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Radiant heating has been around for at least 2,000 years, since wealthy Romans warmed their homes with open fires under tile and concrete floors. That long-ago innovation was simple but revolutionary because it eliminated interior fireplace smoke, which was channeled through chambers under the floors and into chimneys behind the walls. It was also a far more comfortable way to keep warm; instead of huddling around a fireplace in the main room, homeowners and guests could walk on a toasty floor anywhere in the house.

Today’s radiant heating systems have come a long way from Roman times, though they’re still “hidden” behind walls and floors. Now homeowners can heat their homes with electrically charged panels or by pumping heated water through a system of flexible rubber tubes. Radiant heat can be installed in walls or ceilings, although radiant-floor heating is the most popular form. Builders embed panels or tubing in concrete slabs or staple them to wooden subfloors in the same amount of time it takes to nail down a piece of plywood.

These innovations have made radiant heating systems a popular alternative to forced-air systems. According to the Radiant Panel Association (RPA), a trade group supporting radiant heating manufacturers and installers, the technology has been installed in nearly 60,000 homes annually for the past ten or twelve years.

How it works

To understand radiant heating, imagine standing next to a large window on a cold day. You feel chilly there because the window surface is colder than you are, not because the temperature in the room is lower near the window. “Radiant heat is heat transfer from a warm surface to a cold surface,” says RPA executive director Lawrence Drake. “When you stand next to a large, cold surface—whether it’s a window, a wall, or a floor—that surface is drawing heat right out of your body.” A radiant heating system creates more of a balance between you and cold surfaces in your home. By heating them, you decrease heat loss from your body, which makes you feel warmer.

Another helpful distinction is the difference between radiant heat, which is all around you, and warm air, which blows across your body. As long as warm air is blowing, you feel warm, but when it stops, your body begins to lose heat to colder surfaces around you. Radiant heat is more like constant sun. “Imagine standing in the shade of a tree on a cold day and then standing in the sunlight,” says David Johnston, president of What’s Working, an international consulting firm on green building and design (whatsworking.com). “The temperature outside is the same, but your body feels warmer under the sun.”