R-values explained
An insulation product's R-value measures how well it resists heat flow. The total R-value adds up every layer in a roof, wall or floor, including air gaps, and is the best measure of how the whole element performs.
The National Construction Code, and BASIX in NSW, set minimum total R-values for new homes. Roof, ceiling and floor ratings with reflective insulation are given as "up" values for winter heat flow and "down" values for summer.
Australian and American R-values differ
American R-values look much higher because they use different units. Compare products using Australian metric values only.
Types of insulation
| Bulk | Traps still air to resist heat flow. Fibreglass, polyester or wool batts, rolls, loose fill or foam boards. |
|---|---|
| Spray foam | A bulk insulation sprayed on site that also seals cracks and gaps. |
| Reflective | Foil laminated to paper or plastic; reflects heat in the direction the foil faces. Needs an air gap to work. |
| Composite | Bulk and reflective combined, such as foil-faced boards and foil-backed batts. |
Where to insulate first
Ceiling and roof
Usually the easiest to reach and the biggest gain in an existing home.
Underfloor
Worth it for raised timber floors in cooler climates.
Walls
Easiest during renovation or when cladding is replaced; some products can be blown into existing cavities.
Fix thermal bridges
Framing and gaps that bypass insulation leak heat and can cause condensation. Insulation must be installed without gaps or compression.
Installing safely
- Get a licensed electrician to check wiring before insulation is added.
- Keep the required clearances around downlights, transformers, exhaust fans and heaters.
- Use a trained, certified installer; poor installation sharply cuts performance. Work must meet the National Construction Code.
- Pair insulation with shading in summer, or a well-insulated home can hold heat in.
Insulation works with draught sealing and good windows. See draught-proofing, windows and glazing and the cheapest way to heat a home.
Common questions
Insulating the roof, walls and floors could save over 50% on heating and cooling costs, according to energy.gov.au. Savings depend on climate, house and how you heat and cool.
It depends on your climate and construction. The National Construction Code and BASIX in NSW set minimum total R-values for new homes. Ask your installer what suits your climate and construction.
You can, if you can do it safely and follow the manufacturer's instructions, but a licensed electrician should check the wiring first. A trained installer is recommended, especially in existing homes.
Sources
Every rate on this page comes from the regulator or the regulated retailer. Last checked October 2026. Prices include GST unless we say otherwise.