Survey highlights need for improvement in insulation and winter household heating habits
Results in the latest report on the BRANZ House Condition Survey
show around half of New Zealand houses still lack adequate insulation and under-heat their home in winter.
The survey of 560 dwellings, undertaken in 2015-16, found 47% of houses had ceiling insulation below 120mm, the level
recommended by the Energy Efficiency and Conservation Authority. The report also draws attention to householder heating
Results from the survey have found whilst living areas are typically heated at some time in winter, almost half of
households did not usually heat bedrooms at all. This included bedrooms occupied by children under 18 years old. The
World Health Organisation (WHO) recommends indoor temperature of at least 18oC in occupied areas of the house or higher
for vulnerable groups like young children, elderly or those living with illness. Unheated rooms in winter are unlikely
to consistently achieve this WHO recommended minimum for a healthy indoor environment.
The roof can be a major source of heat loss from the home, but is also one of the easiest areas of the house to
insulate. The Survey found one-third of houses have an effective heating system but have suboptimal insulation in the
roof space, so will be losing a lot of this heat to the outside.
BRANZ researcher Vicki White said insulation and heating are essential for maintaining a warm, dry home and ensuring a
healthy environment for household occupants, particularly in the colder months.
“Home owners and landlords should consider improving insulation in the roof space to get the most from their heating.
Insulation is cost-effective in the long-run. Heating a well-insulated room is far more economical as it will retain the
“Houses kept warm and dry with good levels of insulation, good ventilation systems such as extractor fans and regularly
opened windows and doors will help reduce the risk of damp and mould.”
Completed every five years since 1994, the BRANZ House Condition Survey is the largest survey of its kind in New
Zealand. Monitoring housing condition through an onsite property assessment, the survey provides a comprehensive picture
of the state of houses and the general conditions people are living in. The 2015 House Condition Survey was funded by
the Building Research Levy, the Ministry of Business Innovation and Employment and the Energy Efficiency and
Notes about the survey:
• Previous surveys were conducted in 2010, 2005, 1999 and 1994.
• The 2015 survey randomly selected homes across 13 areas of New Zealand including urban and rural, owner-occupied
and rental properties. Rental properties featured as part of the survey for the first time in 2010.
• There were 560 dwellings surveyed in 2015-16. The sampling frame was designed to capture a representative sample
of owned and rented houses.
• There will be a number of underlying factors and drivers affecting the trends presented in the report including
materials, property age, location, occupant characteristics and repair and maintenance activity. This report looks at
just a few of those variables and BRANZ recognises further analysis would be of benefit.