By far the best method for performance of the underfloor heating system. The screed provides good thermal conductivity and reasonable response times. But by far the best benefit of using this floor construction is optimum fuel efficiency.

This technique means that you heat the entire concrete slab, which makes it sluggish to respond in comparison to the slab plus screed technique above. A thicker thermal mass stores a lot more energy and gives off heat for much longer, so is best suited to commercial buildings that will be kept at a constant temperature and not have frequent set-back times. It uses more energy to warm up in the first instance, and is now rarely used in domestic properties.

Used in most upper floors, and contrary to something akin to an urban myth, works perfectly well with underfloor heating. A point to note is that if using a suspended timber ground floor, you must use rigid insulation under the entire surface of the floor to prevent through-draughts carrying your heat away. Glass fibre insulation is not acceptable for ground floor use because of draught penetration, but can be used for upper floors.

This technique is a variation on the slab plus screed method. Some hardwoods may require a fixing, for example if they need to be screwed down or fixed with 'invisible clips', and this method provides a way of incorporating battens into the floor screed.

This technique can be applied when fitting underfloor heating into an existing timber joisted floor, particularly if your door heights and stair landings cannot be altered. Because this technique requires the top of the joists to be notched at random locations you should check with your architect or structural engineer before commencing.