The thickness of insulation is measured in ‘R-values’. The thicker the insulation, the larger the R value,
The minimum amount of insulation you need is set by the Building Code of Australia. and differs per climate zone. Click on your state to find out which climate zone you’re home is in.
The following table shows the recommended amount of insulation (in R-values) for each climate zone.
R 4.1 is approximately 20cm in thickness.