Electric Radiant Floor Warming: The Affordable Luxury
Mountain climbers have an old saying: “Don’t cheat your feet.” A homeowner might consider this advice when building or remodeling a bathroom or kitchen floor.
For floors, homeowners know that ceramic, slate or marble tiles are attractive and durable alternatives to wood, carpet or vinyl. They want the beauty of tile floors, but their feet tell them they’re cold.
While most people are comfortable with air temperatures of 65 to 75 degrees, they tend to feel uncomfortable if there’s more than a 5-degree difference between the surface temperature (80 to 85 degrees) of the head and that of the feet. A bare foot gives an immediate indication as to the comfort level of any floor. For this reason alone, tile is often not the flooring of choice.
With a tiny amount of heat supplied by a human foot, carpet fibers warm almost instantaneously to “foot” temperature, about 83 degrees. A ceramic tile can’t compete in this race: its mass needs a lot more heat for a longer amount of time. It would take approximately 30 minutes for a human foot to increase a 68-degree marble floor to foot temperature!
Radiant floor warming systems solve this problem — fast!
The most common radiant floor warming systems are either hydronic (circulating hot water in tubes in the floor) or electric (heating cables in the floor). Hydronic systems are more complicated, requiring pumps and valves and modulators and so on, and, as a result, are a lot more expensive to install than electric. Still, for whole house heating solutions, hydronics are a good choice. By contrast, electric systems are inexpensive enough for single room applications and simple enough for do-it-yourselfers.
Suitable for new construction or remodeling applications, electric floor warming systems include a network of cables installed in the mortar just below the tiles. These cables gently warm the tiles, operating on ordinary house current. While using a professional electrician is advised for those not comfortable working on electrical installations, these systems are generally easy to install and will not compromise the integrity of the tile installation.
Designing a floor warming installation first requires a determination of the area to be warmed. Calculating the total square footage will require collecting information from the blueprints of the room or actually measuring the area itself. It should be noted that areas that are inaccessible or under vanities, cabinets, or plumbing fixtures should not be included — there’s no need to heat floor area that won’t be walked on! When making the calculations it is advisable to design a layout that considers actual use and traffic patterns in the area to be warmed. Using care in measuring and calculating the area will help ensure that the proper cable is selected for the installation. Preformed mats can also be selected to simplify the installation, but these are usually only suitable for rectangular areas; odd shaped areas, such as “T’s” or “L’s” will often have cold spots if heated by mats.
Easy Heat’s Warm Tiles cables are available as an off-the-shelf product in a growing number of distribution channels, including retail. Easy Heat also provides mats in stock and custom sizes. Thermostats are also available with setback features to ensure that the cables are only heating the floor when the floor is being used. Floor heating thermostats differ from room heating thermostats in that they have a sensor that extends down into the floor to sense the actual floor temperature, and to control the cables accordingly, usually at about 85 degrees. Today, floor warming thermostats are available with sophisticated programming features as well.
A complete system often can be installed using an electric drill and other ordinary hand tools. The installation process can be completed in three phases that will likely correspond with the construction or remodeling phases of your home or building.
Phase one — Electrical Rough-in
During the electrical rough-in, the electrical box for the thermostat is installed, and the power supply cable pulled into it. Conduit holes are drilled into the wall plate (a two-by-four on the floor at the bottom of the wall) to enable the heating cable leads and thermostat sensor to be pulled into the electrical box.
Phase two — Install Cables
For new construction, the cables are installed only after the drywall is finished and immediately prior to the tile installation. The cables are provided with plastic strapping that is stapled to the floor, and the heating cable is simply woven over the floor on the strapping. The leads of the cable and the thermostat sensor are routed through the conduit holes and up to the electrical box. A “scratch coat” of mortar (just enough to cover the cables) is then applied and allowed to dry, usually just a day. Then, the flooring can be completed in the usual manner.
Phase three — Thermostat and Power Connection
The last phase calls for the installation of the thermostat and connection to the power source.
For more information on electric radiant floor warming call (877) EASYHEAT, or go to www.warmtiles.com. Warm Tiles is a registered trademark of Easy Heat Inc.
EDITOR’S NOTE: Using a thermostat, a typical floor warming system can be inexpensive to operate. A homeowner may visit the U.S. Department of Energy’s own Energy Information Administration’s web page at www.eia.doe.gov/cneaf/electricity/epm/epmt55p1.html to determine typical electrical usage. Using Easy Heat’s Warm Tiles square foot operating cost, for 40 square feet, one finds: 8.08 cents USA 2002 estimated residential national average kilowatt-hour rate (as of Aug. 28, 2002 per the EIA Web site above) X 8 hours typical daily operating time, using Easy Heat’s FTTK thermostat X 0.012 kilowatts used per square foot serviced by Easy Heat’s Warm Tiles FT1039 (120 Volts AC) = 0.77568 cents or less than 1 cent per square foot per day, or about $10 per month of operation.