Ensuring Compliance for Under Slab Insulation: A Specifier’s Guide

Following changes to AS5637.1:2015 Determination of fire hazard properties: Wall and ceiling linings in the updated National Construction Code (NCC) of 2016, specifiers should look out for non-compliant insulation stock that may still be in circulation.

Background to Changes to the NCC

Insulation products must comply with the Group Number as determined by AS5637.1, which requires product testing in accordance with the AS ISO 9705 standard full room fire test with the material on the ceiling and three walls of the test room. Previously, some insulation products were only tested in their intended applications (e.g. ceiling applications for soffit insulation).

As of May 2019, it is non-compliant to supply products into a soffit insulation application without the appropriate Group Number as determined by the updated standard.

The AS ISO 9705 test involves a propane burner emitting a heat output of 100 kw for 10 minutes, and 300 kw for an additional 10 minutes. The test also analyses combustion gases and smoke production. To achieve a Group 1 rating, the material must not reach flashover during the test.

Avoiding Non-compliant Products

Specifying Group 1 insulation products wherever possible is the most efficient path to compliance. Such products offer the highest-rated fire performance in the widest range of applications, which can save lives in a fire emergency.

Specifiers should validate any product performance claims and ensure testing has been carried out by an accredited laboratory.

Rigid Glasswool Board For Under (Suspended) Slab Soffit Applications

Rigid glasswool board is ideal for under (suspended) slab applications as it achieves a Group 1 rating in accordance with AS5637.1 and is non-combustible. It also offers the following benefits:

• lightweight and flexible;

• excellent thermal resistance

(reduces energy costs);

• excellent acoustic performance; and

• sustainable (made predominantly of recycled materials).

Fletcher Insulation

With over 90 years’ experience in insulation technology, Fletcher Insulation provides high performance thermal and acoustic insulation solutions to the Australian architecture industry. The company’s Pink Thermal Slab is an under slab soffit insulation solution manufactured from up to 80% recycled content. This rigid glasswool board product is ideal for commercial under slab soffit applications where thermal properties are pivotal and provides excellent fire performance, achieving Group 1 fire classification.