Energy Loss
Improperly sealed fireplaces are noted as being one of the worst heat loss
areas in the home, costing you money in home heating bills. A closed fireplace
damper is often the largest and most neglected hole in the exterior envelope of
a house. Dampers are intended to close off the chimney, but are often left open.
When dampers are closed they do not provide a good seal and are quite ineffective due to heat warping.
In a 1990 study, designed to measure the leakage area of fireplace with
and without the damper closed, Energy Options Northwest had this impressive
finding; the effective leakage area (ELA) of the fireplace dampers averaged
about 30 square inches when closed. As a frame of reference, the total ELA of
typical houses built to moderately tight standards is between 70 and 120 square
inches. This is like leaving a door open for all of you costly home
heating/cooling to escape through.
Open fireplaces also allow annoying and uncomfortable downdrafts.
Back drafting brings cold air in winter that must be heated, and warm air in
summer that must be cooled.
A complaint we often hear is that windows and doors seem to have a cold
breeze coming through them. This is caused by a condition known as the stack
effect
. Between the higher and lower
pressure zones of the home lies a neutral pressure zone. The neutral pressure
zone tends to move toward the largest air leak. The chimney's neutral
pressure zone is above the neutral pressure zone of the house. This creates a
flow of air out the chimney even when no fire is burning. As the large volume of
air is drawn up the chimney, warm air from other areas of your house goes up the
chimney, too. This robs heat from the other rooms and pulls cold air into the
home through cracks around windows and doors that have not been completely
sealed . Sealing the fireplace helps stop the 'breeze' coming from your
doors and windows.
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