Compliance with the law

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Complying with the Building Act

Retrofitting insulation into the external walls of an existing building is ‘building work’ and is required by Section 17 of the Building Act to comply with the Building Code.

It is an alteration to an existing building and must also comply with either section 42A(2)(b) or section 112(1)(b) of the Building Act (depending on whether the work is carried out under a building consent or under a specific exemption from a TA (see previous section). Under these sections, alterations work must not reduce the extent to which the existing building meets the Building Code performance criteria.

Additionally, when carried out under a building consent, section 112(1)(a) of the Building Act requires the entire building’s means of escape from fire to be upgraded to comply, as nearly as is reasonably practicable, with the Building Code. For certain buildings, accessibility needs to be similarly upgraded.

It is important to distinguish between the need -

• for new building work such as retrofitting insulation to comply with the Building Code (as required by section 17 of the Building Act), and
• for the existing building, after completion of the alteration, to not have had any aspect of its Building Code compliance reduced as a result of the building work (required by section 42A(2)(b) and section 112(1)(b) of the Building Act), and
• for the existing building, after completion of the alteration, to comply as nearly as is reasonably practicable with the means of escape requirements of the Building Code, and with the accessibility requirements where these are applicable, if the work is carried out under a building consent (as required by section 112(1)(a) of the Building Act).

These three requirements relate to different parts of the building (new part/s versus existing parts). The extent of Building Code compliance needed is different for each requirement, and the Building Code performance criteria relevant to each requirement can be different.

Complying with the Building Code

When buildings, or parts of buildings, are constructed or altered, the new building work must meet the

Building Code performance criteria. This includes when:

• retrofitted insulation material is installed in wall cavities, and
• there is associated building work, such as repairing cracks in claddings, fixing holes that have been drilled and reinstating linings or claddings.

When an existing building is altered, the overall building (including the wall assembly being retrofitted) must continue to comply with relevant Building Code performance criteria to (at least) the same extent as before. These performance criteria may or may not be the same as those relating to the new building work of the alteration (insulation retrofitting) work. Additionally, the overall building must also be upgraded to comply as nearly as reasonably as practicable, with the Building Code performance criteria for means of escape from fire, and, where relevant to the building use, for accessibility.

The Building Code performance criteria relevant to the new retrofitting work, and the performance criteria relevant to the existing building, are analysed in sections 6 and 7.

How to show the work complies with the Building Code

There are no acceptable solutions or verification methods specifically for retrofitting insulation into wall cavities. However, acceptable solutions for new builds may provide useful benchmarks when deciding if relevant performance criteria are met.

Acceptable Solutions and Verification Methods.

Decisions on the Building Code compliance of retrofitting wall insulation and the effects of the retrofit on the existing building can be complex.

New building work – Building Code performance requirements for retrofitting insulation highlights relevant factors to consider when deciding whether insulation retrofit work complies with the Building Code.

Existing building compliance level after retrofitting insulation highlights relevant factors to consider when assessing the extent of compliance of an existing building after an alteration.

Several different approaches may be used to support claims that building work, or an altered building, complies with the Building Code (whether in full, to the same extent as before, or as nearly as is reasonably practicable). These include relevant Determinations, compliance with Standards, test results, expert opinion, appraisals or in-service history.