Heating System Basics

The majority of American homes are heated with a forced-air furnace, most commonly fueled by natural gas, but also by electricity, liquid propane or fuel oil.

How a Furnace Works

A furnace works by drawing air inside a heat exchanger, where it is warmed with a flame of natural gas, propane or fuel oil, or with heated electric coils. A blower sends the warmed air through the house via metal ducts; it enters the room through a register or grill in the floor or wall. Indoor air is circulated continuously through the system, so a furnace filter is used to contain dust, pollen and other airborne particles.

An older home might have a boiler, fueled by natural gas, liquid propane or fuel oil. A boiler works by heating water and circulating is through pipes to radiators, where it warms the surrounding air. Unlike a furnace, a boiler doesn’t circulate air throughout the house, which is why the air in a boiler-heated home might seem “stuffier.”

Electric Heat Pumps

Another home heating option is an electric heat pump. This unit works by moving existing heat from one area to another in one of three ways:

• Air-to-air: An condenser absorbs heat from the outdoor air (even the coldest air contains some heat) and transfers it to an indoor heat exchanger inside the home. Indoor air is warmed in the heat exchanger and circulated throughout the home. During the summer, the process is reversed to cool and dehumidify the home.
• Water-to-air: Instead of extracting heat from outside air, this type of pump absorbs heat from ground water or surface water, such as a farm pond.
• Ground-to-air: Also known as a geothermal system, this type of heat pump uses underground loops to absorb heat from the earth. Geothermal systems are usually installed in newly-built homes, but can also be used in existing homes.

One advantage of a heat pump is that it provides both heating and cooling capabilities in one unit. Electric heat pumps are usually supplemented with a backup system, such as radiant floor heaters or baseboard units (see below), in case of extended periods of extreme temperatures. Heat pumps also use filters to reduce airborne particles and keep the unit clean.

Electric Resistance Heating

Electric resistance heating, usually found in the form of baseboard heaters, was popular during the 1940s and 1950s, and is often used in multi-family dwelling like apartment houses. A baseboard unit has an electric heating element encased in metal pipe. Air warmed by the heating unit rises to the top of the room, and cooler air is drawn into the bottom of the heater. Each unit has a separate thermostat to allow for different temperatures in each room.

Radiant Heating

Radiant heating is making a comeback in many new homes. Instead of circulating heat by moving the air in the room, a radiant system heats objects – including people. The most common form is radiant floor heating, which uses electric cables or small tubes of hot water embedded in a concrete floor or under a tiled floor. During the height of its popularity during the ’40s and 50s, radiant heating was also installed in wall or ceiling panels.

Homeowners in the Midwest usually use radiant heating as a supplement to a primary heating system. It’s most often installed under the floor in uncarpeted areas such as kitchens, bathrooms, laundry rooms and garages. For added luxury, radiant heating cables can be embedded in a driveway – no more shoveling!