Description

Around half of all New Zealand houses have no insulation in their walls.

Retrofitting insulation in walls typically involves replacing the interior linings, so retrofits are often done only as part of wider renovations. Linings-on retrofits are possible by blowing insulation into the wall space, but in some cases, there will be no existing wall underlay. This poses a potential risk of water tracking through the insulation towards the inside of the wall, a problem that has been experienced overseas when rolling out widespread retrofits.

BRANZ has developed a proposed evaluation method to provide a level of confidence that this will not happen when retrofitting insulation into timber-framed walls.

Scope

This research includes:

• Loose-fill insulation
• Developing a water management test for New Zealand loose-fill insulation
• Overview of the evaluation method
• Conclusion

There is significant potential to improve the energy efficiency and carbon footprints of our existing housing stock by retrofitting insulation to walls.

Unfortunately, some walls are riskier to retrofit than others, particularly those without an existing underlay that is in good condition. The risk is that the insulation draws water further into the wall to the framing.

BRANZ has developed an evaluation method, based on E2/VM1, to help find approaches that avoid this problem. Testing with this method in a properly accredited facility can give more confidence that retrofitting insulation will not compromise water management in a wall. The method can be used in conjunction with both loosefill and bulk insulation to provide confidence the systems will perform even with no underlay being present.