Heated Floor (Radiant Heat): A Homeowner's Guide

Radiant floor heating warms a room by heating the floor surface and allowing heat to radiate upward into the space. In residential remodeling, electric radiant floor heating is the most commonly installed type, using a network of resistance heating cables or a mat embedded beneath floor tile.

In Phoenix, radiant floor heating is a popular upgrade in primary bathroom and kitchen remodels. Cool tile floors in air-conditioned Phoenix homes, particularly on winter mornings when temperatures drop into the 40s, are a daily discomfort that a heated floor eliminates at modest cost.

At Phoenix Home Remodeling, electric radiant floor heating is specified during the design phase and installed during the rough-in and tile installation phases. The heating mat or cable is embedded in the tile setting mortar beneath the finished floor tile.

Because the floor is already being opened. Tile removal, subfloor preparation, and new tile installation are already in the scope of the remodel. Adding a radiant heating mat to a floor that is being tiled anyway adds modest material cost and minimal labor, because the floor work is already happening. Adding radiant heat to an existing bathroom without a remodel requires removing all the tile, installing the mat, and retiling the entire floor, which is a full bathroom floor project by itself.

• Heating cable or mat: Heating cables are flexible wires serpentined across the floor at specified spacing. Heating mats are cables pre-attached to fiberglass mesh at correct spacing. Mats are easier to install correctly in regular-shaped spaces. Cables offer more flexibility in irregular or complex shapes.
• Thermostat and sensor: A programmable thermostat controls heating schedule and temperature. A floor sensor embedded in the mortar monitors floor temperature and prevents overheating. Some thermostats include air temperature sensors for a combined control strategy.
• Electrical circuit: Most bathroom radiant floor systems require a dedicated 120-volt circuit. Larger floor areas may require 240-volt. The electrical panel must have capacity for the additional circuit.
• Mortar compatibility: The heating cable or mat is embedded in thin-set mortar beneath the tile. Mortar thickness must be adequate to fully encapsulate the cable and provide a smooth surface for tile. Some manufacturers specify particular mortar products.
• Testing: Quality manufacturers provide warranties of twenty-five years or more on the heating element. The cable must be tested with a resistance meter before and after tile installation to confirm it was not damaged during the tile setting process.

Electric radiant heating works under tile, stone, and concrete. It can work under some hardwood and laminate products but compatibility must be confirmed against the specific manufacturer's warranty requirements. Radiant heat is most effective under tile and stone because these materials conduct and radiate heat well. Carpet is not compatible with radiant floor heating.

For a typical bathroom, no. The heating element in a standard bathroom draws approximately 12 watts per square foot. A 60-square-foot bathroom floor draws approximately 720 watts when running. On a timer running two hours in the morning and one hour in the evening, the operating cost is very modest. The thermostat's floor sensor also ensures the system runs only as long as needed to reach and maintain the set temperature.

We install the heating mat or cable during the tile preparation phase, after floor substrate is prepared and before tile is set. The thermostat location is specified during the design phase and electrical rough-in is run during standard rough-in. We test the heating element before and after tile installation. The thermostat is programmed at project completion and homeowners are walked through operating the system.

• What is the cost to add radiant floor heating to my bathroom tile scope?
• Does my electrical panel have capacity for the additional circuit?
• What thermostat are you specifying and where will it be located?
• How will the cable be tested before and after tile installation?
• What is the manufacturer warranty on the heating element?

See also: Bathroom Remodel Budget, Backer Board (Tile Installation), Walk-In Shower Design, GFCI Outlet, Construction Sequencing, Steam Shower