Reflective foil insulations are better at reducing radiant heat transfer than conducted heat transfer, and therefore have their best performance in summer. They should be used with a still air space of at least 25 mm for best performance. When installed in a roof space, the insulations have both a summer R-value and a winter R-value. In this case, suppliers should quote an R-value which assumes the top layer of the foil is covered in dust. Reflective foil is not recommended for use in cavity brick walls.

Reflective Foil Laminate (RFL). This insulation consists of two layers of aluminium foil, laminated to a reinforcing membrane of glass fibre. Only flame retardant grades should be used. Australian Standard AS 1903 applies to the manufacture of the foil and AS 1904 applies to its installation

. The RFL is used as both a roof sarking and as a wall insulation, and in some climates is used as a vapour barrier. When used as a wail insulation or roof sarking, one side of the foil is coated with blue dye to prevent eye damage to installers from sun glare.

Foil Batts are formed from two to four layers of reflective foil separated by spacers. As with RFI, Australian Standards AS 1903 and AS 1904 apply to the foil batts.

The foil batts can be laid over ceiling joists and placed between wall studs. It is important that the batts fit firmly together to prevent air movement, otherwise their performance will be degraded. The R-value is dependent on the number of layers of foil, whether or not the top layer will be covered in dust, and whether or not there are adequate air spaces. When used in a roof space, the batts will have a higher summer R-value than their winter R-value, but the winter R-value may not be adequate for use in areas which require winter heating.

INSULATED BUILDING MATERIALS

A range of building materials which have insulating properties are available. This includes Aerated Autoclave Concrete (AAC), insulated panels, and expanded polystyrene forms which are used as a framework for walls.