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COPYRIGHT 2006 Australian Consumers' Association
Despairing about your over-the-top energy bills or another winter huddled next to a bar heater? It's time to consider insulation. When properly installed, it not only helps keep your home a comfortable temperature all year round, but can also save you money on heating and cooling costs, and should therefore pay for itself over a relatively short period of time.
By using less electricity and gas, you'll also cut down on harmful greenhouse emissions. Some insulation can even provide soundproofing, while other types can help prevent condensation.
HOW IT WORKS
Heat always travels towards cooler areas. Insulation works by reducing the amount of heat entering from outside your home when it's hot, and trapping warmth inside when it's cold outside.
Hear is transferred in three ways:
* Conduction is the direct transfer of heat through solid materials. A metal poker put into a fire is heated through conduction.
* Convection involves the transport of heat via the movement of gases or liquids. You'll feel convection taking place in a two-storey house--the heat rises from the lower floor to the top.
* Radiation is the transfer of heat across space from a warm body to a cold one--an example is the heat emitted by a bar radiator.
Insulation materials work by affecting some or all of the above three ways of heat transfer. The highest percentage of heat transfer occurs via the roof and ceiling, so it's most important to insulate here.
MATERIALS
Insulation can be grouped into three categories: bulk, reflective and composite, which combines reflective and bulk materials.
* Bulk insulation contains fibres that trap tiny pockets of air, which resist heat flow because these air pockets are poor conductors. Types of bulk insulation available are glasswool (fibreglass), rockwool, natural wool (often mixed with polyester) and polyester, all of which come as batts or blankets. Polystyrene boards may also be used as insulation, mainly in walls and cathedral (sloping/raked) ceilings.
Another type of bulk insulation is loose fill. It's made of shredded or granulated material that's pumped into the ceiling space by a machine. Some examples are cellulose fibre (made from recycled paper), natural wool and granulated rockwool.
* Reflective insulation dramatically reduces infrared radiant heat transfer from a hot surface to a cooler one. Reflective insulation is available as foil sheets laminated onto paper, concertina-style foil or as a multi-cell foil product (silver batts)--a structure made of two to four layers of foil with air spaces in between. To reflect heat, foil insulation needs to face an air space of at least 25 mm.
* Composite materials combine elements of the two other types. These include batts or blankets with foil backing (foil side facing out) and foil-faced boards.
While manufacturers of each type tend to talk up their product, experts say any insulation is preferable to none, and every material has its place. The product chosen usually depends on personal issues, such as price, whether it's made from recycled material, where the insulation is being installed, or even who's doing the installation.
PROS AND CONS
* 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 70% recycled waste glass, and its...
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