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Issue: 97 February 4, 2005 |
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Education:
Better
Understand Your Home and Those You Sale |
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The
Adventures of Wally Raindrop
Who
is Wally? |
| Chimney
Construction and Safety |
Hello,
Wally Raindrop here. Hope you haven't
forgotten me (Don't remember? Click on
"Who is Wally?" above).
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| Last time
Hilton let me write one of these
little epistles we dealt with Chimney
Caps. At the right you will see what
happened to the not so smart Realtor
who didn't pay attention to the
chimney cap article. When Wally speaks
you had better take heed or my friend
the coon may set up house keeping.
I told you there is much more to a
chimney than the cap and I will talk
about some other issues today. First
lets examine a good example of how you
may not want your chimney to look: |
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You all
did know that old Hilton grew up as a
brick mason didn't you? Well, even in
his finest hour he was not this good.
Yep, this may be a fully functional chimney
although the shape may be a little deceptive.
Chimneys may come in all shapes, sizes
and art forms. It's not necessarily
what the chimney looks like on the
outside. It's about the inside that is
not visible
There are many different types of
chimneys or flues and with different
functions. When we hear the word
chimney we most likely immediately
think of a fireplace. However, there
may be a chimney or flue from your
furnace, water heater, pool heater, or
many other fixtures or appliances
which use combustion to serve a
purpose. |
| The
U.S. Consumer Product Safety
Commission, reports that some
23,600 residential fires in
the 50 states were related to
solid fuel appliances and
equipment in 1996. An
additional 5,500 fires were
attributed to chimneys and
chimney connectors serving
heating systems burning liquid
and other fuels. As a result
of these fires, 130 people
died, 230 people were injured,
and total property losses were
set at more than $184.4
million. In addition there
were a minimum of 119 deaths
from carbon monoxide and at
least 4,700
"injuries" reported
for the same time frame,
though most estimates range
much higher. Wally thinks that
Chimneys are an item you
should be concerned about! |
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Here are the two most common types of
chimneys and fireplaces:
| Masonry |
Manufactured
Metal |
| Masonry
chimneys are usually constructed as
part of the structure and are made of
brick, block or stone with a terracotta
clay tile liner. |
Manufactured
chimneys are made in a factory and
assembled on the building site.
They're usually made from metal and
come in various designs that are
intended to help in the process of
venting and heating safely. |
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What’s
a chimney flue?
It’s a vertical passage way up (and down)
the inside of your chimney. It's also a very
good path for me, little Wally Raindrop, to
get in along with the Raccoon pictured above
if you didn't pay attention to my last
little lesson. Each appliance connected to
the chimney should usually have a separate
flue.
What
causes most chimney fires?
The most common causes of masonry and
manufactured metal chimney fires are
improper installation, improper maintenance
and improper use of the chimney. Are you
paying very close attention. People cause
chimney fires! Constructed, maintained and
used properly, chimneys are safe. Hilton
recently handled an insurance dispute where
a person tried to get a smoldering fire
started in the basement fireplace using a
little gasoline. Results, he ended up in the
hospital for months and is lucky to be alive
with over $200,000 in damage to the
home.
How can I
help prevent a chimney fire in my home?
 | Make sure
the chimney was installed correctly. You
have two choices, educate yourself our
hire a professional. |
| The
chimney should not be too close to wood
framing or insulation. The chimney or
stovepipe should pass through the
ceiling properly.
| Check
routinely for any structural damage to
your chimney. For metal chimneys, look
for corrosion or rusting of the
chimney’s inner layers. Also look for
buckling of the inner seam or collapsing
of the inner lining. For masonry
chimneys, look for cracks in the brick
and the tile inner lining of the
chimney. If your chimney does not have a
inner liner, you should get
one.
| Check
frequently (as soften as twice a month)
for creosote and soot build up. If you
see it, hire a chimney sweep to remove
it.
| Have
annual chimney inspections and
cleanings. How much is your life and
that of your family worth? |
| | |
How
Chimneys Work (this gets a tiny bit
technical, but it will help you understand):
The purpose of
a chimney is to take the combustion products
(smoke and gasses) from the appliance to the
atmosphere outside your home, and at the
same time, to draw air for combustion into
the appliance. This movement of combustion
air and exhaust is called draft.
In essence, it
is the difference in pressure between the
air/gasses inside the chimney flue and the
outside air that creates this movement.
Warmer, lighter gasses in the flue tend to
move upward.
To keep the
pressure conditions favorable, we need a
tall column of warm air inside the chimney,
and cooler air outside. The warm air will
tend to rise, drawing the exhaust from the
appliance out. As air exits the chimney,
fresh air for combustion is drawn into the
appliance.
Factors
affecting draft.
Since draft is a measure of pressure,
chimney draft is affected by pressure
conditions in the house. Several factors
come into play:
-
Adequate
air. First, there must be adequate
air movement into the house to make up
for the air exiting through the chimney.
If the house is very tightly insulated,
the volume of air drawn up the flue will
exceed the volume of air entering the
house, and the house will gradually
become depressurized. With lower
pressure in the house than outside,
there will be a tendency for air to be
drawn into the house from all available
openings including down the chimney.
- Air
movement in the house. Second, air
movement in the house must not interfere
with the chimney. Picture a house with
the upstairs windows open. Warm air in
the house will exit through the open
windows. The entire house then becomes
like a big chimney. As air flows out
through the windows upstairs, air is
drawn from downstairs to replace it.
This is called the stack effect,
since the house acts like a stack,
or chimney. Open windows upstairs are
just one cause. A poorly-insulated roof,
a drafty attic, a tall stairwell, or
anything else that allows a considerable
amount of heated air to exit the house
upstairs could create a stack effect
problem. If the stack effect is
powerful enough, it will overcome the
chimney's upward draft and pull
replacement air (and smoke) into the
house through the chimney.
- Competition
for available air. Third, there must
not be too much competition from other
devices in the house, such as exhaust
fans, dryers, other appliances, or air-exchange systems. If
something else is sucking the air out of
the house, the chimney might not be
powerful enough to overcome it, and
exhaust might be drawn into the house
from the chimney.
- Proper
chimney design. And finally, a
chimney must be designed to accommodate
the volume and type of exhaust being
emitted by the appliances it serves.
This involves correct sizing, adequate
height, proper construction, and the use
of appropriate building materials.
Since the
chimney draft is affected by so many
factors, draft problems can be complicated.
You don't give much thought to your
fireplaces, chimneys and flues, do you.
There are books written on this subject
alone. Unfortunately we simply can't
cover it all here. Chimneys and flues are one very small component of an over all
home inspection. Just one more reason you
need to be very sure the home inspector you direct
your clients toward knows not only chimneys,
but the thousands of other complex issues
related to the home you just sold
them.
For those of you who are interested in
additional information here is the best site
I have visited on Chimneys: http://www.chimneys.com/burnsec/index.html
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Bye Bye
Ya'll, I'll Be BACK (Aren't You Excited?) |
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Thoughts for the week...
Why is it that doctors call what they
do "practice"?
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