Everything you need to know about insulation

Stop the icy fingers of winter – and summer’s heat – from creeping into your living spaces with insulation.

Bunnings magazine, July 2019

Insulation improves energy efficiency

Effective insulation is the best way to improve your home’s energy efficiency. Installed in the roof, above the ceiling, in walls or under the floor, it deters heat loss and heat gain, and can save you up to 40 per cent on your energy bills.

The most common type of insulation is bulk insulation; it works by trapping little pockets of still air within its structure, which resist air flow. Batts are one form of bulk insulation, available in different materials including glass wool, natural wool and polyester. Glass wool is made from spun, recycled glass and used in most wall and ceiling insulation. Rockwool, made from molten, spun minerals or rocks, has a higher melting temperature so is often used in specialised products such as fire-resistant batts.

Can I D.I.Y.?

There are Building Code of Australia regulations for home insulation, which are about safety as well as energy efficiency. Fitting batts is fairly straightforward if you can access the roof cavity, and you’ll need little more than a utility knife to cut the batts, and your protective equipment. Wall insulation can be installed before the plasterboard goes on, but needs professional attention to retrofit.

Buying batts

Before you shop, measure the space, length by width, to estimate the square meterage. You also need to measure the space between rafters or joists. Insulation comes in differing widths, so if you’re installing between framing, choose a width that fits snugly.

Look for low-irritant products with low levels or no added formaldehyde, that are soft and comfortable to handle and deliver the best square-metre coverage per pack. The most important detail to consider is the product’s R-value. “R-value is the measure of how well the insulation resists the transfer of heat from one space to another,” explains Claire Cunliffe of Earthwool. “The rough rule of thumb is, the warmer your region, the lower the R-value you need. So in areas on the east coast with warm summers and mild winters you’d look at R-3.0 or R-4.0, while in cooler regions you’d want at least R-5.0.”

In a hot climate, however, where you’re trying to insulate against heat gain, you may go higher than the typical level. “If in doubt, the higher the R-value the better!” says Claire.

Fitting tips

Before entering the roof space or underfloor, turn off the power. “Wait for a cool day or start first thing in the morning and take breaks if it gets too warm,” advises Claire. Fluff out the batts to maximise the air trapped in the fibres.

Start at the furthest point and work back towards your entry point. Cut the batts slightly larger than the gap so they fit snugly. Take particular care when cutting that you are clear of power cables and be aware of these while working. Trim batts so there is the recommended space around light fittings that protrude into the roof, or use collars to keep them separate from the insulation, to avoid igniting combustible materials.

Pro tip: Although modern insulation products are low irritant, it’s still wise to wear long sleeves and trousers, gloves, a dust mask and safety glasses.


Photo credit: Getty Images

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Health & Safety

Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page. You can also use a simple test kit from Bunnings to indicate the presence of lead-based paint.
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