summer was 23.9oC. Indoor temperatures recorded
during the survey ranged from near freezing in a small number of homes to over 30oC in others.
“Most temperatures were recorded between late morning and late afternoon,” Dr Bretherton said.
“We measured temperatures where the interview took place, likely to be in a living room or kitchen, which are more
commonly heated than bedrooms or other parts of the home.”
Housing in Southland was significantly cooler than the national average in summer (with a mean recorded temperature of
21.6oC), while Gisborne/Hawke’s Bay and Bay of Plenty, averaged over 25oC.
The Household Energy End-Use Project, a study by the Building Research Association of New Zealand, rated 20–25oC as a
comfortable indoor temperature. Of all summer temperatures recorded by the GSS, 36 percent were 25oC or more.
“These high temperatures can make people uncomfortable,” Dr Bretherton said.
“However, of most concern is that in around a third of homes the recorded temperature in winter was under 18 degrees,
which is below the World Health Organization’s minimum healthy indoor temperature.”
Lower recorded temperatures were also associated with other signs of cold. For people living in homes where the recorded
temperature was lower than 16oC, 45 percent said they could see their breath inside during winter, and 36 percent rated
their house as always or often cold.
“If the indoor temperature is 16 degrees or less, some people may need at least two or three layers of clothing, adding
a singlet or a jersey to keep warm, if not both,” Dr Bretherton said.
“That’s especially so for the very young and very old.”
People living in houses they didn’t own, and those who said they didn’t have enough money for everyday needs, also
experienced colder indoor temperatures in winter (with mean recorded temperatures of 18.1 and 17.7oC, respectively).
Houses with efficient heat sources such as wood burners and heat pumps recorded warmer average temperatures in winter
than houses with electric heaters, or where people did not heat regularly.
Household expenditure data from the Household Economic Survey 2015/16 showed more than one-quarter of New Zealand
households had at least one indicator of energy hardship – such as struggling to pay utility bills on time, having cold, damp, or mouldy housing, or paying more than twice the
median for energy costs as a proportion of household income. At the extreme end, around 1 in 4 low-income households
paid more than 10 percent of their income on household energy costs.
Why did Stats NZ want to do this?
In New Zealand, houses are not always at safe and comfortable temperatures, but the extent of this problem is not known.
Measuring temperatures in homes selected for the GSS allowed Stats NZ to do this across many different groups. He Kainga
Oranga, University of Otago’s Housing and Health Research Programme, supplied the thermometers and gave advice on the
process.
Notes about the survey
Stats NZ asked GSS respondents for permission to take the temperature inside their homes. This was voluntary – people
did not have to agree. Permission was asked only when the interview took place in a person’s home, with 93 percent of
eligible people agreeing.
Temperatures were taken in the room where the interview took place, so the results are a snapshot of the temperature at
the time of the interview. Most interviews took place between late morning and late afternoon, with the mean time for
the start of the personal interview at 2:19pm.
For more information about these statistics:
ends