Radiant floor heating of the kind used in homes works on the principle of thermal radiation. Heat is created either by electrical resistance in a heating element, or it is given off by tubes charged with hot water. If radiant floor heating is being installed in an existing home, the more practical option is to use a system that consists of electrical heating elements on a fiberglass mesh backing, which can be placed under flooring materials. It is generally a good idea to consult with an electrician before installing this type of radiant floor heating, to make sure that all wiring and connections comply with applicable codes.
Before the installation, the required tools should be gathered. A sturdy pair of scissors and a utility knife are crucial as is an ohmmeter, to measure electrical resistance. A glue gun or staple gun should be used to hold the system in place on the subfloor. A marker and tape measure, as well as a notched trowel and thinset cement complete the list of needed tools.
Since the system is electrical, and may cover a large area, it is recommended to set apart a dedicated circuit for radiant floor heating. Once the electrical connections have been prepared, the system is positioned on the floor as desired by the homeowner. This is a good time to indicate the system’s final position with a permanent marker, as well as marking where there will be turns or cuts made to accommodate fixtures and cabinetry. When trimming the mesh-backed heating element, only the mesh should be cut, and never the heating element.
Before the heating system is attached to the subfloor, the resistance in the conducting wires is tested with an ohmmeter to verify that there are no shorts or breaks in the circuit which will affect the performance of the system. Once it has been tested, the system is attached to the subfloor with staples or glue. When the system is securely attached, a thin layer of latex modified thinset cement is applied over it. This layer should be about 1/8 inch (0.32 cm) thick.
After the cement has completely dried, another layer is applied, over which tile or other hard flooring is placed. Carpet is not recommended to be installed over radiant floor heating, because of its insulating effect which blocks heat transfer into the room. Before using the heating system, the thinset cement must be allowed to fully cure, which can take anywhere from two days to two weeks, depending on manufacturers specifications.