Extruded Polystyrene. Foam insulation boards are manufactured from extruded polystyrene to Australian Standard AS 1366.4. Although they are manufactured from self-extinguishing raw materials, they will burn if the surrounding structure is involved in a fire. The boards should be installed between non-combustible surfaces.

The boards are available both in lengths of 1200 mm to 3600 mm, and in widths of 425 mm or 575 mm wide to fit between standard timber framing centres of walls or ceilings. The material can be cut with a sharp knife to suit non-standard spacings.

Insulation boards made from extruded polystyrene have a high R-value per unit thickness. This makes them a good choice in applications where space is limited, such as in cavity brick walls, and cathedral ceilings.

Expanded Polystyrene. Foam insulation boards are manufactured from polystyrene beads to Australian Standard AS 1366.3. These boards have similar properties to the extruded foam boards, however they are not water proof and they have less R-value per unit thickness.

There is no Australian Standard for the manufacture of the polyester batts, but they must comply with the fire test AS 1530.3. The polyester insulation is non-toxic, non-allergenic and has no known physical or health hazards.

Spray-In Foams. Chemical foams, such as polyurethane and urea formaldehyde, can be sprayed into wall cavities, and onto an external surface. They can also be used in a ceiling, where they are generally sprayed between layers of a reflective film. The liquid foaming mixture expands into a solid foam layer as it sets.

A number of problems can be experienced when using spray on foam insulation:

1. Toxic gases can be released during application and out-gassing of these gases can occur over the life of the insulation

2. Some foams degrade over time and contract and crumble

3. Spray in foams can cause problems with electrical wiring and switch plates in walls, and their use may contravene the wiring code AS 3000.

There is no Australian Standard for the polyurethane foam, but Australian Standards AS 4073, AS 4074, and AS 4075 apply to the manufacture and installation of urea formaldehyde foams.

LOOSE FILL Insulations

Loose fill insulations are manufactured from shredded or granulated materials that are pumped or blown into a roof space, or sometimes spread by hand.

The loose fill insulations are best for flat ceilings or for ceilings with a slope less than 25 degrees . For more steeply sloping ceilings supporting joists need to be added.

In a flat ceiling, they are generally pumped into a thickness of 100 mm, the level of the beams, and so only one R-value is available. The R-value achieved depends on the density to which the loose fill insulations are installed. If the insulations are 'fluffed up' when they are pumped in, a lower than recommended density can result. In this case, the insulation can settle over time, and the R-value will decrease.

Loose fill insulations are usually installed by a contractor. When obtaining a quote, the customer should specify installation to Australian Standard AS 3999.

This ensures that the electrical wiring will not be incorrectly covered with insulation, and that adequate barriers are used around down lights, exhaust fans, and flues to stop the insulation from coming into contact with these hot objects.

Cellulose Fibre. This insulation is manufactured from recycled paper which is finely shredded and to which a mixture of borax and boracic acid is added to provide fire retardance and vermin resistance. Australian Standard AS 2462 covers the manufacture of cellulose fibre insulation, however it is not a mandatory standard.

A 100 mm thickness of cellulose fibre installed to a density of 40 kg per cubic metre will have an R-value of around R2.6.

Sheep's Wool. This insulation is manufactured from waste wool which is shredded. As with the woollen batts, there is no Australian Standard for the manufacture of loose fill wool insulation. The wool needs to be treated for vermin resistance and rot proofing in the same way as the woollen batts, and similar assurances should be sought from suppliers. The loose fill insulation should not contain recycled fibres or synthetic fibres.

When installed to a density of 20 kg per cubic meter, a 100 mm layer of loose fill wool should have an R-value of around R2.0.

Granulated Rockwool Insulation is made to Australian Standard AS 2461. The insulation may be spread into ceiling spaces by a contractor using a blowing machine, or it may be spread by hand after the bags in which it is supplied have been carried into the ceiling space. If treated with a water repellent the granulated rockwool can be pumped into existing cavity brick and brick veneer walls. If used in an exiting wall, installation should comply with Australian Standard AS 3999. A 100 mm layer of granulated rockwool will have an R-value of around R2.6.