The primary focus of J3D6 is to ensure that metal-framed walls forming part of the building envelope incorporate thermal breaks. A thermal break is an insulating material designed to reduce thermal conductivity and inhibit the flow of thermal energy between conductive materials. In simple terms, thermal breaks minimise heat transfer and improve the overall thermal performance of a building. These provisions address the localised heat transfer through poor detailing and apply in addition to the thermal bridging mitigation provisions of J3D78.

Specifically, J3D6 mandates that any metal-framed wall must have a thermal break with an R-Value of at least R0.2 at all points of contact between the external cladding and the metal frame. This requirement is applicable when the wall does not have a lining or when the lining is directly affixed to the metal frame. Moreover, J3D6 provision applies to walls clad with weatherboards, fibre-cement, or metal sheeting. Walls constructed using insulated sandwich panels are exempt from these requirements as sandwich panels limit thermal bridging.