My Introduction to Radiant Floor Heat
Twenty years ago I visited another modular builder’s residence on a cold February day. It was a nicely appointed cape cod with a front-to-back family room on one side and a complimentary garage flanking the other side. When I entered the family room I was immediately struck by how comfortable I felt. At first I thought it was the number and style of windows that looked out onto a peaceful snow covered patio. Then I thought it was the decor, which was richly traditional. The builder’s wife, who was giving me a tour, smiled and said, “You look confused, and I bet I know why. Your feet are warm.” I undoubtedly looked even more confused until she explained that the tile floor had radiant floor heat.
Forced Air Heat vs. Radiant Floor Heat
Have you wondered why you sometimes (maybe always) feel cold even though the thermostat for your forced hot air heating system is set to 72 degrees? It’s not you! It’s because the warm air rises to the ceiling and falls back down as cool air. Your toes become cold why your head stays warm. This effect is amplified by the on and off cycling of the system, which warms you quickly but then chills your bones when the air stops pumping through the ducts.
With radiant floor heat, on the other hand, the heated floor transmits its warmth to the surrounding objects. You remain comfortably warm because the coldest air is at the ceiling rather than your feet, and the floor and everything it touches remains at a constant temperature. By warming you from your feet up, radiant floor heat keeps you feeling toasty at a lower temperature.
Radiant floor heating systems can heat an entire home or individual rooms. Bathrooms, kitchens, and mudrooms are popular candidates for this enhanced comfort. When installed in selected rooms, the temperature is controlled with individual thermostats. The remaining rooms are heated with a conventional system.
Two Types of Radiant Floor Heat
An example of how the tubes are laid out for hydronic radiant floor heat.
Materials for electrical radiant floor heat.
There are two basic types of radiant floor heat: hydronic and electric resistance. Hydronic systems pump heated fluid through small tubes under the finished flooring. The fluid is usually a mix of water and anti-freeze, such as propylene glycol The heat source is a boiler, water heater, or heat pump, with the heat transferred by the recirculation of the fluid between the floor and the heat source.
Electric resistance systems work with electric wires set underneath the floor. They function much like the wires in an electric blanket. Because they use fewer components and are easier to install, they are less expensive to set up than hydronic systems for single rooms. However, they are more costly to operate.
Installation of Radiant Floor Heat
Both types of radiant floor heating systems can be set in a concrete, mortar, or gypsum bed, placed under the floor covering, or attached directly to a wood sub floor. The tubing for radiant floor heat can be installed in specially made plywood with precut channels, which enables you to install carpeting and wood flooring directly over the plywood. Ceramic tile floors should be cast in a mortar bed or on a cement backer board, while vinyl flooring needs to be placed on an underlayment.
Finished Flooring over Radiant Floor Heat
You can use most any type of finished flooring over either type of radiant floor heating system, although some materials work better than others. Tile, stone, and concrete transfer and hold heat best. Solid wood floors will shrink and expand because of the heat, but the new “engineered wood” floors hold up better. If you install vinyl or laminated flooring, make sure they can withstand the heat. Keep in mind that carpets will reduce the heat flow, as they will act as insulation.
Advantages of Radiant Floor Heat
Radiant floor heat has a few notable advantages over conventional systems in addition to superior comfort. Many people like the fact that they’re hidden and silent. If you’ve ever lived with banging radiators or whistling registers, you’ll appreciate radiant floor heat. Anyone with allergies will value them because there is no dust- or allergen-blowing ductwork. And for those who want to increase the energy efficiency of their home, radiant floor heating systems are an efficient way to heat, increasing comfort as they reduce energy costs.
For more information about installing radiant floor heat, see Modular Home Specifications and Features and The General Contractor’s Responsibilities for Building a Modular Home in my book The Modular Home.