GUIDE TO HEATING UNDER CARPET
If the underfloor heating can be designed in conjunction with a newly laid concrete floor a practical solution is to use a cable in screed electric heating system with FLOORHEATPRO heating cables type RFC17 embedded under a minimum 65mm floor screed. This would not be possible on wooden sub-floors.
Alternatively, the following solutions assume the sub-floor is already existing.
Initially, all areas will require insulation directly under the heating in order to ensure the maximum response to temperature change when the heating is energised. The object is to ensure most of the heat is directed upwards. This insulation requirement is additional to any other form of insulation installed in the fabric of the property i.e. beneath the sub-floor
Two solutions are available:
- This involves using the under tile type of heating mat rated at a maximum of 150w/m²
- Firstly, any wooden floor boards will need to be strengthened with a 10mm layer of construction board (cement finished tilebacker board). If you have a chipboard floor that is already level and rigid then a 6mm layer of construction board will be OK.
Floor must be level and rigid before installing the underfloor heating
- All concrete floors should be covered and fitted with 6mm or 10mm thick XPS insulation sheets. Although the thickness is optional, a 6mm thickness would be acceptable in most cases. Alternatively, tilebacker cement finished boards can be used. However, Tilebacker board is normally used to strengthen a wooden floor as well as insulate the sub-floor. When tiling on a concrete sub-floor the floor is already rigid and firm, so the most economical thermal barrier is always with XPS. Again, the choice is optional between XPS and tilebacker board. Both XPS or tilebacker board should be fixed to the sub-floor with flexible tile adhesive.
- Next fit undertile heating mats rated at 150w/m² maximum
- Next stage is very important and it involves applying a MINIMUM layer of 12mm thick flexible levelling compound over the heating mat. This will provide a flat level hard surface on which to install the carpet
- Then install the carpet and ensure the total combined tog rating of the carpet and carpet underlay does not exceed 2.5 tog.
- Install a 6mm layer of LAMFOAM foam insulation
- Then install the foil heating mat system – only approx. 2mm thick
- Then install over the foil mats a Dual Overlay Heat Pak which will add a further 7mm thickness to the overall height – the Dual Overlay is specifically designed for carpet heating
- Then install your carpet and ensure the total combined tog rating of the carpet and underlay does not exceed 2.5 tog