Thermal insulation materials for buildings
R-value specification, materials and labelling for insulation.
Overview
AS/NZS 4859 (Part 1 materials, Part 2 installed performance) governs the way insulation is rated and labelled. The 'R-value' on a batt comes from this standard. NCC 2022 distinguishes between material R-value and installed R-value (the latter accounts for compression, gaps and thermal bridging).
Key Requirements
- Material R-value at standard temperature.
- Labelling with R-value, density and thickness.
- Reflective insulation rated for emittance.
- Adjustments for installation effects.
How it's used in the NCC
Called up by Part 13.2 (building fabric) of the Housing Provisions.
Practical Notes
- Material R-value vs total R-value: NCC works in total R-value, which includes framing thermal bridging — easy to under-spec if you only look at the batt.
- Compressed batts in narrow cavities lose a lot of R — don't squash R3.5 into an R2.5 cavity.
Where to obtain
The full text of AS/NZS 4859 is published by Standards Australia and must be purchased — typical price A$150–400 per part. Always work from the current edition referenced in the NCC, not an older one.