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  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.

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Insulation only became mandatory nationwide in 1978, although there were regional exceptions, such as Christchurch, where a bylaw made insulation mandatory in 1972.

This Good Reapir 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 
  • solid construction such as coincrete block, precast c oncrete, double-skin brick or solid timber.