Radiant floors are heated either with electric resistance cables or hot water flowing inside tubing.
Electric systems are typically supplemental, not meant to be the sole heat source for a room. The cables, which are often pre-attached to mats for ease of installation, are installed over the subfloor in a bed of thin-set mortar. Ceramic or stone tile are popular finished floor choices. There are also radiant electric floor heating pads that can be installed under laminate and other floating floors, such as engineered hardwood. One manufacturer, Thermosoft International, makes pads that produce 31 BTUs per square foot. Installation is simple. Just roll it out, tape it in place, cover with floating-type flooring, and make the electrical connections. No mortar is required.
Don’t want to pull up your existing flooring? Companies such as SunTouch make electric radiant pads that fit in joist bays under the subfloor. You will, of course, need access to the bays from a basement or crawl space. Batts of fiberglass insulation are installed under the mats so most of the heat goes up, not down.
Hydronic systems are usually designed to heat an entire house. Water is heated to between 100 and 120 degrees Fahrenheit by a boiler and circulated through tubing under floors. The tubing can be installed in several ways: embedded in a concrete slab, over an existing slab in cement, stapled under subflooring, or fitted inside the channels of specially designed subfloor panels. Any kind of finished flooring, including hardwood strip flooring, vinyl, or carpeting, can be installed above it.
(Note: Some installers may recommend engineered wood rather than solid wood flooring products in homes with high moisture levels. Otherwise, changes in moisture content can cause wood planks to cup, bow, or warp.)