How to install insulation into weatherboard walls

During your renovation is the perfect time to replace any worn or rotting timbers, or internal wall linings in your home. This will allow you to install wall insulation into your weatherboard walls to make your renovated home more comfortable.

Weatherboard walls contain a simple timber frame and external weatherboard cladding. Weatherboard walls have a lot of room for energy efficiency improvements, as most weatherboard houses constructed prior to 1990 are likely to have uninsulated walls.

Weatherboard house

Step 1: Select the right insulation

If you are removing the internal lining of your walls, there are a range of insulation batts that may be suitable for your wall insulation, including polyester, glass wool, rock wool and natural wool. We’ve provided some information for you on how to select the right insulation.

The recommended minimum R value for wall insulation is R1.5. Going above the minimum standards to R2.5 will result in greater comfort and energy savings in your renovated home.

Step 2: Installing insulation into weatherboard walls

Ensure that the insulation batts are less than 90mm thick – this way, they will fit snugly within the wall frame. Be careful not to compress the batts as this will reduce their efficiency. The batts should never touch the weatherboards as this could cause condensation build-up over time.

Install insulation into weatherboard walls

If you’re replacing weatherboards, it’s a good idea to wrap the building in a layer of builder’s paper or house wrap. You can also consider adding a layer of reflective foil over the insulation to reduce condensation build-up.

If you are not planning to remove any wall lining, specially treated loose-fill insulation can also be pumped into the wall lining’s cavity. This could be installed by drilling holes into the plasterboard from the inside, or drilling holes into the weatherboard from the outside.

Find out more about loose-fill and pump-in insulation in our guide on how to insulate double brick walls.


There are a few key points to consider, other than price, when deciding what type of insulation to install.

  • Energy efficiency of the product : The higher its R value, the better.
  • Size : The chosen product needs to fit in the space available without being compressed.
  • Proximity to electrical wiring : You will often cover electrical wiring while installing insulation, so seek advice from your electrician before commencing work. Ensure that any work undertaken by the electrician does not compromise the quality of the insulation installation.
  • Environmental credentials : Research the insulation product’s environmental qualities, such as toxin levels.
  • Acoustic performance or Sound Transmission Class (STC) rating : Most insulation products will provide a certain level of sound reduction as well as thermal insulation. Good acoustic performance is especially important if you have a problem with external noise. Heavier weight insulation products such as rock wool tend to have the best sound reduction performance for a given width.

Questions to ask

Are you looking to have your insulation installed by your builder or an insulation installer? Installing insulation carries potential risks and requires expert knowledge. Poor installation of insulation will affect its performance and your potential cost savings, so it’s important to ask the right questions of your installers.


Will your installer take the appropriate safety precautions?


Some types of insulation require the use of specialised equipment, such as masks and protective clothing, so electrical and fire safety are particularly important issues. Insulation installation companies should be able to advise you on the appropriate safety precautions for your walls when you obtain a quote.


Will the insulation be correctly installed?


Your builder or installer should ensure that the insulation product supplied is less than 90mm high so that the insulation is not compressed when installed. They should also recommend a type of building paper, house wrap or reflective foil to separate the insulation from the weatherboard, in order to avoid condensation.


Can your installer guarantee good coverage?


Ask the installation company whether all sections of your external walls will be insulated and whether they can guarantee good coverage. Some companies will undertake surveys with infrared cameras before and after installation to check that it has been properly installed, or may provide this service as an optional extra. To be effective, the thermal imaging needs to be undertaken when there is a reasonable temperature difference between the inside and outside of the house – either on a hot summer day or a cold winter day when heating is operating.

More information

Various Australian Standards and National Codes of Practice cover the installation of insulation products. For more information on installing insulation visit the Insulation Council of Australia and New Zealand (ICANZ) website.