In-slab heating systems are hot water pipes or electric wires or mats that are laid either in a concrete slab or in the concrete topping to a slab and provide heating to living spaces.
In-slab heating systems do not include systems laid over a slab (under tiles or carpet.)
Suspended concrete slabs above a subfloor (not above a habitable room or another dwelling) with an in-slab heating system require under-slab and slab-edge insulation. This is to reduce loss of heat from the heated slab.
Concrete slab-on-ground floors with an in-slab heating system require slab-edge insulation only.
Note: The insulation must be installed in accordance with the relevant provisions and Australian Standards specified in the NSW additions to the Building Code of Australia (BCA).
Generally, solid polystyrene board type insulation is used to insulate slabs, as shown in the diagram below. Insulation suppliers can provide installation and construction information.