Types of Heating Systems
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
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 home.
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 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
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!
Tips for how
to improve efficiency