last updated 20th January 06
by Steve McCall, managing director, DEVI Electroheat

Whole house heating or specific areas

Not since the Romans brought the hypocaust to Britain has underfloor heating enjoyed such popularity. Indeed it is rapidly becoming the "must have" heating option for users who realise that, as well having the virtues of being a simple, efficient and comfortable heat source, it avoids the need for unsightly wall hung radiators.

While the Romans relied on the circulation of warm air beneath the floor, the two main underfloor heating options available today are wet and electric systems. Both have pros and cons and can be used for whole house heating or for certain areas, such as in kitchens and bathrooms, and are effective beneath ceramic tiles, timber, carpet, vinyl and linoleum.

Wet systems, using pipes linked to a central heating boiler, have flourished particularly in more adventurous "builds" where they are installed as part of the plumbing process. A disadvantage is that skill is needed to achieve a satisfactory installation and creating a finished floor involves an overlap of different trades which adds to the time and cost.

Electric underfloor heating systems have the advantages of needing a far lower skill base to install and of being suitable for installation in all types of floor, whether they are new concrete floors, renovated bathroom floors or new or renovated wooden floors. A key benefit of electric systems is that they are thin so the complete installation takes up as little as 10 to 15 mm floor height including the new floor covering.

Two systems of electric underfloor heating are available: cable and foil. Foil systems offer the bonus of being the thinner of the two but are less flexible since the foil sheets are available in either square or rectangular format and cannot be cut to awkward shapes which are common place.

Cable and innovative cable mat systems, which are designed to speed up installation, may be bent and cut to fit around items such as lavatories and can accommodate odd room sizes, thus avoiding any cold spots. Fault finding is also relatively easy and, with some systems, it is possible to isolate a break in the cable to within a 20mm x 20mm tile area and repair it effectively.

While cable systems are generally laid into concrete and used predominantly in new build situations, cable mats are easily laid on top of existing subfloors, offer convenience and speed during installation, and may act as either simple floor warmers or whole room heating solutions. In all cases control is by electronic thermostats, thus conserving energy, minimising running costs and providing the user with exactly the required temperature.

Depending on site conditions and the heat output required, up to 10m of mat can be laid in 30 to 60 minutes. The ease with which electric systems can be fitted means that the work need not involve other trades, except for a qualified electrician who simply connects the supply and thermostat on completion of the job.

Estimating for the final floor covering and cable heating mats can go hand-in-hand since, by making a sketch and measuring the room, it is relatively simple to calculate the quantity of mats required and their position on the floor.

When it comes to installation there is no need for complicated marking-out. The floor is cleaned thoroughly prior to laying out the self-adhesive cable mats which are positioned as required. Depending on the new floor surface, they may then be encapsulated using self-levelling screed or be covered with a thin layer of tile adhesive; the final floor covering can then be laid on top.

Good quality cable and mat products should carry a warranty of at least 10 years but there is no reason why they should not last the lifetime of the building. Failures are rare and faults, should they occur, are, as a rule, caused by mechanical damage, like a nail or drilling.

Some system suppliers are happy to partner installers and offer full training either on site or at specialist training centres. This has real benefits for all those installing electric cables or cable mats as it not only ensures that the products are fitted correctly but will also speed installation times and enable a complete package to be offered to the end user, thus maximise profitability.

Further infromation www.devi.co.uk.