Radiant floor heating can be installed under wall-to-wall carpet if the carpeting isn't too thick or if the carpet is installed without a pad. A carpet and pad combination with an R-value of less than 2.5 is compatible and doesn't trap the generated heat beneath the carpet layers.
The R-value is a measurement of resistance to heat flow. The R-value carpet described above is thin enough to allow the radiant heat into the room. Anything thicker, such as a deep pile or a plush style carpet, may require an additional heating source to make the room comfortable. Area rugs don't pose much of a problem because the heat can enter the room through the uncovered floor space.
Heating mats are the preferred type of radiant heating for under carpet installation. The mats are cut to order and have tiny wires that heat up. For example, the heating mats offered by Step Residential are only 1.2 millimeters, or 3/64 of an inch, thick.
For installation, the carpet is pulled back, then the mats are installed and connected to a power source. The carpet is put back into place over the mats. Once the self-regulating mats reach optimum temperature, they use less electricity. This makes them both energy-efficient and safe for carpets because they don’t overheat.