Wall insulation

If you have installed ceiling and underfloor insulation your house will be easier to keep warm, but the largest proportion of heat will now be lost through the uninsulated walls and windows. Wall insulation will help slow some of the heat lost this way.

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How much insulation?

The New Zealand Building Code specifies minimum mandatory insulation standards for new houses. Refer to the section Designing a new home.

Wall insulation should be as thick as the wall cavity without having to squash the insulation to fit it in. Squashing the insulation reduces its effectiveness.

Choose an insulation product with an R-value as high as possible for the thickness of your wall cavity. The R-value is a measurement of insulation's effectiveness - the higher the R-value the better.

You may want to add more insulation than can be fitted into your wall cavities. There are option for doing this, such as lining the inside of your walls with polystyrene insulation and then covering with internal wall board, but EECA recommends you consult with a registered builder about what might work in your house.

Which insulation material?

Wall insulation can be made from polyester, wool, fibreglass and a range of other materials. Not all insulation is created equal though, and some products do have definite drawbacks.

If you are comparing different types of insulation, remember to check:

  • The performance guarantees that the insulation manufacturers offer on their products
  • That the insulation you are looking complies with the AS/NZS 4859.1 Standard. Look for an AS/NZS 4859.1 compliance statement on the insulation packaging
  • The installation instructions for safely installing the insulation, if you are thinking of doing it yourself.

Once you know these things, make sure you are comparing products with similar R-values.

Segments or injected foam?

Segment (biscuit) and injected foam are the most common types of wall insulation.

Segment (biscuit) insulation

Segment, or biscuit insulation, is fitted inside wall cavities. For existing houses, it does require removal of either the wall lining or cladding; however, it means you can inspect the coverage and quality of insulation that goes into your walls.

Injected insulation

In New Zealand the most commonly used type of injected wall insulation is urea formaldehyde foam insulation (UFFI), which is pumped into existing walls as a foam that then dries.

Putting insulation into existing walls usually requires removing the wall cladding or lining. Injecting insulation into walls offers an alternative if you don't want to go to the trouble of removing wall linings.

>> Read more about injected insulation

Take action

It's difficult to insulate walls in existing houses without taking the lining or cladding off. Take the opportunity to insulate when you renovate, and have either the lining on the inside or the outside cladding of external walls removed.

Make sure the outside cladding is in good repair and not leaking, and that there is building paper in the wall. Insulation should not come into contact with outer cladding. This reduces the risk of the insulation getting damp, which would reduce its effectiveness.

Installing wall insulation

Correct installation is critical if wall insulation is to perform properly over its life. Refer to page 30 of the NZ insulation Standard for more details on installing wall insulation.

Download the New Zealand standard on installing insulation, NZS4246:2006.

More information

Seek professional advice

 

From the Resource Centre

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