Water underfloor heating pumps warm water through pipework below flooring.

Requires: Flooring underlay or carpet of less than 2.5 tog.

Enables: Heat Pumps.

Underfloor heating systems can be used with almost any kind of boiler but are the most efficient system for heat pumps.53 Underfloor heating can be used in conjunction with radiators if some of the building is not converted to underfloor heating.

As well as being more efficient in conjunction with heat pumps, there are other advantages to switching to underfloor heating:

• Underfloor heating covers a much larger surface area than radiators, so can heat a building while running the heating system at a lower temperature spread more evenly, saving money and abating emissions.
• Underfloor heating heats up air just above the floor mostly. In contrast, radiators heat the air above them at ceiling level. This higher space is less in need of the heat which is more likely to dissipate out through ceilings and walls.
• Rooms incur far less hot and cold spots with underfloor heating than radiators. This makes for a more comfortable environment.
• Radiators cause much stronger air currents than underfloor heating. Radiators operate at a much hotter temperature, emitting heat from a much smaller area. This means they move pollen and dust around rooms more. Underfloor heating is comfortable for people with conditions like hay fever and asthma. Underfloor heating can also make a building easier to clean.
• No radiators mean no risk of radiator burns.
• A building can be used more flexibly. Increased wall space because radiators are no longer fitted can provide more room for equipment like desks, cupboards, or bookcases.

When installing underfloor heating, the type of screed is important. Screed is the substance which encloses the pipework and levels the floor. 'Dry' screed is solid and cheaper, while 'wet' screed is a liquid, making it easier to obtain a flat floor. 'Wet' screed can be applied more thinly, which can also be beneficial because installing underfloor heating will raise the floor level by the thickness of the underfloor heating system and screed. The type of pipework may determine which screed is most suitable. Underfloor heating can be used with any type of flooring provided underlay and carpets are below 2.5 tog.

The principal drawback of underfloor heating is its high installation cost, mainly due to the taking up and laying down of flooring, which is also highly disruptive whilst the work is taking place. Underfloor heating is therefore most cost-effective and least disruptive when installed in new builds or extensions. Whether a retrofit or new build, cost effectiveness of underfloor heating installation can be increased by installing Floor Insulation or new flooring at the same time.

Electric underfloor heating systems are also available. These are less costly and disruptive to install but will drastically increase electricity demand and subsequently heating costs.