Electric Radiant Floor Heating Systems
Radiant heating systems involve supplying heat directly to the floor or to panels in the wall or ceiling of a house. The systems depend largely on radiant heat transfer: the delivery of heat directly from the hot surface to the people and objects in the room via radiation (also called infrared radiation.)Electric radiant floor heating systems can be subdivided by the type of installation: those that make use of the large thermal mass of a concrete slab floor or lightweight concrete over a wooden subfloor (called 'wet installations); and those in which the installer "sandwiches" the radiant floor tubing between two layers of plywood or attaches the tubing under the finished floor or subfloor (called 'dry installations').
Electric radiant floors typically consist of electric cables built into the floor. Systems that feature mats of electrically conductive plastic are also available, and are mounted onto the subfloor below a floor covering such as tile.
Because of the relatively high cost of electricity, electric radiant floors are usually only cost-effective if they include a significant thermal mass, such as a thick concrete floor, and your electric utility company offers time-of-use rates. Time-of-use rates allow you to 'charge' the concrete floor with heat during off-peak hours. If the floor's thermal mass is large enough, the heat stored in it will keep the house comfortable for eight to ten hours, without any further electrical input (particularly when daytime temperatures are significantly warmer than nighttime temperatures). This saves a considerable number of energy dollars compared to heating at peak electric rates during the day.
Electric radiant floors may also make sense for additions onto homes for which it would be impractical to extend the heating system into the addition.
 Electric Radiant Floor Heat Mat 6 sq ft 2' x 3' 120V  US $57.00
|
 10 sq.ft 120 Volt Electric floor radiant heating system US $69.00
|
 Radiant Electric Floor Heating Mat - 10 sq"ft US $99.00
|
 Floor Heating Electric Radiant mat 120/240 VAC 10sq ft US $99.99
|
 Electric Tile Radiant Warm Floor Heat Heated Kit, 120V US $129.00
|
 Electric tile radiant floor heat heating mat system US $129.00
|
Types of Floor Installations
Wet installations embed the cables within a solid floor and are the oldest form of modern radiant floor systems. The cable can be embedded in a thick concrete foundation slab (commonly used in 'slab' ranch houses that don't have basements) or in a thin layer of concrete, gypsum, or other material installed on top of a subfloor. If concrete is used and the new floor is not on solid earth, additional floor support may be necessary because of the added weight. Consult a professional engineer to determine the floor's carrying capacity.
Due to recent innovations in floor technology, so-called "dry" floors, in which the cables run in an air space beneath the floor, have been gaining in popularity, mainly because a dry floor is faster and less expensive to build. But because dry floors involve heating an air space, the radiant heating system needs to operate at a higher temperature.
Some dry installations involve suspending the cables underneath the subfloor between the joists. Reflective insulation must also be installed under the cables to direct the heat upward. Cables may also be installed from above the floor, between two layers of subfloor.
At least one company has improved on this idea by making a plywood subfloor material manufactured with grooves and aluminum heat diffuser plates built into them. The manufacturer claims that this product makes a radiant floor system (for new construction) considerably less expensive to install and faster to react to room temperature changes. Such products also allow for the use of half as much cabling since the heat transfer of the floor is greatly improved over more traditional dry or wet floors.
Floor Coverings
Ceramic tile is the most common and effective floor covering for radiant floor heating, as it conducts heat well from the floor and adds thermal storage because of its high heat capacity. Common floor coverings like vinyl and linoleum sheet goods, carpeting, or wood can also be used, but any covering that helps to insulate the floor from the room will decrease the efficiency of the system. Wood flooring should be laminated wood flooring instead of solid wood. This reduces the possibility of the wood shrinking and cracking from the drying effects of the heat.