What is it and how does it work?
A high-efficiency gas boiler or a heat pump heats up water and circulates it through the network of pipes laid in the slab. The required operating water temperature for underfloor heating varies approximately between 30°C to 50°C*.
Effectively, this system transforms your floor (slab) into a slow release heat radiator that gently warms the air above, eliminating cold spots. The warm air convects from the floor surface losing approximately 2°C at 2.0 meters above the floor, which makes the system ideal for all ceiling heights.
By using low water temperatures (approx. 45°C) underfloor hydronic heating allows from 12% to 15% further reduction in energy demand when compared with radiators fitted system*. Reduction in energy consumtion can be even higher but depends on the quality of home design and build (higher house Energy Efficiency Rating allows to further lower water temperature in the slab heating system). For the latter reason, underfloor heating works well with renewables, particularly air source Heat Pump.
By choosing underfloor heating we should remember that underfloor heating can be fitted in both concrete and timber suspended floors.
Tiles, stone, polish concrete or similar are generally accepted as the optimum covering. They absorb heat rather than insulate and allow that heat to radiate into the room.
Timber flooring will tend to insulate and reduce efficiency, but thinner profile engineered timber has little noticeable impact on heat output. Solid timber is notoriously tricky with underfloor heating — it needs to be properly acclimatised. We highly recommend asking your supplier for advice.
The Carpet Foundation carried out research in conjunction with the Underfloor Heating Manufacturers Association which shows that some carpets can be used with underfloor heating. The research showed that a carpet and underlay with a thermal resistance of less than 2.5 togs does not have a significant impact on efficiency*.
Ultimately, the efficiency and success of an underfloor heating system will depend on the quality and design. Therefore, choosing a supplier who offers a good design service and aftercare is important. A specialist underfloor heating company is often best placed to achieve this.
If the design is wrong, it is unlikely that the homeowner will know until they have lived in the house for a whole heating season — by which time it’s probably too late.
Finally, if you are choosing to pair underfloor heating with a heat pumps it is a good idea to choose one supply and install company. Both are complex systems and getting the whole heating system to work in perfect harmony can be tricky.
The start-up costs for slab (underfloor) heating are higher, but due to more efficient operation, payback period shortens.