Replacing a Furnace
Although older forced-air and hot water
boiler systems had efficiencies in the range of 56% to 70%,
modern heating systems can achieve efficiencies as high as
97%, converting nearly all the fuel to useful heat for the
Conservation efforts and a new high-efficiency heating system
can often cut your fuel bills and your furnace's pollution
output in half. Upgrading your furnace or boiler from 56%
to 90% efficiency in an average cold-climate house will save
1.5 tons of carbon dioxide emissions each year if you heat
with gas, or 2.5 tons if you heat with oil.
Replacing Your Furnace Can be the Best Solution
If your furnace or boiler is old, worn out, inefficient,
or significantly oversized, the simplest solution is to replace
it with a modern high-efficiency model. Old coal burners that
were switched over to oil or gas are prime candidates for
replacement, as well as gas furnaces with pilot lights rather
than electronic ignitions.
Before buying your new furnace or boiler, first make every
effort to improve the energy efficiency of your home, then
have a heating contractor run a heat-loss calculation to size
your new furnace. Energy-efficiency improvements will save
money on the furnace, because your home will need a smaller
furnace. A properly sized furnace will also operate most efficiently.
If you live in a cold climate, it usually makes sense to
invest in the highest-efficiency system available. In milder
climates with lower annual heating costs, the extra investment
required to go from 80% to 90%-95% efficiency may be hard
to justify. When shopping for high-efficiency furnaces and
boilers, look for dependability, and look for the ENERGY STAR®
label. Buy a system with a good warranty and a reputable company
to back it up.
When buying gas and oil systems, specify sealed combustion.
Sealed-combustion furnaces bring outside air directly into
the burner and exhaust flue gases (combustion products) directly
to the outside, without the need for a draft hood or damper.
They generally burn more efficiently and pose no risk of introducing
dangerous combustion gases into your house. In furnaces that
are not sealed-combustion units, back-drafting of combustion
gases can be a big problem.