How Does Radiant Floor Heat Work?
-
Radiant Systems Use Convection to Spread Heat
-
Unlike most traditional home heating systems, radiant floor heat does not rely on ducted forced air to spread heat through a room. Radiant heat transfer occurs when elements within the floor itself are heated, circulating rising heat from the floor surface around the rest of the room in a process called convection. The floor can be heated in several ways: via air, electricity, or water. Home radiant floor heat systems are typically of either electric or "hydronic" design. The first of these can be installed as a separate layer, but electric systems most often use electric cables set in concrete because of its thick, heat-conductive texture that can store and radiate heat for hours after the initial heating process. The hydronic or liquid systems utilize a boiler that heats water, which is then pumped through tubes in the floor or under the finished floor.
Types of Floor Installations
-
Electric or hydronic radiant floor heat systems can each be installed in more than one way. In "dry" installations, the heating elements occupy their own layer between a permanent subfloor and a finished layer above. Electric heating installed as a separate layer generally uses plastic mats containing the electric wires and placed on the subfloor. For "wet" installations, those in which the heating elements are set directly into the concrete, the electric elements can either be installed within two inches of the surface of the concrete slab as it is poured during construction, or added within a new layer of concrete or a layer of similarly-textured material such as gypsum. A concrete slab, normally uncomfortably cold in winter, becomes a fine heating device when heating elements are installed, since it is capable of storing heat for many hours. The stored heat rises through the floor covering into the air without the dust or allergens associated with forced-air heating systems. The best finished floor surface for radiant heat systems is generally ceramic tile because of its heat-conducting qualities that are similar to concrete. Wood floors or thick carpeting, which tend to act as insulators, can reduce the efficiency of the entire radiant floor heat system and necessitate turning up the heat. In addition, the heat can crack or otherwise damage fine wood flooring.
The Efficiencies of Radiant Floor Heat
-
Radiant floor heat is more efficient than electric baseboard heaters or forced-air heating, which tend to lose some heat as they operate. Hydronic (water-based) systems are especially efficient because their boilers (like radiator systems) require comparatively little electricity to operate. Additionally, the boilers can operate from solar power, wood, natural gas or oil instead of utility-generated electric current. "Wet" electric or hydronic installations that do use standard electric power are the most cost-effective, since they can be heated up during lower-rate periods such as the overnight hours and allowed to radiate passively during the day.
-
