Chimneys Q&A Archive
Wood Stoves in A-Frame Buildings
Hi, are there special considerations for wood stoves
in A Frame houses? I am looking for the best installation method.
Thanks so much.
Torri
Hi Torri,
Yes there are some important issues to deal with.
First, don't attempt to place a stove against one of the sloping walls
and run the chimney out through the wall/roof far down the slope. If you
try that you'll end up with a very tall chimney outside the building and
providing stability will be difficult if not impossible.
You do need to penetrate the sloping roof in order
to keep the venting system inside, but do it near the peak. By far the
best approach is to locate the stove near one of the gable ends and
mount the chimney in the roof just below the peak. That will keep the
venting system mostly inside the building where it will stay reasonably
warm and will provide the most stable, least ugly chimney installation.
It will also mean you can do the installation from ladders instead of
scaffolding.
John
Boosting efficiency with a flue pipe mounted heat reclaimer?
I'm curious whether there are after market secondary
heat exchangers available as accessories for residential use to be used
to upgrade older pre-high efficiency wood furnaces. I'm just trying to
find a way of harnessing those hot flue gases before they all escape out
my chimney. Is ther anything short of actually buying a new furnace? Our
old one still works but is extremely inefficient and sends a lot of hot
gases up the chimney (especially in the coldest weather when we've got a
large fire going.
Kevin
Hi Kevin,
Retrofit flue pipe mounted heat reclaimers used to be
popular until it was learned that all they do is plug up with creosote.
In Canada they are banned outright because of the hazard they represent.
Advanced technology, high efficiency heaters don't achieve higher
efficiency by extracting more heat from the flue gases, but by burning
the wood more completely. Moreover, the chimney is the engine that
drives a wood combustion system and it needs heat to work. You'll boost
efficiency more by concentrating on burning the wood completely without
smoke than by lowering flue gas temperature. You'll get higher
efficiency by using these
tips.
John
I want to buy
chimney parts online
Hello!
First off, this is an excellent site!!
I especially enjoyed the installation section as well as the
q&a! One question I have is one that didn't get answered on a
q&a -- can you please direct me towards companies (Canada or US)
that offer online sales/info? I
have a feeling the two places I've been able to locate in my area
(western New York) are charging exorbitant prices.
Any help you can give me would be greatly appreciated!
I am getting ready to install a Vermont Castings stove in my
home, which has an 8" flue, and will need a ceiling support kit as
well as 6' of chimney pipe. Thank you very much!!
Terry
Terry,
We do not recommend online purchasing of something as major as a wood
heating system.
You
are getting ready to purchase a VC stove so you must have seen one -
probably in wood heating specialty shop. Had this shop not existed (as
would surely be the case if everyone shopped on line) you would not have
had the opportunity to even touch one.
I think this is the point. If you wish to explore the detail of a
wood stove, or ensure that the chimney and flue pipe you're considering
are of appropriate quality for you, then a "bricks and mortar"
shop is a basic requirement. Stores,
display models, sales personnel, installers, home visits, and so on all
cost money. I'm not saying that the shops are perfect, but if you're
finding that more than one shop is too expensive for you, then maybe
they aren't all wrong, maybe that is the going rate.
VC
makes a quality EPA certified and relatively expensive stove and I
wouldn't shy away from getting it locally. In fact we'd strongly
recommend it. After all, you will need the local shop for any warranty
work or as a resource over the years.
Cal
BBQ starter
as a chimney primer?
Hi!
On occasion my basement will fill with smoke when I try to light
a fire - fortunately, this doesn't happen too often, even
though the woodstove is located in the basement and the metal chimney
runs up the outside of the
house from the basement
(lucky me!).... Anyways, I was wondering if it would be okay
to use one of those
electric BBQ starters to warm
the chimney up? (fyi - the
kind of electric BBQ starter I'm talking
about is a coil of metal that gets red hot when plugged in).
Thanks!
Rich
p.s. I love your site &
visit it often!
Hi
Rich,
I
suspect an electric BBQ lighter might work, but it is rather energy
intensive and maybe time consuming.
And depending on how powerful your backdraft is it might not even
work because the rush of cold air coming down the chimney prevents the
hot air from going up. I
have heard of people having success with hair dryers, usually pointing
them up a chimney cleanout door, because the fan helps to drive some hot
air upward.
