Self-Build: Underfloor Heating

Underfloor heating not only gives you a warm glow, it also saves on heating bills, says Graham Norwood

Self-builders already know the advantages of creating their own homes over buying mass-produced ones. But if any one feature demonstrates the customised stylishness and efficiency available in a self-build, it must be underfloor heating (UFH).

Although it dates back to Roman times, when heated water was passed through and between flag stones, the concept of UFH has taken a while to become popular in the UK. It now exists in about 20 per cent of new builds, according to surveyors, but is still rare in all but a few properties built by professional developers.

Underfloor heating works in a similar way to that of conventional heating. Warmth, generated by water or electricity, passes through pipes but instead of them leading to a series of wall-hung radiators, they are installed into the fabric of the floors. Each room on each storey of a home could have a separate set of pipes with controls and a thermostat; the warmth then transfers from the pipes directly into the atmosphere of a room.

UFH has become popular with self-builders because they can include it in the most cost-efficient and space-efficient fashion when building from scratch or converting. But even "retro-fitting" it to a built room is possible, and the placing of piping on an existing floor and putting a tiled surface above it will lift the level of the eventual floor by only 20 millimetres or so.

If you are considering installing UFH, you have two main choices. The first is the warm water system. It uses flexible pipes looped under the floor and connected via a manifold to an existing radiator or boiler. Any kind of fuel can be used to heat the water, through conventional oil, gas and solid fuel to more exotic forms, such as solar panels or Agas. Many experts recommend a condensing boiler because it is at its most fuel- and cost-efficient when working at relatively low temperatures. Underfloor pipes depend on long-duration heating between 35 and 50 degrees centigrade.

The second type is electric underfloor heating. This usually takes the form of thin "heat mats" installed under the floors and connected to a power supply, again with a simple thermostat in each room. These mats are generally easier to install than piping and can be glued beneath floor tiles in many circumstances. A cabled electric underfloor heating systems is also being developed, with the cables sometimes sitting in joists under tongue-and-groove flooring in new properties, or in specially created floorboards with recesses underneath to house the cables.

Whichever system you prefer, there are clear benefits to underfloor heating beyond the aesthetic one of leaving walls uncluttered by radiators.

"Underfloor heating warms the room from the floor up, meaning people feel its effect quickly. It's about 30 per cent cheaper to run than radiators, the modern pipes are virtually maintenance free, and the heat produced is "radiated" rather than "convected" which gives more uniformity to the warmth across a space," says a spokeswoman for Continental UFH, one of the UK's largest suppliers and installers of underfloor heating. "There's a hygiene reason too. There's usually a lower moisture level associated with the warmth generated by underfloor heating compared to traditional heating, which reduces the numbers of house mites in a property," she says. UFH systems tend to raise relative humidity more than traditional radiators, too, giving a healthier environment.

But cost remains perhaps the most persuasive argument for UFH. Mike and Shirley Guthrey fitted it throughout the three-bedroom bungalow they completed last year just outside Mansfield in Nottinghamshire. "It cost roughly £17 per square metre to install and after six months of bills, it appears to be slightly less expensive to run than we believe a conventional radiator system would have cost," says Mike.

There can be downsides to UFH, aside from the disruption it causes a built property when being retro-fitted. Comparisons with normal radiator heating suggest the heat-up period is about 20 per cent longer for most UFH systems, and a commensurately longer cool-down period. It therefore cannot respond quickly to people entering a cold house or someone simply feeling chilly and wanting a rapid blast of heat.

There is also one other problem – relatively few plumbers are familiar with it, making it more important than ever to get experts in to install and repair it if something goes wrong. There are hundreds of firms that specialise in UHF, but as always it is essential to check the experience and skills of a firm before entering into a contract.

One way to check is at the underfloor Heating Manufacturers' Association: membership means a firm abides by a code of professional conduct, which suggests the best materials to be used and the training required for installers. Members also agree to share expertise within the industry. Lists of member companies are on its website, www.uhma.org.uk.

Hot topic

Self-evidently the underfloor heating option must be chosen at an early stage of a self-build project to ensure the selected flooring is most effective.

For those creating a building from scratch, hardwood can be used to cover floors but experts advise that the sections or planks should initially be laid "loose" – without being nailed or glued into place – to allow it to acclimatise to the heat from the pipes beneath. A concrete screed surface is also considered very energy-efficient because it tends to diffuse heat relatively evenly instead of allowing it to concentrate where pipes are closest to the floor.

If you are converting a building where there are suspended timber floors with too little space to install pipes on top of joists, you can locate the pipes between the joists instead. The individual or installation company will require more time to build small "shelves" or to slice out sections of the joists.

Self-Build ABC, an advice centre, suggests that carpet and underlay should not have a combined tog rating of more than 1.5, because carpets act as an insulator and will slightly reduce the output of heat from the floor.