Radiant heating systems involve supplying heat directly to the floor or to panels in the wall of a home. The systems depend largely on radiant heat transfer; the delivery of heat directly from a hot surface to the people and objects in the room via the radiation of heat, which is also called infrared radiation. Radiant heating occurs when you can feel the warmth of a hot stovetop element from across the room. When radiant heating is located in the floor, it is often called radiant floor heating or simply floor heating.
Radiant heating has a number of advantages. It is more efficient than baseboard heating and usually more efficient than forced-air heating because no energy is lost through ducts. The lack of moving air can also be advantageous to people with severe allergies.
Hydronic (liquid-based) systems use little electricity, which is a benefit for homes off the power grid or in areas with high electricity prices. The hydronic systems can be heated with a wide variety of energy sources, including solar thermal hot water panels, standard gas- or oil-fired boilers, wood-fired boilers, or some combination of these heat sources.
Despite their name, radiant floor heating systems also depend heavily on convection – the natural circulation of heat within a room – caused by heat rising from the floor. Radiant floor heating systems are significantly different than the radiant panels used in walls and ceilings.
Description of Radiant Heat floors
The type of installation that is required can further subdivide all three types: those that make use of the large thermal mass of a concrete slab floor or lightweight concrete over a wooden subfloor (these are 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 (“dry installations”).
Hydronic Radiant Floors
Hydronic (liquid) systems are the most popular and cost-effective radiant heating systems for heating-dominated climates. Hydronic radiant floor systems pump heated water from a boiler and /or solar system through tubing laid in a pattern underneath the floor. In most Eco Depot USA systems, the temperature in each room is controlled by regulating the flow of hot water through each tubing loop. This is done by a system of zoning valves or pumps and thermostats. The cost of installing a hydronic radiant floor varies by location and also depends on the size of the home, the type of installation, the floor covering, and remoteness of the site.
Air-Heated Radiant Floors
Because air cannot hold large amounts of heat, radiant air floors are not cost-effective in residential applications, and are seldom installed. Although they can be combined with solar air heating systems, those systems suffer from the obvious drawback of only being available in the daytime, when heating loads are generally lower. Because of the inefficiency of trying to heat a home with a conventional furnace by pumping air through the floors, the benefits of using solar heat during the day are outweighed by the disadvantages of using the conventional system at night. Although some early solar air heating systems used rocks as a heat-storage medium, this approach is not recommended.
Electric Radiant Floors
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 (approximately 9 p.m. to 6 a.m.). 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. (This saves a considerable number of energy dollars compared to heating at peak electric rates during the day.)