But
the normal approach to correcting a cold backdraft before attempting to
light a fire is to open the closest window or door.
This neutralizes the negative pressure due to stack effect that
sucks cold air down the chimney. In
most cases with the window or door open, the chimney flow will turn
around immediately. Once
the fire is lit and a little heat gets into the chimney, you can close
the window or door.
Try
the open window approach. It
tends to be quicker and consumes no energy except for a little heat
loss.
Regards,
John
Chimney
Failure
I
have a franklin stove in my basement, which is in the new addition of my
home. The chimney is stainless, triple wall and runs inside the house
along the outside wall. I have a terrible problem with downdrafts, until
the chimney warms up. The new addition is not as tall as the old section
of my house, so the chimney is a lot lower than the peak of the old
section. I've seen when it really got cold that the chimney above the
stove has been white with frost and the damper frozen solid.
Should I raise my chimney up or what?
I
would really like to use my stove, but my wife hates to get up in the
middle of the night to smoke detectors and a house of smoke when the
fire burns out.
Any
ideas will be much appreciated
Thanks, Steve
Hi
Steve,
You
are suffering from a classic type of chimney failure. You have diagnosed
it exactly right. At standby with no fire in the stove, your house acts
like a better chimney than the chimney. That is, the stack effect
created by the warm air in the house creates a slight negative pressure
down where the stove is and because your chimney is shorter than the
house, it cannot compete, so it flows backwards. The phenomenon is
explained here.
It
is just plain chimney physics that is working against you. The only
sure-fire reliable way to fix the problem is (believe it or not) to
change the relationship between the chimney and house by moving the
stove to the part of the addition next to the tall part of the house and
run the chimney up through the warm space. This will make the chimney
outperform the house as a chimney when it gets cold outside.
Just
raising the chimney might not work, in fact there is a good chance that
it won't, mainly because heat loss in a tall chimney exposed to the cold
is so great that the chimney still can't compete with the house. A
theoretical alternative is to 'trick' the chimney into thinking it is
inside the house and at the same time raise it to be taller than the
house. This would involve building an insulated chase around the
chimney.
But
your chimney is air-cooled, which means it will be cooling itself,
whether you have a fire on or not. I have for many years ranted about
the stupidity of air-cooled chimneys, and your case is a good example of
why they should never be used. The only benefit of an air cooled chimney
is that it is cheap. But it is a truly lousy chimney.
Filling
the house with smoke in the middle of the night is just totally
unacceptable, not to mention hazardous. If that were my system, I'd take
it out and start again. And I'd use a solid-pack chimney.
John
Fireplace
Chimney Problem
Hello.
I have a problem with the chimney for
my 40-year-old split-level house in Toronto, Canada. The chimney is
outside the house and has three flues (2 for two fireplaces [main floor
and basement], 1 for natural gas furnace/water heater). The chimney has
been rebuilt by a previous owner above the roofline once before. The
bricks are spalling above the roofline and breaking apart. We have
installed glass doors on the main floor fireplace to prevent smoke from
escaping into the room. We currently don't use the basement fireplace.
I am planning to
have the chimney replaced above the roofline with matching
bricks, new crown, rain
cap and install a stainless steel chimney liner for
the furnace. While we
get this work done I was wondering what we could do to make the
fireplaces more functional? The chimney is on the lower half of
the split-level -
should the height of the chimney be higher than the roof of
the taller side of the
split-level?
Would you
recommend installing a new hearth? Will the basement fireplace ever be
able to be used practicably or would it be better to convert to gas? Is
it feasible to expect that we not need the glass doors, as they do not
allow the heat to escape?
Sorry for all the
questions but I hope you can help.
Thanks, Darren
Hi Darren,
This chimney has
both of the worst possible characteristics. First, it runs up outside
the house. The problem is explained in some detail here,
and the chimney
penetrates the house envelope below its highest level, which is
explained here.
There is no good
solution because both problems are created by the relationship of the
chimney to the house. You're not alone; these problems plague North
American housing.
By all means,
install a liner for the gas furnace (frankly, I'm surprised you haven't
had serious health problems from combustion spillage from it already).
Better still, replace the vertically vented gas furnace with a
condensing or sidewall vented one so there is less risk of exhaust
spillage into the house.
As for the
fireplace, considering you are in a city, you might want to consider a
direct vent gas fireplace insert; do not let someone talk you into a B
vented insert, which tends to be a little cheaper. If you want wood and
you want heat, install an EPA certified fireplace insert with a full
liner. I would suggest you forget about glass doors or an open
fireplace, unless you don't highly value your health and safety.
John
Outside
chimney causes problem?
I just bought a home with a 40',
metal, outside flue for the fireplace. It's in
Vermont, USA. Am I in trouble from the get go here?
From what
I've read, I have two things working against me.
1. The flue is outside.
2. It gets to -15 deg F here sometimes.
Any thoughts, help, leads?
Hello,
I think your assessment is
correct, based on simple physics. When the temperature in the flue falls
a few degrees below room temperature, the house will begin to function
as a better chimney than the chimney, and air will be sucked down the
chimney by the negative pressure low in the house due to stack effect.
The actual frequency and severity of cold backdrafts in any given system
depends on a lot of factors, but the taller the system and the colder
the weather, the stronger the backdraft and the harder it will be to
correct.
Some people recommend installing
a chase around the chimney to keep it warm, but I've seen enclosed
chimneys backdraft because the chase leaked cold outside air and
because, without heat input from the house, even the inside of a chase
will eventually cool. If you have a very strong backdraft, I wouldn't
recommend a chase, unless you want to spend a lot of money on it.
I would investigate
re-installing the system inside the house. I know that sounds
outrageous, but it can, and has been done. On the other hand, if this is
a cheap factory-built fireplace, then its poor performance wouldn't
likely justify the expense, even if it worked to its potential. You
could save up your money and install a good EPA certified fireplace and
be able to view the spectacular fire and heat a good part of the house
with it.
But, I guess the best thing to
do is try it this coming winter and see how much of a pain it is to live
with. With a system like yours, with a high potential for strong
backdraft, my worry is that, even if you could get a fire burning, as it
recedes to a coal bed the system could go into a hot backdraft and fill
the house with smoke and carbon monoxide. This is why correcting a cold
backdraft by temporarily opening a nearby window to neutralize stack
effect is sometimes not such a good idea.
Good luck with it.
John
Chimney
Height and Draft
Could you tell me the right way
to draft a chimney?
Is the higher the better or the lower height
or how high above the roof should it be?
Thanks, Keith
Hi Keith,
The chimney should extend at
least 3 feet above the roof surface it penetrates and 2 feet higher than
any roofline or other obstacle within a horizontal distance of 10 feet.
Two things determine chimney
draft:
1. chimney height
2. flue gas temperature
Taller chimneys make more draft,
but chimneys exposed to outside cold don't. See our section on chimneys.
Hope this helps.
John
Proper
Height of Flue
We
have inherited a good woodburning freestanding fireplace to install in a
section of our home but we don't know how high the flue should be. The
flue outlet is around 22cm square. The hearth/grate is 80 x 50 x 50 cm.
The room has a flat roof about 2.7 metres from the floor. Is there an
equation to calculate height and size of flue needed? We don't want a
very tall flue unless its is absolutely necessary as we get high winds
in winter and want to avoid excessive bracing. Your help will be
appreciated
Felicity
Hi
Felicity,
First,
the top of the chimney must be at least 1 metre above roof level to
prevent excessive turbulence. Secondly, a good rule of thumb suggests
that system height from hearth level to the top of the chimney should be
at least 4.6 metres. It looks like you'll need at least 2 metres of
chimney projecting from the roof. Flat roofed single-storey buildings
are always a problem with chimney height, but I would strongly
recommend meeting the 4.6 metre objective to help prevent smoke spillage
into the house.
John
Shared
Flue?
Can a
woodstove share a central single flue masonry chimney with other natural
gas appliances (boiler furnace and water heater)?
Thanks,
Paul
Hi
Paul,
In a
word, no. Most codes prohibit co-venting wood and gas, and for good
reason: their draft requirements are entirely different and
incompatible. The draft hoods on the gas appliances bleed off draft to
the point where you could hardly get the stove to run at all, and it
would smoke like crazy if you opened the door. Gas appliances prefer
almost zero draft at the burner and wood stoves like lots of draft.
Ideally
a stove has its own chimney. And besides, a wood stove should never be
put in a furnace room. Wood stoves are space heaters and so should be
installed in the space to be heated, not hidden away someplace in the
basement.
