What is a furnace/boiler chimney liner?
A furnace/boiler chimney liner is your first line of defense
against poisonous fumes and destructive gasses. It is a protective
material within the chimney flue (the passageway for the smoke
and fumes) that works to ensure that the exhaust gasses cannot
escape from the chimney and into the home. The liner also protects
the masonry chimney from damage caused by these gasses.
Older chimneys were not designed to withstand the problems of
modern furnaces and boilers. High efficiency furnaces don’t
waste energy by sending heat up the chimney. As a result, temperatures
in the flue drop low enough to create condensation. This water
combines with acids in the flue to create an acid moisture which
eats away at the bricks and mortar. Sometimes you will see stains
on the outside of the chimney or stains and peeling plaster inside
the house as evidence of a chimney liner problem.
In older homes that don’t have any liner at all it is possible
to have a very dangerous situation: When the furnace comes on,
the chimney warms up and becomes wet with condensation. Later,
the furnace turns off and the chimney cools down and the moisture
freezes. This freeze and thaw cycle plays havoc on the chimney
and can cause bricks to come loose and fall down blocking the chimney.
If the chimney becomes blocked, carbon monoxide can build up and
have nowhere else to go but into the home. Such a situation can
become deadly if not recognized and prevented.
It would be unsafe to vent a
furnace in this flue:
If there is not an adequate chimney liner,
fumes and carbon monoxide can spread into the house.
What is the solution to furnace/boiler chimney liner problems?
While a fireplace chimney flue requires a stainless steel liner,
we can often use a less expensive aluminum liner with a furnace
or hot water heater that burns natural gas. Once the furnace liner
is installed we can then successfully repair the exterior and crown
of the chimney.