13. Thermal insulation

Insulation in a ceiling space

A building consent is not required to insulate an existing building, except for external walls and fire-rated internal walls.

What the law says

Subject to section 42A of the Building Act, Schedule 1 exempts the following from a building consent:

Building work in connection with the installation of thermal insulation in an existing building other than in:

(a) an external wall of the building; or
(b) an internal wall of the building that is a fire separation wall (also known as a firewall).

Guidance on the exemption

This exemption does not cover the installation of thermal insulation in an external wall of a building, as this may have weathertightness implications. Installing insulation in internal walls that provide fire separation is also outside its scope, as this could adversely affect the building’s fire safety properties.

Examples where this exemption could apply

A house is being retrofitted with insulation to the sub-floor and ceiling spaces.
An existing apartment building is being retrofitted with fibreglass insulation to the internal, non fire-rated walls for additional thermal and noise control.

Examples where building consent is required

The external walls to a house are to be injected with expanding insulating foam.
A fire-rated tenancy wall to an apartment is to be retrofitted with thermal insulation.

This information is published by the Ministry of Business, Innovation and Employment’s Chief Executive. It is a general guide only and, if used, does not relieve any person of the obligation to consider any matter to which the information relates according to the circumstances of the particular case. Expert advice may be required in specific circumstances. Where this information relates to assisting people: