Home Insulation Buying Guide

The government's home insulation bungle has demonstrated the importance of knowing what's what.
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02.Insulation products

Glasswool and rockwool batts and blankets
Natural wool
Cellulose fibre
Boards (extruded polystyrene or expanded polystyrene)
Reflective foils

Glasswool and rockwool batts and blankets

Glasswool is made largely from recycled glass. The Insulation Council of Australia and New Zealand (ICANZ) says its glasswool is 80% recycled waste glass, and its rockwool about 30-40% recycled building and slag waste.

Batts are inexpensive, easy to cut and fire-resistant. You can install them yourself, but make sure they don’t get compressed or wet, as this will reduce their R-value (thermal resistance).

You also need to check they’re butted together firmly when installed, as gaps will dramatically lower their effectiveness.

Rockwool is denser than glasswool and a better sound absorber, so this may be a good choice if you’re looking to reduce noise. However, it’s generally more expensive than glasswool.

No evidence for health scare

The International Agency for Research on Cancer (IARC) has now confirmed there is no evidence to support previous concerns that these products were possibly carcinogenic in a similar way to asbestos: minute particles becoming lodged in the lungs.

Manufacturers also now produce glasswool and rockwool that are more bio-soluble than before, meaning that if you do happen to inhale some fibres, they leave the body more quickly. You’ll still need to wear protective clothing to install these products though, to avoid skin and respiratory irritation (see DIY).

Natural wool

Natural wool is sold as batts, blankets or loose fill. Experts say wool is a niche product in Australia although it’s more popular overseas. Batts are usually wool blended with polyester, which helps them keep their shape. It’s recommended you choose batts that are 70% wool as these are more likely to be fireproof.

In CHOICE tests in 1997, some wool batts failed fire-resistance tests, so ask for assurance that it’s been adequately tested, preferably to the more stringent British Standard 5803 part 4. Also check the insulation has been treated to permanently resist insects that can breed in unprotected wool insulation.

Wool is usually more expensive than other insulation. If used as a loose fill it must be thoroughly scoured and treated with insect repellent and fire retardant.

Cellulose fibre

Cellulose fibre is made from pulverised recycled paper, and is a loose fill that must be installed professionally. It can only be used in roof and ceiling spaces, and is a good option if your roof space is difficult to access.

Cellulose fibre can be dusty, so you need to put in barriers to prevent it falling down through exhaust fans, vents and the like. Some manufacturers spray it in with a sealer. Cellulose fibre is treated with borax and boric acid to make it fire and insect-proof.

The other issue with cellulose fibre is settling. According to the Australian standard, the R-value any insulation product claims should be the one it achieves in the long term, so a reputable installer will quote the R-value of the product when it has settled. (See Don’t get ripped off)

Boards (extruded polystyrene or expanded polystyrene)

Extruded polystyrene keeps the air in and water out, while expanded polystyrene isn’t water-resistant. Boards are useful especially if space is limited. They have to be installed between non-combustible surfaces, such as plasterboard, reflective foil or brickwork.


Polyester fibres (including recycled PET bottles, such as soft-drink bottles) can also be made into batts and blankets. Polyester is a good choice if you’re insulating a space you’ll go into occasionally, such as an attic, as it doesn’t create extra dust or have loose fibres. It also doesn’t cause any irritation during installation.

Reflective foils

Reflective foil insulationFoil can cut out 95% of radiant heat, so it’s a particularly good material for keeping a house cool in summer or in a climate that’s hot much of the year. Reflective foil can be installed under the floor, in the roof construction or the walls of a house.

It’s possible to install silver batts yourself, but keep in mind there needs to be a still air space of at least 25 mm below the foil in order for it to be effective. Foil sarking also provides a condensation barrier and can act as a ‘second skin’ under tiles, protecting ceilings and walls from leaks and cracks.

Make sure there are no tears in foils — they decrease its performance as a vapour barrier. Surface dust can also decrease the foil’s R-value, which is why it must always be installed with the reflective surface facing downwards. See Table 1 for where the different insulation products would typically be used.


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