John
Suppliers
of Chimneys
Hi,
We're
interested in installing a woodstove and are wondering what places
(online, presumably) are best for us to learn about and purchase the
stove pipes we will need. Is there possibly a Canadian company, where we
might get a better deal with a favourable exchange rate?
Thanks,
Lisa
Lisa,
When
you say stove pipes I assume you mean chimney, as distinct from the flue
pipes that run between the appliance flue collar and the chimney. I
think you should read our chimney
section before going any
further.
Price
should not be your first concern – safety is what is important.
By the
way, I have never seen anyone, including me, install their first chimney
perfectly. Anything less than perfect might not be safe. I would
strongly recommend that you ask the most experienced person you can find
to give you a quote, then take it from there.
Yes,
there are Canadian companies and Canadian suppliers all over the
country. I don't know why you are concerned about exchange rate. People
in Canada rarely install US chimneys, unless they are part of a
fireplace.
John
Money
Saving Wood Stove Chimney? NOPE!
Hi, I
am planning on installing a wood stove this fall and have a question on
the chimney. I will be installing the chimney in a 25 foot tall framed
chase with inside dimensions of 18 inches by 60 inches. A chimney
installer informed me that I could use a stainless steel liner with a
zero clearance (some sort of fiberglass wrap) instead of the costly
triple insulated stove pipe. This sounds great to me if it is an safe
substitute for the stove pipe.
Your
response is greatly appreciated.
Thank You,
Scott
Scott,
The
plan sounds hazardous to me. Are you sure your chimney installer wasn't
thinking about relining a masonry chimney? It is inconceivable that any
responsible installer would suggest that you could install an insulated
liner in a framed chase, considering the result would likely burn the
house down in short order. These are liners, not chimneys; they need to
be installed in a brick enclosure.
I do
hope you reconsider. Your plan to save money sounds extremely dangerous
to me. If you value your house and your family's safety, save up your
money and do the job right. Maybe you should seek out someone else to
advise you.
John
Adapting
Chimney Sizes
Hello,
I've
taken over a "hippie homestead" in Manitoba, and in order to
get insurance I'm going to have to upgrade the chimneys to the
"2100" type (2-inch insulation). Fair enough - I'm all for
safety!
The
main heater is a Triumph with an 8" collar which has been adapted
to a 7" chimney. (The stove had a label, which is now gone, so I
can't offer specifics.) I may want to, or have to, replace this stove as
well, as I would think there are better designs available now, and I'd
like to keep emissions to a minimum. Something EPA certified or
whatever.
It
seems, from a cursory investigation (there are no serious stove dealers
within 200km of here) that newer stoves most commonly have 6"
collars. Maybe this impression is skewed due to the small data sample.
;-)
I
don't want to put in a shiny new chimney that's inappropriate for the
present stove or a later stove acquisition. The two goals may be
incompatible.
Question:
Presumably
it's best to have the same chimney size as the stove collar. If forced
to adapt sizes, which is the lesser of two evils - large stove into
smaller chimney or visa versa? (If nothing else, this will tell me
something about the quality of the existing situation.)
My
technician's guess (I've no experience in wood heat systems) is that, to
a point, a smaller chimney would have greater flue-gas velocity and be
less prone to creosote accumulation, even though at first blush the idea
of a slightly oversized chimney is intuitively appealing to the
neophyte. One way or the other, I suspect that if the size difference is
too great, one eventually gets into trouble of a different kind.
I'm
thinking I should bite the bullet and buy stove and chimney at the same
time, but as I know so little and the suppliers are at such a distance,
I don't want to rush into this. Meanwhile the nights are getting chilly.
BTW,
I'd love to hire a qualified stove supplier / installer to take care of
this but they're not easy to find here, and I shudder to think what it
would take to get one out here from a distance. When you ask about
installers, people look at you as though you're from Venus. The idea
that you wouldn't put in your own chimney is borderline bizarre to them.
But they've grown up doing this stuff, whereas I've grown up with
thermostats. ;-)
Cheers,
Scott
Scott,
Your
intuition is right. Better to use the smaller 6" chimney. Best to
install a new EPA certified stove with it, but barring that use the
8" Triumph on the 6" chimney, adapting from 8" to 6"
at the bottom of the chimney (ie use 8" smokepipe to the chimney
base) for pretty much all the reasons you mentioned.
For a
list of certified installers in your area check with WETT
Inc. And of course our site may be of some assistance.
Cal
Scott replies:
Cal,
Thanks
very much indeed. Just yesterday the insurance company in question
confirmed this as well.
The
old Triumph doesn't seem like a bad stove, though I know a newer unit
would be a good investment. I've just moved in here though, and I'm
trying to spread the cost of upgrades out a bit! That much more
important not to close doors on myself.
Thanks
sincerely for your help. I'll check the list on the web site, for sure,
but I'll be stunned if there's anyone in the vicinity.
Cheers,
Scott
Smoke
Pipe through a Ceiling
We are
building a cabin, and we would like to put a wood stove in the basement.
I know that this is not the recommended method, but not only do we need
to heat the basement, but our experience with wood stoves is that it
usually gets too hot in the upstairs sleeping area, and we would rather
lean to the cooler side.
My
question has to do with chimney pipe. I looked through the literature on
your site, and I noticed that the maximum distance that you can run
black stove pipe is ten feet. Considering the huge cost difference
between black stove pipe and double wall insulated standard chimney
pipe, and the fact that we need to run pipe 37 feet up to our cathedral
ceilings, I am curious why we can't use regular black stove pipe for
most of the 37 feet. Is this a matter of structural integrity, creosote
buildup, getting burned by touching the pipe, or what?
Any
help would be greatly appreciated.
Hello,
Your
experience with wood stoves may be like my experience with computers....
a bad experience with inferior equipment run by a novice. <G>
Ceiling
fans would certainly help in making the entire upstairs just about the
same temperature if you were to put the stove in the living area.
As the
site says there are "chimneys" and then "smoke pipe"
that connects the stove to the chimney. The chimney must go to the room
where the stove is located. So if you have the stove in the basement,
the chimney will start in the basement ceiling and rise up through the
house then through the roof. The smoke pipe would connect the stove to
the base of the chimney in the basement ceiling. So the smoke pipe will
be very short. You'll have no creosote buildup.. especially if you use a
decent stove (one which is EPA certified).
Should
you do as we encourage and put the stove in the upstairs, then you could
use "double wall smoke pipe" to join the stove and the base of
the chimney up in the cathedral ceiling. (37 feet..that has to be one
steep pitch roof on that one. I've seen ceilings 20 feet high but 37' is
almost double. Some house!). The savings on the chimney would no doubt
pay for a quality ceiling fan with a long downrod.
The
reason you can't use ANY smoke pipe..single or double wall ..on your
proposed basement installation is
-
smoke pie can't pass through a floor, wall or inside any concealed area
-
structural integrity
-
creosote buildup
-
getting burned when touching the pipe
-
it's contrary to building code. The house won't pass code leading to
mortgage problems
-
it
violates the building code so you'll get no home insurance.
In
short don't consider this. Enough people have died from forging their
own path installing their own woodstove.
Have
you talked to a local specialty woodheating retailer / installer
certified for your area? That might be your best bet.
Cal
Chimney
Flashing Through a Metal Roof
I am
installing a chimney in a cabin and want to know the right equipment to
use. Installing
a wood stove under vaulted ceiling. The stove pipe is 6" and
the roof pitch is 10/12. I have an idea of how this will work but the
details are not clear.
What
about the flashing and a ribbed metal roof.
Thanks, William
Hi William,
The
flashing will work fine. Many people cut the hole in the roof and
install the flashing from UNDER the roofing. If in doubt talk to the
metal roofing propel or get a certified installer to help.
Cal
Flue Temperatures
I'm
attempting to find the usual operating flue temperature ranges of
woodstoves and fireplaces. Also if clay liners have a tested
operating temperature.
Thanks,
Miro
Hi
Miro,
Flue
temperatures are highly variable because of differences in appliances,
venting systems, fuel and operating conditions, but the range would be
from ambient up to about 2100°F. A system operating normally will
run between 200°F to 1000°F, depending on where and when in the burn
cycle you measure it.
The
clay liner standard only says that they must not soften at 2100°F.
There is no performance test for clay liners. They tend to fail
because of thermal shock caused by rapid temperature changes like those
that happen during a chimney fire.
