Home insulation and heating improvement needed


insulationAround half of New Zealand houses still lack adequate insulation and are under-heated in winter, according to the latest BRANZ House Condition Survey.

The survey of 560 dwellings undertaken in 2015-16 found 47 per cent 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 habits.

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.

Healthy heat

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 says 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,” she believes.


“Insulation is cost-effective in the long run.

“Heating a well-insulated room is far more economical as it will retain the heat.”

“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 Conservation Authority.

The 2015 survey randomly selected homes across 13 areas of New Zealand including urban and rural, owner-occupied and rental properties.

BRANZ admits 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 looked at just a few of those variables and BRANZ recognises further analysis would be of benefit.