Buying Radiant Heat
A radiant floor heating system is a method of heating a room or a house by heating the floor. Unlike conventional warm-air furnaces, boilers and heat pumps, which heat the air in a house, radiant heat transfers 60% of its heat, which "radiates" directly through the floor. Only 40% of the heat transfer is to the air. The effect is that people generally feel warm, even though the air temperature is cooler. This provides a more consistent sense of comfort than hot air that is blown from vents or heat rising from radiators.
Radiant heating has a long history -- there is evidence that it was used in Mongolia (China) more than 6,000 years ago. More recently, the Romans used a form of radiant heating called a hypocaust in houses and public baths. Floors were raised on short pillars, leaving space beneath for a furnace to circulate warm air.
The heating system can transfer heat to the floor in a couple of ways. Sub-floor electric mats or plastic tubes filled with hot water are both common.
Heating with Water
In a hydronic (hot water) system, the water itself is heated with a boiler. The boiler can be powered in many ways: with oil, propane, electric, or even solar heat. The hot water tubing is typically embedded in concrete, which acts as a thermal mass to store the heat. You can finish the floor in concrete, tile, stone, laminate, wood, or even carpet in some cases. Tile is often a preferred finish, as it conducts heat well and its mass can help to store additional heat.
Heating with Electricity
Electric systems typically work in one of two ways: either electric mats are mounted above or below the subfloor, or electrical cables are embedded in the floor itself. Buying electricity for these systems can be expensive, so this approach works best if you have a thick concrete floor to act as a thermal mass. This can be heated overnight when electricity is available at off-peak rates, and the concrete pad will slowly release its heat over 8 or more hours.
For more information on hydronic and electric radiant heating, visit www.Radiant-floor-heating.com.
Installing Radiant Heat in your Existing Home (Retrofitting)
There are essentially two ways to retrofit your existing house. One way is tearing up the existing floors and installing radiant heat. As you may guess this can be very expensive, but it may make sense if you only want to install radiant heat in a single room. The second method is to apply an electric mesh system to the joists underneath an existing floor. The heat then rises through the floor. This is often a very economical way to heat a floor when you can access the joists underneath (for example, through the basement).
Radiant floors can be installed upstairs and downstairs. Radiant floor heat can be used as your only heat source, or it can be used in conjunction with a warm air furnace, boiler or heat pump. For more detailed information see our article on installing radiant heat.
Other Advantages and Disadvantages of Radiant Heat
"Comfort" is a state of mind rather than a read-out on a thermostat, but most experts agree that people prefer the consistent warmth of radiant heat over heating the surrounding air through conventional means. Radiant heat can be more efficient (and cheaper to operate) assuming you design your system well. Other advantages include quiet operation, the fact that radiant systems don't distribute potentially dirty air around your house, and complete decorating freedom.
In terms of disadvantages, keep in mind that radiant heat systems can't be used for cooling. If you need to cool as well as heat your home, you may want to consider a warm air furnace or heat pump whose duct-work and air handler can perform double duty by also keeping your house cool.