By Popular Mechanics

A Hearst Magazine for AP Special Features

If you’re in tune with the latest news in home improvement, you’ve probably noticed that in-floor radiant heating has moved back onto the front page. What you may not know, though, is whether this type of heating makes sense for you – either as a retrofit in your present house, or in the home you hope to build one day.

The simple truth is that in-floor radiant heat has much to recommend it. It’s every bit as comfortable as the enthusiasts claim because it delivers heat in a way that the human body is almost uniquely built to appreciate.

Still, in-floor radiant heat is not for everyone. It can be too costly, too limited or just too difficult to install. And, just as important to many, it can’t incorporate air conditioning as a forced-air heating system can.

In-floor radiant heating is a hydronic system – that is, it uses hot water to warm your home. Unlike baseboard systems, though, radiant heating utilizes tubing under the floor to carry and disperse the heat. While there are several installation variations, the preferred method is to embed the tubing in a concrete slab.

The popularity of radiant heating is due to the special kind of comfort it offers. Conventional baseboard heating, whether electric or hydronic, first heats the air in the room, which then circulates through convection currents. The body’s direct contact with the heated air provides warmth.

However, a radiant heating system doesn’t heat the air. Instead the heat moves directly to the objects in the room. The difference is somewhat akin to warming your hands by a fire rather than using a hair dryer.

In-floor radiant heat also offers some practical advantages. Because the heat originates at your feet, and the comfort of our lower extremities has a lot to do with overall comfort, temperatures can be set lower, typically 65 F to 68 F instead of 70 F to 72 F.

Radiant systems also produce less air stratification than baseboard or forced air systems – the heat doesn’t end up on the ceiling, well above the comfort zone. In a radiant system, the temperature difference between floor and ceiling is usually a meager 2 F to 3 F. Moreover, heat loss through walls and windows, precisely where baseboard units and forced-air diffusers are located, is minimized because the air in the room is carrying less heat.

Unlike forced-air systems, radiant heating doesn’t increase air pressure in isolated rooms, which also means less heat loss through doors and windows.Radiant heat does not greatly affect the moisture content of the air and reduces the dust circulation associated with forced air. Then too, the absence of forced-air diffusers or baseboard heaters means greater flexibility in decorating.

Add to these benefits a heat-retaining thermal mass such as structural concrete or lightweight, thin-slab concrete, improved boilers, circulators and controls, and the energy savings over conventional systems can approach 30 percent.