Foil Insulation

What Is Foil Insulation?

Foil insulation is made from one or more layers of plastic or paper substrate with a reflective aluminium foil facing bonded to one or both sides. Unlike bulk insulation, which resists the conductive and convective passage of heat, foil insulation works as a radiant barrier — reflecting radiant heat away rather than absorbing and slowing it.

How Does Foil Insulation Work?

The physics behind foil insulation comes down to two properties: high reflectivity and low emissivity. Aluminium foil reflects the vast majority of radiant heat that strikes it and emits as little as 5% or less of that heat back out the other side. When installed correctly next to an air space, this can reduce radiant heat transfer by up to 97% — a dramatic difference compared to leaving a roof space, wall cavity, or subfloor completely unprotected.

In a typical Australian home, the sun heats the roof, and that heat radiates into the roof space below. From there it warms the air, then the ceiling, and eventually the living space itself. A correctly installed layer of foil insulation intercepts that radiant heat at the roof space stage, well before it ever reaches the rooms below.

Why the Air Gap Is Non-Negotiable

Foil insulation only works if there is a genuine air space on at least one side of the reflective surface. Without that air gap, the product has virtually no insulating value at all. Worse still, if the foil is left in direct contact with another building element — such as framing timber or cladding — it will simply conduct the heat energy straight through to that surface instead of reflecting it. Correct installation, with the reflective face oriented properly and a clear air gap maintained, is what determines whether foil insulation performs as intended or does almost nothing at all.

Types of Foil Insulation We Stock

Roof Sarking and Reflective Wraps

Roof sarking is installed beneath roofing during construction to reduce summer heat gain and lower cooling costs, while also acting as a secondary weather barrier against rain and dust before cladding is complete. Reflective wall wraps serve a similar dual purpose on external walls, combining a protective skin for the building with a genuine radiant heat barrier.

Breather Wall Wrap

Where a building needs to manage moisture as much as heat, a breather wall wrap is often the better choice. These vapour permeable products allow air and moisture to pass through the membrane, helping the building "breathe" and reducing the risk of trapped condensation — particularly important in cooler climates or well-sealed, highly insulated homes.

Rigid Foil-Faced Panels (Foilboard)

For applications needing structural strength as well as reflective performance, rigid foil-faced panels combine a foam core with aluminium foil bonded to both sides. These panels suit walls, floors, and roofs alike, and are valued for their non-itchy, easy-to-cut installation and long-term thermal performance.

Where Foil Insulation Is Used

• Roof space — the single most common application, intercepting radiant heat before it reaches the ceiling
• External walls — combining a weather barrier with radiant heat control
• Underfloor spaces — managing both heat loss and ground moisture
• Sheds and garages — a cost-effective way to moderate temperature in uninsulated structures
• Commercial and industrial buildings — where large roof and wall areas make radiant heat control especially valuable

Additional Benefits Beyond Thermal Performance

• Condensation control — helps manage moisture where metal roofing is prone to dripping in humid or tropical conditions
• Acoustic benefits — dampens noise from rain and wind, contributing to a quieter indoor space
• Construction sequencing — sarking and wall wrap allow internal trades to begin work before external cladding and roofing are finished
• Lightweight and durable — unlike bulk insulation, foil products won't sag, settle, or lose performance over time

Building Code Compliance

Foil and reflective insulation installed in Australian homes needs to meet the relevant thermal performance requirements set out in the National Construction Code. Getting the product, orientation, and air gap right isn't just about performance — it also ensures the installation meets the standards required for compliance sign-off.

Shop Our Foil Insulation Range

We stock a comprehensive range of foil and reflective insulation products from trusted brands, including Sisalation, Foilboard, Kingspan Air-Cell, Knauf Earthwool, and Trade Select by Ametalin — covering sarking, wall wrap, breather membranes, and rigid Foilboard panels across every application and R-value. Get in touch with our team for help selecting the right foil insulation for your project.