Cavity Wall Insulation

Up to 50% of heat loss can be through your walls.

If your home has insulation in the ceiling and well- fitted and sealed insulating window coverings, but lacks wall insulation, over 50% of your heat loss can occur through the walls. So, insulating the walls can make a significant difference to the temperature in your home, and consequently to your comfort and heating/cooling bills.

Where can cavity wall insulation be installed?

If your existing home has double brick or brick veneer walls, there is a cavity between the external brickwork and the internal brickwork/timber frame which can be used to install insulation. However, monocrete walls, wood cavity walls (usually fibro cladded), weatherboard walls, and most other forms of walling either have negligible internal cavities, or cavities that are difficult or dangerous to access to the point where retrofitting cavity wall insulation would be costly or dangerous. In these cases, it is inadvisable to retrofit cavity wall insulation, but insulative cladding (such as polystyrene boards) can be added to the exterior of the walls. A weatherboard wall can also be insulated either by prising off boards to gain access to the gaps between the studs, and then replacing them afterwards, or by drilling holes through the internal walls (through the plaster). The remainder of this fact sheet is focused on installing insulation in double brick/brick veneer walls.

Comfort Level: Installing cavity wall insulation into a brick veneer wall can prevent up to 85% of heat transfer through the wall. For a double brick (sometimes called 'cavity brick' or 'brick cavity') wall, this figure is up to 63%. Either way, your home will be warmer in winter and cooler in summer. Cavity wall insulation will also keep the interior of your walls warmer in winter, virtually eliminating condensation and mould problems. Installing cavity wall insulation in a weatherboard wall can reduce heat losses by up to 75%, although it may be more expensive than the other kinds of walls due to the added difficulty in installation.

Money Saved: By reducing the heat loss/gain through a house's walls, your heating/cooling bills will fall. Savings in energy consumption used for heating of up to 35% are possible when cavity wall insulation is added to a home with existing ceiling insulation (assuming same level of heating before and after). Choosing to lower the thermostat temperature can reap even bigger savings.

Environmentally Friendly: Reducing heat loss/gain will reduce your energy consumption, cutting your greenhouse gas emissions. Insulating the walls of an average Canberra home will save up to IT of greenhouse gases per year.

Improved EER: The Energy Efficiency Rating (EER) of a Canberra home can be increased by 1 or 2 stars by installing cavity wall insulation (depending on the size of the house, the type of wall/floor construction, and the number, size and location of windows). Research shows that higher EERs can command higher prices in the real estate market.

Acoustics: Cavity wall insulation is also an acoustic insulator, protecting your home from unwanted exterior noise and reducing the impact of noise from within the home on your neighbours. This effect is most significant for windowless walls.

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