Installing Radiant Heating

Radiant floor heating has been around since the Romans channeled hot air under their floors. Modern systems use electric mats or hot water pipes. Underfloor mats may install more quickly, but above-floor mats are more efficient because the heating element is in direct contact with the finished flooring.

Hydronic systems carry hot water through PEX tubing, a plastic material that stays flexible and withstands heat. Putting in PEX tubing is an easy do-it-yourself project, but hooking up the pipes and installing a boiler calls for a licensed plumber.

Conventional heating systems create different temperature zones in different parts of a room. These temperature zones can make different sections or levels of the room uncomfortable and prompt you to raise the heat setting to warm up the cool spots. Radiant floor heating warms the entire area to a more consistent, comfortable temperature. It also heats without blower noise and doesn't raise dust.

Before you purchase a radiant heating system, sketch the room where it will be installed. Mats or piping are not required under closets, major appliances, and vanities. In bathrooms, about 50 percent of the floor area should be heated; in kitchens and living areas, about 60 percent.

Not all systems are wired the same. Some use flat ribbon strapping and cable leads that connect to the thermostat. Others must be wired to a switch. The illustration shows a typical wiring for a thermostat controlled system. Follow the manufacturer's instructions exactly.

Carefully sketch the system wiring on a dimensional plan. Note the location of the thermostat and any other electrical switches or outlets in the room. Measure the location of the switch/thermostat from a reference point, such as an adjoining wall, and transfer this measurement to the subfloor in the room below.

If possible, locate the thermostat on an interior wall; this will make drilling through the floor plate easier. Place the thermostat as close to the power source as possible. Long lead wires from the power source can reduce the efficiency of the system.

You can install almost any finished flooring over radiant heat, but the key to the system's performance is how well the flooring material conducts heat.

Ceramic tile and stone are the best conductors and will allow the system to run more efficiently than other materials. Parquet and laminate are also good conductors. Carpet tile is thinner than broadloom carpet but still acts as insulation and won't distribute heat as well as solid materials. Vinyl tile has almost no R-value at all, so it's a good choice but should not be heated above 85 degrees F.

No matter which system you install, put separate thermostats in each room to customize the heat for maximum comfort and efficiency.