When you feel the heat from an electric stove burner or sit in the sun on a winter day, you're feeling radiant heat. Radiant heat or infrared radiation warms objects directly, while conventional central heat circulates heated air.

People have been heating with radiant heat for centuries. Wealthy Roman homes, for example, were heated by a hypocaust, a fire-warmed space below the floor. The warmed floor then radiated heat. Radiators, which radiate heat from steam circulating through pipes, were once common in the United States, and modern versions are still popular in European homes.

Radiant floor heat is becoming a more popular option in new homes. Its advantages include warm floors and clean, quiet operation. The two major types are hydronic systems, in which a heated liquid, usually water, circulates in pipes laid in a pattern underneath the floor, and electric radiant floors. The liquid for hydronic systems can be heated with a variety of energy sources, including gas- and wood-fired or electric boilers and solar water heating. Hydronic floor heating can be quite efficient, but it has a fairly high initial cost, and the overall cost is less favorable in areas in which homes need a duct system for air conditioning.

Electric radiant floors, in which electric cables are built into the floor, work on the same basic concept as an electric blanket. The cables' resistance to the flow of electricity causes it to heat up. Electric radiant floor heat is cheaper to install than hydronic, but is more expensive to operate. Electric radiant floors are offered as a luxury feature in bathrooms because of the added comfort of stepping out of the shower onto a warm floor.

Electric baseboard heaters and wall- and ceiling-mounted radiant panels are fairly inexpensive and easy to install, but more expensive than heat pumps, because they are electric resistance devices. But they can be more efficient, allowing you to tailor the heat in one area to suit your requirements – such as warming the room occupants rather than the air, while keeping the rest of the space cooler. Because of their initial low cost, these heaters are often used in vacation homes and rental properties. They are also used in building additions where it would be difficult to extend the existing heating system.

The Case for Radiant Heat

We looked into using radiant ceiling panels to heat an infrequently used meeting room in a portion of a large building. Not only would it have taken hours to warm the entire building, but also a good deal of energy. Radiant panels heated the meeting space like turning on the lights. In the case of a cold and drafty office space, we also used an under-desk foot warming radiant pad. The office was next to the outside door and people frequently held open the door. A conventional space heater was ineffective. The radiant panel used much less energy, produced more even heat and better comfort.