Hydronic 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.)
Hydronic (liquid) 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').
Hydronic 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 through tubing laid in a pattern underneath the floor. In some 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, remoteness of the site, and the cost of labor.
 1953 Radiant Floor Heating PG's American Brass print ad  US $10.00
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 2 Circuit Valveless Radiant Floor Heat Manifold US $14.95
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 Radiant Floor Manifold Flow Meter & Temperature Gauge US $15.99
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 VINTAGE RADIANT POLISH FLOOR MOP IN BOX (GREAT) US $17.99
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 RADIANT FLOOR HEAT MANIFOLD 2 CIRCUIT WITH VALVES US $22.95
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 Pex Tubing Clip Gun RB-5 Plumbing Talon Hydronic Radiant Floor US $32.00
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Types of Floor Installations
Wet installations embed the tubing within a solid floor and are the oldest form of modern radiant floor systems. The tubing 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 tubing 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 tubing underneath the subfloor between the joists. Reflective insulation must also be installed under the tubing to direct the heat upward. tubing 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 tubing 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.
If you want carpeting, use a thin carpet with dense padding and install as little carpeting as possible. If some rooms, but not all, will have a floor covering, then those rooms should have a separate tubing loop to make the system heat these spaces more efficiently. This is because the water flowing under the covered floor will need to be hotter to compensate for the floor covering.
