I have a fireplace located on the outside wall of my house (the
chimney is brick). Whenever I use it, it it drafts beautifully, and
doesn't smell at all.
However, once the fire stops, and the fireplace cools down, I get an
awfull backdraft, and my house smells nasty for many days after that.
I have a top-seal damper and glass doors (although not too tight
ones). I have them open when the fire is on, and close both when the
fireplace cools down).
I browsed the web, and found out how awfull outside chimneys are, and
how they by design prone to problems similar to mine due to the stack
effect, etc. However I didn't find a lot of advice on how to correct
the issue. This kind of surprises me, since I see lots of houses with
outside chimneys (much more than with inside ones). Do all that
people have the same problem?
Should I forget about it and just stop using the fireplace?
Thanks in advance,
Leave the damper open a bit longer and consider better doors. A hot fire
tends to clean the firebox and lower chimney while a smoky fire adds to the
I had 2 outside chimneys on the last house and only recall a minor problem
on rainy days. But both units had a lower damper.
I actually tried to leave the damper open. This doesn't seem to
affect the problem.
What is considered "better doors"? I have ones from the previous
owner, apparently from Home Depot or Lowes. I can see that they are:
1) Not insulated properly during installation, and
2) Have gaps between doors and around the hinges.
Are the doors supposed to completely stop the air flow?
My glass doors probably block at least 99% of the open frontal area
that they close off. Why would you leave the dooors open when you
have a fire going, that just pulls in cold outside air that you heat
and then it goes up the chimney? Doesn't the fireplace have an
outside air vent into the firebox so that you use outside air for
combustion? If not, you should figure out how to do that, it might
help a lot with stale odors.
My glass doors probably block at least 99% of the open frontal area that
they close off.
I would have said 95-99% so hoffman and I are about as close as newsgroup
posters ever come to agreement.
Had the same problem in my previous house. This didn't *solve* the problem
but did help it.
Thanks, looks interesting.
Did you try it in winter?
Our problem occurred intermittently all year round. Seemed to be worse when
the humidity was high or ashes were left in FP. I used whenever I noticed an
I installed a certified insert, with a stainless steel liner pipe out the
chimney. I built a well fitting "seal" where the metal panel around the stove
fits to the fireplace. The smells only happen now if I run too many exhaust fans
without opening a window.
Exhaust fans can definately cause problems. A furnace without outside air
supply, or a gas water heater can cause problems. Anything that exhausts inside
air from the house, basically.
Some people make a seal to insert into the top of the fireplace after it cools.
A board with insulation on top perhaps, with a stick to prop it up.
Better seals on the glass doors can help.
My parents fireplace has metal screen which operates much as
pulling a window curtain open or closed. Dad made a piece of
panelling, which slides behind the screen. They had cold air
coming down the chimney, and the piece of panelling helps a
lot. Of course, remove before light the fire, and replace an
hour or so after it's believed to be out.
We also have to hold a flaming piece of news paper up the
chimney to start the draft. And keep the fire along the back
wall of the fireplace. Otherwise the smoke goes into the
I had same issue and found unless I spend maybe 1000.00 I could not
get doors that sealed. I have a chmney cap closed by a wire. I took 1"
angle iron and screwed it around the fireplace opening, back in about
3" so it looks normal. I took 4" of R7.2" foamboard and stuck magnetic
tape on the board. When it cools I pop it on the metal and have an
insulated airtight seal. My living room temp went up several degrees
as the open fireplace was allowing in alot of cold air. The doors you
normaly get are for looks and fire safety, not insulating.
My glass doors don't get too cold as long as I close the damper which
is located at the top of the firebox. I have a built-in complete
heatolator unit from Sears, about 15-20 years old. The back of the
unit is closed in with the proper clearances, etc backing to the
garage which is under part of the 2nd floor. So the fireplace is not
exposed to very cold temperatures except for the combustion air input
which itself runs thru a 4" diameter pipe from outside thru the garage
into the firebox. There is also a damper type of control for the
combustion air. We use the fireplace enuf that closing off the glass
doors with a foam insert would be more trouble than it is worth. When
there is no fire and it is cold outside, I really don't feel much cold
coming off the doors, not nearly as much as I get from one window that
is a single pane of glass (haven't gotten around to replacing it with
double-insulated glass yet).
I can heat the whole house on a day like today 32F just by keeping a
medium fire going, which I am doing right now and waiting for the
power to go off as we are having an ice storm here in the western
Chicago suburbs. One tree limb is hanging down touching the telephone
line which is lower than normal due to the ice on it. I would knock
the ice off, but that would just raise the telephone line so that it
is really tight against the tree limb. AS couple of big tree limbs
are atarting to sag toward the power lines that run along the rear
property, but Com Ed said they weren't a problem, so I'm just wait
until something happens and let them fix things then.
COuld be your house is sealed too tightly and it is getting combustion
air from the house. When the fire goes out the partial vacuum created
in the house sucks air back down the chimney. I used to open my ash
cleanout a bit to solve this.
If you're getting a "backdraft" coming INTO your house from the chimney,
that would indicate you have a negative air pressure in the house, not
positive. Normally positive air pressure is needed in house to insure that
furnaces, fireplaces, etc., have a good starting draft. Once there's heat,
the draft will reverse and go up the chimney, so that explains why when you
have a fire it's OK.
I'll bet you have a little trouble and extra smoke problems coming into
the house though, as you're starting the fire, right?
The "cause" is improper sealing somewhere in the house; the net effect is
that more air is being pulled out of the house than can enter it under
equilibrium. Rather than create even worse issues by trying to point out
precisely what to do, I'd recommend you do some research at fireplace web
sites, maybe wikipedia.com, and possible talk to a contractor about it and
see what they think. I think you'll find their assesment about the same as
mine if you explain it the same way you did here.
Here are a few links that'll help you figure things out; they're right up
you alley for the most part. I do NOT recommend or endorse any of the
following links and have NO interest in them in any way. I do NOT recommend
spending money at any of them unless/until you have done your own research
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