This is the most common warm water underfloor heating system installed in New Zealand because it is the most cost-effective to install in a standard home with a concrete floor slab.
Due to existing homes already having a slab in place, this method is only possible in new homes or during extensive renovations. In this method, the underfloor heating pipework is tied to the reinforcing mesh in the construction slab and allows for a quick installation.
Although the heating system installer will install the pipes in the floor, the Kiwi Inslab method requires special considerations from the builder as well. The builder will need to supply and install polystyrene underneath the slab and mark out the locations of the walls on the polystyrene.
RibRaft and other pod floors have polystyrene insulation as part of their construction, so the builder does not have to allow for polystyrene when these floors are used. The engineer may specify a thicker concrete slab, sometimes an extra 25mm thick, to accommodate the pipes. Although these systems work very well, around 10-15% of the heat can leak from the slab edge and through the foundations. There are methods of insulating against this, but there is a general reluctance in the construction industry to implement them due to time and cost restrictions.
A typical Kiwi Inslab system will provide heating to the room in around eight hours and is generally left on low continuously.