By Penny Day
There are many benefits of underfloor heating (UFH); there are no radiators to spoil the clean lines of a room, space can be saved by freeing up a wall that would otherwise need to be dedicated to a radiator, and floors are warm underfoot.
UFH is also an extremely efficient way to warm a room, and gives a more pleasant heat than radiators, stoves or traditional solid-fuel fires. The entire floor becomes a “radiator” which emits heat in a very gentle way. There are no cold spots and, as most of the heat is concentrated in the lower part of the room, very little is wasted.
Where can it be used?
Underfloor heating is mostly used in ground-floor rooms but, in reality, there is a system to suit any type of floor construction. Wet systems are most easily installed where it’s possible to take up floors or where new floors are being constructed, so is likely to suit new extensions, conservatories and new open-plan kitchen-cum-living areas. Electric UFH is likely to be more suitable for existing rooms as the electrical mesh system is flatter than a wet system so there is less need for floor heights to be altered to accommodate it. There are even electrical mat systems available that can be used under rugs on existing hard floors. On balance, it’s easier to add electric systems to upper-floor rooms.
Types of Underfloor Heating
There are two main UFH systems: hot-water (or wet) systems, and electric mat (or wire) systems. Wet systems basically use warm water from the central heating system. The water is pumped through plastic pipes that are laid on to a sub floor, before the new final surface is installed. Underfloor heating of this type also reduces water-heating costs as it uses water at a lower temperature than standard radiators (about 40°C to 65°C to give a floor temperature of between 23°C and 32°C). Electric systems feature cables which are attached to open-weave mesh mats. There are, however, newer types where the elements are embedded into a continuous roll. The mats or rolls are spread out on the floor, connected together and are then linked up to the thermostat and mains power supply. In general, whilst electric systems are cheaper to install, and cause less disruption to existing floor structure, they are more expensive to run than wet systems, which are more cost efficient.
For your UFH to be most cost and energy efficient, your property needs to be adequately insulated (and preferably adhere to new building regulations). To prevent heat loss, and to ensure that the heat is directed upwards, there needs to be room for insulation to be installed beneath the system.
With wet systems, makes sure you have a space for the controls to be situated (a cupboard will do). Like a radiator, each room heated with UFH has its own valve, but they can all be sited in one spot, along with the timer controls. Most of the plastic water pipes installed in today’s systems are continuous, so there is no danger of leaks as there are no joints – and the system is generally considered to be maintenance-free. Whilst a condensing boiler will offer the greatest potential savings on running costs, any boiler can be used with UFH, as long as it has a sufficient capacity.
The firm fitting the underfloor heating will plan the installation for you. If you plan to add a wet UFH system to an existing room, you will need to seek professional advice. Necessary calculations include the desired temperatures, the ceiling height, the potential heat loss and the type of flooring required.
UFH can be used with almost all types of flooring, even carpet. Research by the Carpet Foundation* has shown that any carpet can be used over underfloor heating without impairing the performance of the system, providing that the carpet and underlay have a thermal resistance of less than 2.5 tog. New indications show that for the majority of carpet styles the thermal resistance will be less than 1 tog.
Stone, Ceramic, Slate and Terracotta
Over the past few years, as these flooring materials have become more fashionable, there has been an increase in the number of homes using UFH. Heat-up time depends on the thickness of the tiles; thick flagstones will take longer to reach optimum temperature, but once this is reached there’s no difference in heat quality between thick or thinner floor surfaces.
UFH is suitable for use with many types of timber flooring, but most installers stipulate that the timber be specifically recommended for UFH use. The flooring should have a top temperature restriction (usually 27°C) and an expansion gap needs to be left around the edges (this is easily hidden by a skirting board or trim). Most reputable manufacturers offer timber suitable for underfloor heating, but always liaise with the flooring supplier and heating installer before making your purchase. Many suppliers will recommend a specific brand of electric UFH and it’s a good idea to listen to their advice.
Vinyls and Laminates
UFH can be used with high-quality vinyls and laminates, such as those from Amtico, Polyflor and Karndean International. Not all laminates or vinyls are compatible with UFH, so it’s a good idea to check with the flooring manufacturer or the heating installer before committing. Many suppliers have developed their own UFH systems, or have one or two that they recommend.
*Research undertaken by the Carpet Foundation in conjunction with the Underfloor Heating Manufacturers Association (UHMA), June 2006