Good Repair Guide: Retrofitting wall insulation

Houses built before the late 1970s are unlikely to have any insulation in the walls unless major alterations or renovations have been carried out.

This Good Repair Guide explains options for retrofitting insulation into existing residential timber-framed walls. Insulation materials covered include fibreglass, polyester, wool and mineral wool (and blends of these) and rigid sheets such as polystyrene and PIR/PUR foam.

This guide does not cover blown-in and injected foam insulation or retrofitting insulation to walls where there is no access to the wall framing or solid construction such as concrete block, precast concrete, double-skin brick or solid timber.

The thermal performance requirements of building elements given in this book are from the 4th edition Building Code acceptable solution H1/AS1 and verification method H1/VM1. Note that 5th editions of H1/AS1 and H1/VM1 replaced the 4th edition on 3 November 2022.