Heating Systems

A variety of technologies are available for heating your house. In addition to heat pumps, which are discussed separately, many homes use the following approaches:

Furnaces and Boilers

By far the most common way to heat a home.

Most U.S. homes are heated with either furnaces or boilers. Furnaces heat air and distribute the heated air through the house using ducts; boilers heat water, providing either hot water or steam for heating. Steam is distributed via pipes to steam radiators, and hot water can be distributed via baseboard radiators or radiant floor systems, or can heat air via a coil. Steam boilers operate at a higher temperature than hot water boilers, and are inherently less efficient, but high-efficiency versions of all types of furnaces and boilers are currently available.

Wood and Pellet-Fuel Heating

Provides a way to heat your home using biomass or waste sources.

Before the 20th century, 90% of Americans burned wood to heat their homes. As fossil fuel use rose, the percentage of Americans using wood for fuel dropped, falling as low as one percent by 1970. Then during the energy crises of the 1970s, interest in wood heating resurfaced as a renewable energy alternative.

Newer on the scene are pellet fuel appliances, which burn small pellets that look like rabbit feed and measure 3/8 to 1 inch in length. Pellets are made from compacted sawdust, wood chips, bark, agricultural crop waste, waste paper, and other organic materials. Some pellet fuel appliances can burn a wide variety of biomass fuels, including nutshells, corn kernels, small wood chips, barley, beet pulp, sunflowers, dried cherry pits, and soybeans.

Electric Resistance Heating

Among the most expensive ways to heat a home.

Electric resistance heating converts nearly 100% of the energy in the electricity to heat. However, most electricity is produced from oil, gas, or coal generators that convert only about 30% of the fuel's energy into electricity. Because of electricity generation and transmission losses, electric heat is often more expensive than heat produced in the home or business using combustion appliances, such as natural gas, propane, and oil furnaces.

If electricity is the only choice, heat pumps are preferable in most climates, as they easily cut electricity use by 50% when compared with electric resistance heating. The exception is in dry climates with either hot or mixed (hot and cold) temperatures (these climates are found in the non-coastal part of California; the southern tip of Nevada; the southwest corner of Utah; southern and western Arizona; southern and eastern New Mexico; the southeast corner of Colorado; and western Texas). For these dry climates, there are so few heating days that the high cost of heating is not economically significant.

Electric resistance heating may also make sense for a home addition if it is not practical to extend the existing heating system to supply heat to the new addition.

Active Solar Heating

Uses the sun to heat either air or liquid and can serve as a supplemental heat source.

There are two basic types of active solar heating systems based on the type of fluid—either liquid or air—that is heated in the solar energy collectors. (The collector is the device in which a fluid is heated by the sun.) Liquid-based systems heat water or an antifreeze solution in a "hydronic" collector, whereas air-based systems heat air in an "air collector."

Both of these systems collect and absorb solar radiation, then transfer the solar heat directly to the interior space or to a storage system, from which the heat is distributed. If the system cannot provide adequate space heating, an auxiliary or back-up system provides the additional heat. Liquid systems are more often used when storage is included, and are well suited for radiant heating systems, boilers with hot water radiators, and even absorption heat pumps and coolers. Both air and liquid systems can supplement forced air systems. To learn more about these two types of active solar heating, see the following sections: or ask your Plumber how it can be done

Radiant Heating

Can draw on a number of energy sources, including electricity, boilers, solar energy, and wood and pellet-fuel heating.

Radiant heating systems involve supplying heat directly to the floor or to panels in the wall or ceiling of a house. The systems depend largely on radiant heat transfer: the delivery of heat directly from the hot surface to the people and objects in the room via the radiation of heat, which is also called infrared radiation. Radiant heating is the effect you feel when you can feel the warmth of a hot stovetop element from across the room. When radiant heating is located in the floor, it is often called radiant floor heating or simply floor heating.

Radiant heating has a number of advantages: it is more efficient than baseboard heating and usually more efficient than forced-air heating because no energy is lost through ducts. The lack of moving air can also be advantageous to people with severe allergies. Hydronic (liquid-based) systems use little electricity, a benefit for homes off the power grid or in areas with high electricity prices. The hydronic systems can also be heated with a wide variety of energy sources, including standard gas- or oil-fired boilers, wood-fired boilers, solar water heaters, or some combination of these heat sources.

Despite their name, radiant floor heating systems also depend heavily on convection, the natural circulation of heat within a room, caused by heat rising from the floor. Radiant floor heating systems are significantly different than the radiant panels used in walls and ceilings. For this reason, the following sections discuss radiant floor heat and radiant panels separately.

Small Space Heaters

Less efficient than central heating systems, but can save energy when used appropriately.

While forced-air heating systems rely on the same type of ducts used by heat pumps and air conditioners, water and steam heat systems use radiators that only deliver heat. To learn about maintenance and retrofit options for these systems, see:

Heat Distribution Systems