14 - Friday, August 25, 1989 - North Shore Nev's

CHIMNEY LINERS

Match home's flue and furnace
sizes as closely as possible

IF YOUR summer schedule in-
cludes home renovation chores,
such as adding insulation to your
home, remember that energy con-
servation can be hazardous to your
health.

For instance, making a house air
tight can result in improper venting
of high efficiency furnaces and
poorly. maintained chimneys, ac-
cording to Jan Donnelly, president
of a manufacturer of flexible and
rigid chimney liners.

“Modern, efficient oil and gas
furnaces give off cooler gases than
their predecessors. if vented into
an older, larger chimney, the
chances of carbon monoxide
poisoning and fire become much
greater,’’ he says.

The problem is caused when to-
day’s cooler exhaust gases enter
older chimney flues where they ex-
pand and cooi to their dew point
before escaping from the chimney.

“One cubic foot of exhaust con-
tains about two gallons of water,”’
says Donnelly. ‘‘During the winter,
this water will freeze and thaw,
causing the brick and mortar of
masonry chimneys to crack and
crumble. In addition, the conden-
sation also contains sulphurous
acids that eat away at the
chimney.’

Flue gases must exit the chimney
at 150°F to prevent condensation.
The solution is to match fiue and
furnace sizes as closely as possible,
to keep exhaust fumes in a gaseous
state. The most efficient way to do
this is to down-size the existing
chimney by installing a proper size
Stainless steel or aluminum liner.

“We estimate that about one-
third of all chimneys in the U.S.
and Canada are experiencing some
trouble releted to improperly sized
venting units. This is largely the
result of the shift to higher effi-
ciency natural gas apgpiiances
which burn at only about 650°F.
Compared to solid fuel {i.e. coal
and wood) which burns from
1,500°F to 2,100°F.

“Homeowners should be aware
of the tell-tale signs of deteriora-
tion: loose mortar, damp spots and
flaking vrick, flue gas odors in the
furnace area and blistering on
walls where the chimney rises,’’
Donnelly says.

Crumbling brick from the
chimney may fall inward, blocking
the flue and causing exhaust fumes
— including carson monoxide gas
— to back up inside the house.

Wood stoves (and fireplaces)
carry an additional potential
danger in that creosote, a highly
flammable residue, can condense
in stove pipes and chimneys, in-
creasing the risk of fire.

Over the past decade, home fires
in which heating appliances were
the source of ignition, increased to
10 per cent of the annua! total,
from 8.4 per cent, according to
Donnelly.

“The human cost of these fires
was 352 injurics and deaths in
Canada in 1437 (the most recent
yeer for which statistics are avail-
atle) and a further loss of $93.7
million in property.’’

Modern, efficiently burning
heating units require a reduction in
chimney size to effectively draw
combustion air. Ironically, im-
proper venting prevents the unit
from operating at its optimum
level, thus defeating its very pur-
pose.

Furthermore, each appliance in
the home should te vented sepa-
rately, matching the type of ex-
haust to a iiner of the preper size
and material. “Under no cir-
cumstances should you vent a solid
fuel appliance together with a gas
appliance,’* Donnelly says.

“Gas furnaces can be vented
safely through aluminum liners,
while oii and solid fuel units re-
quire stainless steel.”’

Missing mortar and loose brick
are obvious evidence of deteriora-
tion. However, there are many
other warning signs. Masons and
heating/ventilating contractors are
specialists in this field. They are
qualified to repair any existing
damage and to prevent further
erosion by installing the most ap-
propriate chimney liner.

To evaluate the state of your
chimney, answer ihe following
simple questions:

els the chimney adequately

supported?

Is the mortar and brick hard
or can you push a knife blade into
it?

eHas the chimney base
deteriorated?

eis there deterioration below
the roof line?

is there combustible material
(i.e. timbers, wall members) within
three to five centimetres (one to
two inches) of the chimney?

Then, examine the flue by look-
ing into it with a light and a mir-
ror, through any available open-
ings. Vertical and horizontal
cracks in the brick — especially at
offsets — can signal danger.

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