Passive Design

Insulation

Passive design must include insulation to reduce heat loss or gain through the building envelope.

Insulation acts as a barrier to heat flow, reducing heat loss in winter to keep the house warm or reducing heat gain in summer to keep the house cool. Inadequate insulation and air leakage are the main causes of heat loss in homes.

The most economical time to install insulation is during construction. Retrospective installation may be more difficult and costly. However, there are options for improving insulation in existing homes.

Insulation is needed in the ceiling, walls and floor. The key choices to be made are:

• the insulation format (blanket, rigid or loose fill) and material (for example, glass-fibre, wool, polyester) used in each part of the building, and
• the amount specified to achieve the desired R-value (that is, the desired level of thermal resistance).

The format and material specified will depend on client preference, the type of construction (for example, timber frame or concrete), and on which part of the building envelope is being insulated.

When specifying insulation materials, the key consideration is the thermal performance of the material over the life of the building. Also consider the sustainability of the insulation material – for example, the emissions associated with its manufacture. For details, see our insulation materials factsheet(PDF) and the materials section of this site. Some thermal insulation products have qualified for the Environmental Choice New Zealand label

Also see glazing and glazing performance for information about thermal insulation in windows and glazed doors.

A law passed in May 2016 makes insulation a legal requirement in rental properties. The requirement will apply from 1 July 2019 for private rental properties. The general rule requires ceiling insulation of R 2.9 for properties in zone 1 or 2, and R 3.3 for properties in zone 3. Ground floor suspended floors must have insulation of at least R 1.3. (There are special rules for ceiling insulation originally installed before 1 July 2016.)

It has been a requirement since 1 July 2016 for landlords to disclose in new tenancy agreements the extent of insulation in their rental properties.

Separate changes to the Residential Tenancies Act also require rental property owners to guarantee that for any new tenancy from 1 July 2019, the home will be warm and dry.

Regulations will be drawn up that set out “healthy homes standards” for rental housing quality. There will be public consultation around this. These standards may cover such things as: 

• indoor temperatures
• moisture or humidity levels
• heating
• insulation
• ventilation
• draught stopping
• drainage.

All residential tenancies must comply with the regulations within five years. Grants up to $2000 will be available for eligible landlords to make the required improvements to their rental homes.

^{Updated: 15 January 2018}