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.
Wood and Pellet-Fuel Heating
Provides a way to heat your home using biomass or
waste sources.
Electric Resistance Heating Among the most expensive ways to heat a home.
Active Solar Heating
Uses the sun to heat either air or liquid and can
serve as a supplemental heat source.
Radiant Heating
Can draw on a number of energy sources, including
electricity, boilers, solar energy, and wood and
pellet-fuel heating.
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
Heat is distributed through your home through a
variety of ways. Forced-air systems use ducts, and
since these are also used for central air
conditioning and for heat pump systems, they are
discussed separately in the Supporting Equipment
section. Likewise, unique heat distribution systems
are employed for radiant heating and are discussed
in that section. That leaves two systems that apply
broadly to heating systems: steam radiators and hot
water radiators.
Steam Radiators
Steam heating is one of the oldest heating
technologies, but the process of boiling and
condensing water is inherently less efficient than
more modern systems, plus it typically suffers from
significant lag times between the boiler turning on
and the heat arriving in the radiators. As a result,
steam systems make it difficult to implement control
strategies such as a night setback system.
The first central heating systems for buildings used
steam distribution because steam moves itself
through piping without the use of pumps.
Non-insulated steam pipes often deliver unwanted
heat in unfinished areas. Therefore, pipe insulation
in these areas is usually very cost effective. Care
should be used to install fiberglass pipe insulation
that can withstand the high temperatures of these
delivery pipes.
Regular maintenance for steam radiators depends on
whether the radiator is a one-pipe system (the pipe
that supplies steam also returns condensate) or a
two-pipe system (a separate pipe returns
condensate). One-pipe systems use automatic air
vents on each radiator, which bleed air as steam
fills the system and then shut automatically when
steam reaches the vent. A clogged air vent will keep
a steam radiator from heating up. Air vents can
sometimes be cleaned by boiling them in a water and
vinegar solution, but usually need to be replaced.
Steam radiators can also warp the floor they are
sitting on and their thermal expansion and
contraction over time can dig ruts into the floor.
Both of these effects can cause the radiator to
tilt, preventing water from properly draining from
the radiator when it cools. This will cause banging
noises when the radiator is heating up. Shims should
be inserted under radiators to pitch them slightly
toward the pipe in a one-pipe system or toward the
steam trap in a two-pipe system.
In two-pipe systems, older steam traps often stick
in either the open or closed position, throwing off
the balance in the system. If you seem to have
problems with some radiators providing too much heat
and others providing too little, this might be the
cause. The best approach is often to simply replace
all the steam traps in the system.
Steam radiators located on exterior walls can cause
heat loss by radiating heat through the wall to the
outdoors. To prevent such heat loss, you can install
heat reflectors behind these radiators. You can make
your own reflector from foil-covered cardboard,
available from many building supply stores, or by
mounting foil onto a foam board or other similar
insulating surface. The foil should face away from
the wall, and the reflector should be the same size
or slightly larger than the radiator. Periodically
clean the reflectors to maintain maximum heat
reflection.
Hot Water Radiators
Hot-water radiators are one of the most common heat
distribution systems in newer homes, second only to
forced-air systems. They may be a baseboard-type
radiator or may be of an upright design that
resembles steam radiators. The most common problem
in hot-water systems is unwanted air in the system.
At the start of each heating season, while the
system is running, go from radiator to radiator and
open each bleed valve slightly, then close it when
water starts to escape through the valve. For
multi-level homes, start at the top floor and work
your way down.
One way to save energy in hot-water systems is to
retrofit them to provide separate zone control for
different areas of large homes. Zone control is most
effective when large areas of the home are not used
often or are used on a different schedule than other
parts of the home. A heating professional can
install automatic valves on the hot-water radiators,
controlled by thermostats in each zone of the house.
Using programmable thermostats will allow you to
automatically heat and cool off portions of your
home to match your usage patterns.
Zone control works best in homes designed to operate
in different heating zones, with each zone insulated
from the others. In homes not designed for zone
control, leaving one section at a lower temperature
could cause comfort problems in adjacent rooms
because they will lose heat to the cooler parts of
the home. Zone control will also work best when the
cooler sections of the home can be isolated from the
others by closing doors. In some cases, new doors
may be needed to isolate one area from another.
Cooler parts of the home should be kept around 50°F
to prevent water pipes from freezing; never shut off
heat entirely in an unused part of your home.