John
ODOR BUSTERS PLEASE!!
I have a "heat-a-lator"
type fireplace installed in the basement of my single story home. The
chimney is a masonry type with clay liners and brick exterior on an
outside wall. The liners are 12" as recommended by the fireplace
manufacturer.
I didn't use the fireplace for many
years after it was installed until I finished the family room in this
area. After the first fire I burned and the chimney had cooled down- I
had a very strong sooty smell enter my fireplace and family room from
the chimney-even with the damper closed! The chimney worked properly
while the fire was started and burning. It had plenty of draft and is
covered at the top with a chimney cap.
My question is: Do I just need to
burn more fires to "condition" the chimney to burn out excess
moisture, etc. that may have settled in over the many years of not being
used? and Are there any chemicals that can be used in the fireplace to
help eliminate these odors? (I know after reading your articles that my
main problem is the chimney is located on an outside wall and is not
insulated)
Any comments would be appreciated-
because I love a burning fire and no odors afterwards and my wife said
divorce court was next if those ghostly odors entered the house again.
Thank you!
Ron
Ron,
I'm sorry to say there is no simple solution to your problem because it
is, as you say, caused by the relationship between the chimney and the
house. You can use baking soda or equivalent to reduce the smell, but
this only works if you clean the system thoroughly and then don't use it
any more. Here are some options;
-
install a sealing damper
at the top of the chimney to stop the backdraft between fires (Lymance
and Locktop are popular cable operated brands) (fireplace throat
dampers don't seal well at all)
-
install a fireplace insert with
a full stainless steel chimney liner; this will reduce backdraft
volume and intensity, convert the fireplace to a serious heater and
the chimney liner will tend to isolate the flue from outside cold.
Those are my best suggestions. Good
luck with it and I hope it doesn't end in divorce.
John
What's best: masonry or metal chimneys?
I want to know what the lifespan
would be for an outside the house woodburning chimney made of block and
tile as opposed to insulated stainless pipe.
Hi,
The life span of a masonry chimney depends a lot on how it is used and
maintained. A severe chimney fire can blow the tile liner
instantly and a failure to maintain the cap or crown every year or two
can allow water in. If you live in an area with freezing
temperatures, this can lead to rapid deterioration. Well built and
maintained, a masonry chimney can last a long time. Note that
concrete block shells are not nearly as good as brick because a) they
absorb water and break up with freeze/thaw cycles and b) they are less
stable because there are fewer interlocking joints that key the
structure together. On balance, of all the chimneys that are
acceptable under building codes, a concrete block chimney is the
worst. The fact that you intend to put it outside, which we
strongly discourage, makes it a truly lousy option.
Metal chimneys are well proven and
most have parts warranties. They tend not to need the same level of
maintenance as masonry in order to last a long time.
In short, either option can be
effective, although on balance, we tend to favor metal over conventional
masonry because it has some insulation to keep the liner warm.
John
A question
about steel chimney liners
Hello,
I found your site helpful and interesting. Our home in Massachusetts is
entirely heated by wood. The house is very well insulated, and it is
only 15 years old. I had the local chimney sweep come to clean,
and he says we need a steel liner installed inside our chimney -- for
about $3000 (two flues). We do normally burn with the choke pretty
tight, so it's not very hot in the chimney. But I am surprised
that such a young house would need that kind of repair. What is
your take on steel chimney flue liners? How do I get an unbiased
opinion?
Andy
Andy,
Stainless steel chimney liners are widely used and have been for almost
twenty years. They are a great way to upgrade failing masonry
chimneys. Masonry chimneys can fail in as little as three years,
depending on how they are used. I would recommend that you get
another liner estimate, just to make sure the price you have been quoted
is fair. Choking down woodburning equipment is the main way to
destroy chimneys, both by being the main cause of chimney fires, and
also by permitting water condensation in the chimney, which is really
destructive. You should try to avoid smoldering fires because of
the damage they do to your system and to the environment.
John
Connecting to a two flue chimney
I would like some
info. on connecting wood stove to my chimney, which has two inserts.
I already have a gas
furnace in one of the inserts, so can I put a woodstove in the other
one?
Thanks, Beth
Beth,
To get the terminology correct, you have a chimney containing two
flues which are the holes through which flue gases flow. Chimney
liners (not inserts) surround the flues.
In answer to your
question, yes, you can connect a wood stove to the other flue, provided
it meets code requirements. You really need some local assistance
to make sure the connection would be effective and safe. Chimney
sweeps are good at checking out existing chimneys.
John
Dear Sir:
In the past 2-3 months we have been having problems with our wood
stove.
It is located in our basement.
We have been awakened in the middle
of the night to the heavy smell of creosote.
My husband has cleaned the flue and replaced the pipe from the
stove to the flue. We have
had the stove for 3 years now and this is the first time we have had
this problem. Also, since he replaced the pipe this last time, it is
dripping creosote where the pipe fit together.
Thanks for your help.
el
Hi el,
It is difficult to diagnose this kind of problem without seeing the
system and the house, especially since you haven't given much
information. It sounds like
you are suffering a cold backdraft, normally linked to installations in
which the stove is installed low in the house and the chimney runs up
the outside wall. See The
evil outside chimney
If someone in your household likes
to sleep with their bedroom window open a little for fresh air, this may
be the problem. Any leaks
high in the house will make a cold backdraft more likely and more
powerful. I would strongly
recommend that you get a chimney sweep or stove/fireplace specialist to
inspect the system and advise you.
Also, since you report dripping
creosote, it is likely that the stove is being allowed to smolder.
Low flue temperatures due to smoldering is a common reason for failures
to vent smoke properly. Check out all the tips on stove operation here.
John
Joe's got an outside chimney – NOW what can he do?
So I blew it and built a metal chimney outside the
house enclosed in a frame chase. I assume I will have the backdraft
problems you spoke about in your "evil
outside chimney" paper. What can I do now? Would putting some
kind of blown in insulation into the chase around the pipe help?
Thanks, Joe
Joe,
Yes, your system will be prone to cold back drafting, but before
responding I need to deal with the issue of insulation around the
pipe. You wrote: "Would putting some kind of blown in
insulation into the chase around the pipe help?" If you
really did that, rather than just fill the spaces between the framing
studs of the chase, you would likely burn your house down. The air space
around chimneys must be maintained or they will overheat. Please do
not blow insulation into the cavity. If you want to insulate, only
put it between studs. Also, insulation and air barriers in chases must
be contained by sheathing to prevent them from heating up and falling
against the chimney.
A number of things affect how strong cold backdrafting
can be, and how big a problem it is, such as:
- how cold is your climate?: the colder the climate
[or weather], the stronger the backdraft; houses in Canada and
northern tier US states suffer powerful backdrafts; people in
southern states don't [but, of course, they have other problems]
- how tall is your house and chimney?; taller houses
and chimneys backdraft more aggressively; this is why basement stove
backdrafts seem stronger than main floor stove backdrafts
- where are the leaks in your house?; the higher the
leaks, the stronger the backdraft; if you have a leaky attic hatch,
lots of high level recessed light fixtures, forced air heating
ductwork in the attic, or you like to sleep with the second floor
bedroom window open, you'll have stronger backdrafts
The really bad thing about outside chimneys is that
the remedial measures are either ineffective or unappealing or expensive
or all three,
which is why we tend to be strident about not putting them there in the
first place.
Consider the following comments in the context of the
three points made above.
Insulating the chase might help some, but
a large component of heat loss from typical chases is from leakage, so
sealing it [including top and bottom] is at least as important as
insulation. The only way to really fix an outside chimney is to trick it
into thinking it is inside. That would mean a chase that is the same
temperature inside as the house is so the chimney stays warm enough to compete
with house stack effect. With a really well sealed and insulated chase,
you could vent it into the house, with a couple of passive vents at top
and bottom of each storey, so that a convection current would keep the
inside of the chase nearly as warm as the house. That strategy is the
only one sure to work, and then only if it is done well
On the other hand, if your climate is reasonably mild
and your house is reasonably short and if its leaks are relatively low
and you keep fires burning most of the winter and you burn the wood
bright, hot and clean, you might never have a problem with cold backdrafting.
John
When it's windy, we have a smoky house
We installed a new
woodstove with an existing chimney when we moved into our house three
years ago. Last spring and this winter, we have been having
problems with smoke coming into the house through the stovepipe joint
where it enters the ceiling. When it first happened last spring,
we thought it was possibly because of a pressure inversion. This
winter, however, we seem to have a smoky house any time there is a wind.
Our chimney is straight, inside in a one story addition to a one and one
half story house. We clean the chimney frequently (approximately 5
or 6 times/winter). Do you have any diagnosis for the problem,
where we can get help, and how we can fix it? We didn't have this
problem the first winter we were here.
Thanks, Ed
Dear Ed,
Problems of this kind are so complex that I could spend a long
time writing to you about possible contributing factors. I can't
do that. But here are a few ideas.
1. A chimney installed in a single storey section
of a two storey house has to compete as a stack with the house, especially
when no fire burns or when chimney temperatures are low like when the
fire smolders. This may not be the main cause, but it weakens the
chimneys ability to flow air and gas up under all conditions.
2. You need to pay attention to which wind
direction leads to the problem. If spillage happens when wind
blows from the single storey side, you need to look for leaks on the
downwind side of the house on the two storey side, especially high level
leaks like open second floor bedroom windows or a leaky attic hatch.
This situation can depressurize the house and suck flue gases down the
chimney into the room.
3. Smoldering fires are a key cause of this type of
failure. Make sure that you burn small, hot fires and don't let
the fire smolder. The wood should be flaming until it is reduced
to charcoal.
4. If there is no cap on the chimney, get one; open
chimneys are extremely vulnerable to adverse winds. Raising the
chimney might help to get the top of it up out of a zone of positive
pressure caused by a wind effect.
Ideally you could contract with someone who can
come to your house and diagnose this, but such people are hard to find.
Check first with local chimney sweeps or long-time stove and fireplace
retailers.
John
Stainless
steel liner in a masonry fireplace chimney
What
options are available for fireplace flue repair?
We are working on a project where there are two existing
fireplaces, roughly 75-80 years old. The owner would like the
fireplaces restored. Can
stainless steel liners be used on wood burning fireplaces?
Jim
Hi
Jim
Yes they can, but it is not an elegant solution because the connection
above the throat and damper are difficult to do and rarely done well.
Since we at woodheat think wood should not be wasted just to
watch it burn, but should provide an energy benefit by delivering heat
to the room, we would recommend the installation of a fireplace insert
with a full stainless liner to the top of the chimney.
In this case the liner is sized to the insert, not to the
fireplace, and the connections can be secure and permanent.
An additional benefit of an insert is that it would improve
resistance to smoke spillage into the room and reduce outdoor air
pollution from the fireplace. This is the only environmentally
responsible solution, in our opinion.
If
your client insists on retaining the conventional fireplace for
historical or nostalgic reasons, a far better solution than stainless
steel is a solid-set poured-in-place lining system.
This insulating cementatious material greatly improves the
structural integrity of the chimney and improves performance by
insulating it.
You
need to find a supplier of SolidFlue, Arens, Golden Flue, Supaflue and
there may be a couple of others that I can't think of at the moment.
Chimneys sweeps can usually tell you if there is a local
supplier.
Regards,
John
Jim responds:
John - Thank you very much for your response. It certainly helped quite
a bit.
A fireplace cannot share a chimney
I bought an old
house in Philadelphia. The heating system is gas, hot air.
There are two chimneys. One vents the heating system and air
conditioning; that one is in the living room. The other vents the
hot water heater. I would like to add a fireplace in the living
room. I would prefer wood. It would need to be very small,
as the living room is 14 X 16.
Is there some way to
utilize the chimney that vents the heating system? If not, how
expensive would it be to install a new chimney for a wood burning
fireplace (ball park figure is OK). The house is two stories and
very small.
Am I better off with
a direct vent gas fireplace?
Any advice would be greatly
appreciated!!!
Sincerely,
Susan
Susan wrote,
“Is there some way to utilize the chimney that vents the heating
system?”
No, you can’t use
a chimney for both a fireplace and heating system.
There are many
factory-built fireplaces on the market of all shapes and sizes.
They don’t need a foundation, can be put almost anywhere and routing a
chimney up through the house is done all the time without problems.
You need to visit a few fireplace retailers, see what they have and what
they have to say.
“Am I better off
with a direct vent gas fireplace?”
We are not the right
people to ask about gas fireplaces. Since most everyone else will
advise you to go gas, including most fireplace retailers, I will suggest
that if you want a real fire, the only option is wood.
Regards,
John
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