Electric underfloor heating has become much more popular in recent years, and carbon heating film is one of the simplest and quickest systems to fit. This guide explains how carbon underfloor heating film works, where it can and cannot be used, how it is installed and what it costs to run.
What is carbon heating film?
Carbon heating film is a very thin (well under half a millimetre) electric heating element made of carbon strips sealed between layers of polyester film. When it is switched on it warms the floor above it, and the warm floor then gives off gentle radiant (infrared) heat to the people and objects in the room. Because the whole floor surface is warm, there are no hot and cold spots, and the film reaches its working temperature within minutes.
Our standard film is 130 W/m², which suits most rooms. 110 W/m² and 80 W/m² versions are available for well-insulated rooms or for supplementary heating.
Where can it be used?
Carbon film is designed for floating floors: laminate, engineered wood and click vinyl or click eco flooring laid on an underlay. It can also go under carpet if a board overlay system (such as the Flexel ECOMAX-DUO) is laid over the film first.
Typical rooms include living rooms, bedrooms, kitchens and dining areas with floating floors, offices, garden rooms, conservatories and extensions.
Where it should not be used:
- Under tiles, stone or anything glued or screeded down. For tiled floors use an underfloor heating cable mat instead.
- In bathrooms, shower rooms and wet rooms. These are special locations under the wiring regulations; use a heating mat, an aluminium foil mat with the correct controls, or an infrared panel or towel rail instead.
- As a portable heater or anywhere it is not fully covered. The film is a 230 V mains product for concealed installation only.
How is it installed?
- Prepare the subfloor. It must be clean, dry and level. Uneven floors may need levelling compound first.
- Lay the insulation. XPS thermal insulation board should cover the whole floor, with the joins staggered and taped. It stops heat being lost downwards.
- Plan the layout. Keep the film at least 50 mm from the walls and away from fixed furniture and kitchen units. Strips may touch but must never overlap. The film can only be cut at the marked cutting lines.
- Lay the film and tape it in place so it cannot move. Cut small recesses in the insulation for the connections and the floor sensor so they sit flush.
- Make the connections with the correct crimps, insulate every connection and cut end with bitumen tape, and fit the floor sensor.
- Lay the vapour barrier over the film, covering the whole floor and overlapping the joins. It protects the film from moisture and adds a second layer of insulation, which is what makes the installation Class II.
- Connect and test. The film must be connected to its own thermostat with a floor sensor and to a suitable circuit with RCD protection. This part must be done, tested and certified by a qualified electrician in line with BS 7671.
- Lay the floor covering following the flooring manufacturer's instructions for use over underfloor heating.
Many customers lay the film themselves and have an electrician make the final connection. If you would like the whole job done for you, our official installation partner, Standard Electrical Services, can install it.
Running costs and efficiency
Like all electric heating, carbon film turns almost all of the electricity it uses into heat. Running costs depend on the room's insulation, the floor covering, how long the heating is on and your electricity tariff. Because the film heats up quickly and each room has its own programmable thermostat, you only heat the rooms you are using, when you are using them, which keeps costs under control. Running it on renewable electricity also makes it a very low carbon way to heat a room.
Maintenance
Once installed, carbon film needs no servicing. It has no moving parts, no water and no boiler, and it is fully protected under the floor.
How does it compare with other systems?
Wet (water) underfloor heating needs pipework, a heat source and usually a screed, so it is more disruptive and expensive to install in an existing room, and it is slower to warm up. Carbon film is best for single rooms, extensions and renovations where floor height matters.
Electric cable mats are the right choice under tiles and stone, while carbon film is the better choice under floating floors.
Radiators and convector heaters warm the air, which rises to the ceiling. Underfloor heating warms the room from the floor up, giving even, draught-free comfort.
Frequently asked questions
How long does carbon heating film last?
Correctly installed, the film is expected to last for decades. Our carbon heating film comes with a 20-year guarantee.
Can it go under any type of floor?
No. It is designed for floating floors such as laminate, engineered wood and click flooring, and for carpet only with a board overlay. It must not be used under tiles or glued-down floors.
Can I install it myself?
You can lay the insulation, film and vapour barrier yourself, but the electrical connection must be made, tested and certified by a qualified electrician.
Can I use it in a bathroom?
No. For bathrooms we recommend a heating mat under tiles, or an infrared panel or towel rail.
Which film output should I choose?
130 W/m² is our standard film and suits most rooms. Send us your room sizes and we will design the layout and list everything you need, free of charge.