How much insulation does my home need?
The regulations in the Building Code of Australia (BCA) that apply to home insulation are complicated. As well as determining specific R-value requirements for different parts of a home, they also contain requirements for ventilation, and various other related issues.
For the purpose of insulation regulations, Australia is divided into many different climate zones. Each climate zone has its own particular insulation requirements, and to make things a little more complex, different states and territories also enforce their own particular exceptions to the BCA requirements.
- You can find out more about the different climate zones and download climate zone maps on the ABCB website.
Insulation can also affect other parts of your home like electrics, which creates all sorts of related fire and electrocution hazards. The regulations that exist are as much for safety and the prevention of accidents as they are for energy efficiency.
When you're planning your insulation, you will need to consult an expert to ensure that it complies with the rules for your area.
Which rules specifically apply to insulaton?
For your home's insulation to be properly compliant, the building envelope must be constructed so that it satisfies:
- Part 3.12 of the Building Code of Australia Housing Provisions (BCA)
- AS/NZS 4859.1 – Materials for the thermal insulation of buildings
- The manufacturer’s specifications, to ensure that the product performs as tested
In addition to the BCA, State governments have their own set of regulations to abide by which alter the requirements outlined in the BCA.
What's generally required in Australia?
The first step in meeting regulatory requirements is to determine what climate zone you're in and what type of dwelling you need to insulate. This will determine the R-values required for different parts of your home.
These R-value objectives aren't measured through insulation alone though; the whole construction is measured, taking into account additions to the R-value like the inherent R-value of things like brick walls, as well as subtractions caused by windows or any other thermal bridges that might exist.
This is why it's so crucial to have the insulation labelled clearly and installed exactly to the manufacturer’s specifications and instructions. If you don't, you may find that while on paper you meet the requirements, in reality your actual insulation is nowhere near as effective as what you'd calculated.
Having your thermal envelope independently assessed is important - you may not be able to obtain a construction permit if the building doesn't meet the minimum 'Deemed-To-Satisfy' requirements. Likewise, there's very little point paying for lots of insulation if it's not going to do its job properly!
Required R values for walls, roofs and floors
Below is a table outlining the basic R value requirements for walls, roofs and floors. Note that there are many other requirements and exceptions to these figures, depending on the state, type of home and materials your home uses:
| Climate zone: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | |
|---|---|---|---|---|---|---|---|---|---|
| Roof / Ceilings | |||||||||
| Direction of heat flow | Inwards | Inwards/Outwards | Outwards | ||||||
| Very light coloured roofs (Absorptance ≤ 0.4) | R4.1 | R4.1 | R4.1 | R4.1 | R4.1 | R4.1 | R4.1 | R4.1 | R6.3 |
| Light coloured roofs (0.4 < Absorptance ≤ 0.6) | R4.6 | R4.6 | R4.6 | R4.6 | R4.6 | R4.6 | R4.6 | R4.6 | R6.3 |
| Dark coloured roofs (Absorptance ≥ 0.6) | R5.1 | R5.1 | R5.1 | R5.1 | R5.1 | R5.1 | R5.1 | R5.1 | R6.3 |
| Walls | |||||||||
| Direction of heat flow | Inwards | Outwards | |||||||
| R2.8 | R2.8 | R2.8 | R2.8 | R2.8 | R2.8 | R2.8 | R3.8 | ||
| Floors | |||||||||
| Direction of heat flow | Inwards |
Outwards | |||||||
| R1.5 | R1.0 | R1.5 | R2.25 | R1.0 | R2.25 | R2.25 | R2.75 | R3.25 | |
