Installing your own underfloor heating

Electric under tile heating

Radiant heat underfloor systems are now available for DIY installation. By heating your floor tiles you gently and economically warm the tiles and all surrounding air creating natural warmth with very little temperature variation compared to the convective heated water created by central heating systems.

Traditional central heating work by heating the air as it passes over the radiators. This convective warmth rises as warm air currents creating a heat differential with the warmest air at ceiling level. This leads to a “hot head/cold feet” scenario and a generally stuffy environment.

Radiant heat is a more efficient and healthy form of heat distribution allowing the air temperature in the room to be set at lower levels resulting in energy savings and as the air circulates less there is less airborne dust increasing comfort levels not only for allergy sufferers but everyone in the room.

Underfloor heating systems are invisible when installed and silent in operation allowing complete flexibility in designing your room layout. There are two popular formats; underfloor heating mats and underfloor heating cables.

The heating mat is a simple to install self adhesive mesh with the heating cables pre-attached. Cables allow more flexibility, which may be necessary in irregular shaped areas, allowing heating to be extended into recesses and also the possibility to vary heat output in different parts of the room by increasing/decreasing cable density..

Heating mats and cables can be installed directly over timber or solid floors and work great under ceramic floor tiles, during installation the underfloor temperature sensor regulates heat via a wall mounted thermostat/timer offering full 24 hour control, 7 days a week with override functions.

Running costs recent developments have lead to the installation of tile backer boards which significantly reduce heat loss into the subfloor and reducing warm up time and energy consumption. Generally a small bathroom would cost around 7p a day to heat to a comfortable temperature, this is however only an approximation and depends on your cost per KwH and any particular heat loss problems.

Heating mats are generally sold in 500mm widths and a range of lengths. It will be necessary for you to sketch out the floor plan of your application, allowing for any floor mounted furniture and fixtures like bath and shower trays. It is important that you establish where the mat will lie and the total length that you will need as this cannot be shortened and any over length piece will have to be replaced.

Installation a groove will have to be cut in the floor to accommodate the temperature sensor and its protective conduit, which should be positioned about 500mm from the wall. The floor should be prepared as normal or tiling, ensure that no sharp protrusions will damage the mat or cable.
Lay the mat down loose without fixing to make sure that it fits and there are no nasty surprises. When rolling out for this test flip the mat over at the end of each run, you can safely cut through the mesh matting being very careful not to cut through the cable (usually red or orange). Turn the mat through 180 degrees and run back alongside the previous run keeping a minimum space of 50mm between cable loops. When satisfied with the layout you can glue the matting to the floor using the integral self adhesive pads. For any awkward areas it is permissible to cut the cable free from the mesh and carefully stick this to the floor with adhesive tape, keeping the loops more or less in pattern.

A hot glue gun will be useful to ensure that any edging pieces without adhesive pads are glued down to prevent lifting.

Now is probably a good time to call in an electrician to test the resistance against the labelled value. Your qualified electrician can now make the connection to the mains supply and install the thermostat (outside the room of course if it is a bathroom). A final test of resistance and continuity should put your mind at rest, before turning off the current and with covering tile adhesive and completing the job, be careful to avoid damaging the cable as you lay the tiles and try to avoid any air gaps or voids between the tiles and the mat.

Finally your installation should be protected by an RCD for safe operation. Do not heat up your system until a suitable time for drying out off the adhesive; consult the manufacturer if you are in doubt.

Underfloor cabling kits are available for loose cable installations, these comprise of a drum of cable, Thermostat Programmer, fixing tape, floor sensor probe and full instructions. With a higher level of skill required perhaps it would be better to use a professional installer for your first loose cable job?