Electric-resistance radiant floor heating works like a toaster. When electric current travels through electric wiring, it generates heat.

With this type of heating system, special floor-heating cables or woven mats, foils, or panels with built-in wires are installed on, in, or under the subfloor.

Then they're hooked up to an electrical circuit and a control such as a thermostat. When the control is turned on, electric current that moves through the cables or wires heats the floor.

With cable systems, a fairly large electric heating cable is wound back and forth on the subfloor. Concrete or gypsum cement is poured over it, resulting in a slab with the cables inside it. This becomes a base for finish flooring such as tile or stone.

This base is flat, solid, and full of thermal mass for retaining and slowly releasing heat. If your utility company offers lower rates during off-peak hours, you can save money by heating such a floor during off-peak hours; the floor will retain the heat and release it slowly during peak hours.

Because of the high cost of electricity in most regions, electric radiant floor heating is generally reserved for bathrooms, kitchens, or small room additions that are expensive or difficult to heat by extending the existing heating system. Radiant floor heating is at its absolute best in bathrooms with stone or tile floors that would otherwise be cold underfoot. Manufacturers suggest that a 120-square-foot room may cost only about 40 cents a day to heat.

Most mats, foils, and panels are fastened between floor joists, laid between joists on top of fiberglass insulation, or embedded in the subfloor. A relatively new foil product, the Environ II System made by WarmlyYours, has a UL rating that allows safe installation directly beneath a carpet or laminate floor on the underlayment pad.

In the relative world of radiant floor heating, this is very easy and inexpensive to install and, because it is placed so close to the floor's surface, very responsive and effective at heating.