Radiant heating is rapidly becoming a popular option in new home construction in the United States due to its cost-effective efficiency, but the concept dates all the way back to ancient Rome, where slaves tended fires that sent hot air through channels under elevated floors adorned by elegant marble. There are three different radiant heating systems: hydronic, electric, and air-heated. Electric and hydronic radiant heating systems are more efficient, and consequently more popular, than air-heated systems. Heat from a radiant system does not rise like heated air from a traditional heating unit; it spreads in all directions. This characteristic makes it possible to heat a large area using a lower temperature.
Electric radiant heating systems are the most versatile when it comes to installation. Rolled cables are attached in a looping pattern via braces to mats, mesh, or film constructed of resilient, heat-conductive materials. The mats can be embedded in the concrete slab during construction, installed under the subfloor, or even placed directly under the flooring, depending on type. Due to the versatility of installation options, electric systems are frequently the best choice for after-construction additions.
Electric floor heating is controlled by independent zone thermostats that can be set to heat just the floor for barefoot comfort on chilly days, to raise the temperature of a single room, or to heat an entire house. No moving parts means no maintenance. This convenient method of heating is also gaining popularity as a method to de-ice driveways and sidewalks as an environmentally friendly alternative to chemicals or salt and a people-friendly alternative to backbreaking shoveling.
Hydronic radiant heating systems circulate heated water through tubing embedded in the concrete slab. Due to the nature of the installation, it is usually done during construction. The advantage to a hydronic system is choice of power supply. The water can be heated with electric, solar, geothermal, natural gas, oil, wood-fired boilers, or any combination of these. Although most commonly hydronic systems are used for whole-house heating, they can be installed with zone control using a series of pumps.
Problems with this type of heating in the past were due to inferior tubing, sometimes requiring that the floor be ripped up for repair. Today’s materials are stronger, more leak-resistant, and should not become brittle with age, so the system is far less likely to require attention.
Hot air heating is simply not very efficient in comparison with electric and hydronic. For this system, air is heated and pumped through a system of pipes embedded in the floor. Because air cannot retain a great deal of heat, this method warms the floor itself, but cannot be counted on to warm an entire house, requiring that a secondary method of heating must be employed.
Flooring options compatible with radiant heating
Before you consider types of flooring for your radiant heating system, check with a professional. If you’re installing radiant heat in a new home, flooring choice should be carefully considered, and measures should be taken by the builder to insure dry installation. After a hydronic heating system is installed, most experts agree that the heat should be turned on and run for at least 3-6 days before the flooring is installed to leach any moisture from the concrete. If the slab itself is less than 60 days old, extend the drying time to 30-60 days, especially if you are using any kind of wood or laminate flooring. Always consult the flooring manufacturer’s instructions for exact drying time instructions.
Porcelain, ceramic, and stone tile
Tile and stone are ideal types of flooring to use with a radiant floor heating system. All are excellent heat conductors, do not expand and contract with heat and are highly resistant to warping or cracking, making porcelain, ceramic, or stone tiles your best choice for floor covering over radiant heating.
Carpet is not a bad choice of floor covering for a radiant heat system, but is not a good conductor for heat. As a result, your toes may be toasty but it will be more difficult to heat the entire room. The best carpeting option for radiant heat is a thin carpet with a low pile, Berber for example, and a thick pad.
Laminates can be used with caution. Careful consideration must be given to the installation to insure the underlying floor structure and concrete is dry in order to minimize changes dues to heat and moisture and avoid warps and cracks. Adhesives are also important to consider. Follow manufacturer recommendations for best results.
Vinyl has come a long way since the old linoleum floors of the sixties. While it is not an ideal choice for heat conduction, some vinyl flooring can be installed over radiant heat with a temperature limit set by the manufacturer. Poor quality vinyl flooring may discolor or emit a foul odor when heated.
Hardwood and Bamboo
Wood has a natural tendency to react to both temperature and moisture, so installation over radiant heating has to be very carefully engineered and will be far more successful in a dry climate.
Wood is not a static material. It swells and contracts with changes in temperature and moisture in the air, which can be problematic when it comes to floors, especially in areas of high humidity. For best result, look for a kiln-dried wood that is quarter-sawn as opposed to plane-sawn. Quarter-sawn wood has a tendency to expand in thickness and not width, so it’s less likely to warp or crack. Many experts recommend that you run the radiant heating for at least 72 hours before taking delivery of the wood flooring, then store the wood in the room where it will be installed with the radiant heating turned on to help the wood acclimatize to the moisture content in the air. The drier the concrete, the more successful the installation will be. Installing hardwood over a radiant floor heating system is tricky, but can have warm and beautiful results. Always raise the heat gradually, allowing the wood to adjust. Sudden temperature changes can cause damage to the structure of the floor.
One wood flooring option generally more suited to use with radiant heat is engineered hardwood flooring. Engineered hardwood flooring is made up of several layers of solid wood or fiberboard, much like plywood or particle board. The multiple layer construction makes engineered flooring much more dimensionally stable and less likely to expand or contract with changes in temperature. In addition, most engineered flooring can be “floated” making it ideal for installation over concrete. The suitability of an engineered hardwood floor will depend on its construction, and the wood species and adhesives used to in its manufacture.
Always consult the manufacturer or retailer to determine whether a particular type of wood flooring is suitable for installation over radiant heat and whether use with radiant heat will affect the product warranty.