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Location: Minnesota
Posts: 3
Question Insulate and seal a furnace stack in the attic?

Recently I had a home energy audit done. The auditor said there was quite a bit of air leakage where the furnace stack (a round sheet metal stack) comes into the attic. He said I should seal the by-pass in the attic and "thought" expandable foam would be OK. Anyone know if this could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is giving off a good deal of heat in the attic - which is evident by the size of the icicles hanging from my eaves. Is there any safe way to insulate a metal furnace stack? Keep in mind - this is a crawl-space sized attic. I've been up there before and it is very hard to move around in. Thanks!
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Speedy Jim
 
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Default Insulate and seal a furnace stack in the attic?

damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim
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Edwin Pawlowski
 
Posts: n/a
Default Insulate and seal a furnace stack in the attic?


"damncold" wrote in message
...

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?


I'd use fiberglass.

He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack?



Thee is fiberglass insulation made for pipes and stacks. Check with a
plumbing supply house. Comes in about 3' lengths and is curved to fit
pipes.


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George E. Cawthon
 
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Default Insulate and seal a furnace stack in the attic?

Speedy Jim wrote:
damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim

You are too speedy, he is talking about loss from
the living space.
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Speedy Jim
 
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Default Insulate and seal a furnace stack in the attic?

George E. Cawthon wrote:

Speedy Jim wrote:

damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim


You are too speedy, he is talking about loss from the living space.



No. There were *two* separate issues. Here is the second one, as
presented by OP:

"He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic "

It being hard to work in the limited crawl space he has,
insulating this sounded like a losing proposition.
Jim


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George E. Cawthon
 
Posts: n/a
Default Insulate and seal a furnace stack in the attic?

Speedy Jim wrote:
George E. Cawthon wrote:

Speedy Jim wrote:

damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim



You are too speedy, he is talking about loss from the living space.




No. There were *two* separate issues. Here is the second one, as
presented by OP:

"He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic "

It being hard to work in the limited crawl space he has,
insulating this sounded like a losing proposition.
Jim


Ok, I missed that. There is a point in insulating
it. If the attic remains cold he is less likely
to have ice dams form. I'll bet that most of the
heat he see in the attic is from the hole (around
the stack) between the living area and the attic.
So in essence, I agree with you, insulating the
stack in the attic is rather a waste.
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Junior Member
 
Location: Minnesota
Posts: 3
Default

Thanks for all the replies. I did make my way up there and yes, the area around the stack is warm and the snow on the roof above it is melted. I could not see well enough to determine how much space there was around the stack. I would like to stop the stack itself from heating the attic. I've checked at some home stores but no one seems really confident if you can put insulation around a stack or not. And if you could, what kind. Any ideas?


Quote:
Originally Posted by George E. Cawthon
Speedy Jim wrote:
George E. Cawthon wrote:

Speedy Jim wrote:

damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet metal
stack) comes into the attic. He said I should seal the by-pass in the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim



You are too speedy, he is talking about loss from the living space.




No. There were *two* separate issues. Here is the second one, as
presented by OP:

"He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic "

It being hard to work in the limited crawl space he has,
insulating this sounded like a losing proposition.
Jim


Ok, I missed that. There is a point in insulating
it. If the attic remains cold he is less likely
to have ice dams form. I'll bet that most of the
heat he see in the attic is from the hole (around
the stack) between the living area and the attic.
So in essence, I agree with you, insulating the
stack in the attic is rather a waste.
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George E. Cawthon
 
Posts: n/a
Default Insulate and seal a furnace stack in the attic?

damncold wrote:
Thanks for all the replies. I did make my way up there and yes, the
area around the stack is warm and the snow on the roof above it is
melted. I could not see well enough to determine how much space there
was around the stack. I would like to stop the stack itself from
heating the attic. I've checked at some home stores but no one seems
really confident if you can put insulation around a stack or not. And
if you could, what kind. Any ideas?


George E. Cawthon Wrote:

Speedy Jim wrote:
George E. Cawthon wrote:

Speedy Jim wrote:

damncold wrote:

Recently I had a home energy audit done. The auditor said there was
quite a bit of air leakage where the furnace stack (a round sheet
metal
stack) comes into the attic. He said I should seal the by-pass in
the
attic and "thought" expandable foam would be OK. Anyone know if this
could be a fire hazard?
He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic - which is evident by the
size of the icicles hanging from my eaves. Is there any safe way to
insulate a metal furnace stack? Keep in mind - this is a crawl-space
sized attic. I've been up there before and it is very hard to move
around in. Thanks!



Insulating the flue pipe in the attic will have almost ZERO effect
on your energy consumption. Any heat now being lost up there is
being transferred to the roof or whisked out the gable/soffit vents.

Sealing around it to stop air movement from the living space will
be beneficial.

Jim


You are too speedy, he is talking about loss from the living space.



No. There were *two* separate issues. Here is the second one, as
presented by OP:

"He also pointed out that the furnace stack is not insulated and is
giving off a good deal of heat in the attic "

It being hard to work in the limited crawl space he has,
insulating this sounded like a losing proposition.
Jim

Ok, I missed that. There is a point in insulating
it. If the attic remains cold he is less likely
to have ice dams form. I'll bet that most of the
heat he see in the attic is from the hole (around
the stack) between the living area and the attic.
So in essence, I agree with you, insulating the
stack in the attic is rather a waste.





I suggest that you use fiberglass to seal around
the stack where it comes from the living space
into the attic first. ( BTW, you also can stop air
movement by putting a metal collar around the
stack; screw the collar to the ceiling (or the
floor of the attic and use fire caulk between the
collar and the pipe. this is a pretty standard
practice for gas furnace stacks here.)
Then see if there is much heat in the attic. If
you still want to insulate the stack in the attic
then just wrap with a 2-4" blanket of fiberglass
held in place with wire ties. Most stacks can be
as close as 2-3" from wood surfaces, so the
temperature must be well below damaging
fiberglass. If you are worried about doing that
(fiberglass bursting into flame or transmitting
the heat to something nearby) then you better
doubly worry about the wood frame penetrated by
the stack in the present condition.
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Edwin Pawlowski
 
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Default Insulate and seal a furnace stack in the attic?


"damncold" wrote in message
...

Thanks for all the replies. I did make my way up there and yes, the
area around the stack is warm and the snow on the roof above it is
melted. I could not see well enough to determine how much space there
was around the stack. I would like to stop the stack itself from
heating the attic. I've checked at some home stores but no one seems
really confident if you can put insulation around a stack or not. And
if you could, what kind. Any ideas?


I told you what to buy last week. No, you won't find it at home stores, I
told you to go to a plumbing supply house It is used on steam pipe, and
boiler breeching all the time. It can take something like 2200 degrees.
--
Ed
http://pages.cthome.net/edhome/


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George E. Cawthon
 
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Default Insulate and seal a furnace stack in the attic?

Edwin Pawlowski wrote:
"damncold" wrote in message
...

Thanks for all the replies. I did make my way up there and yes, the
area around the stack is warm and the snow on the roof above it is
melted. I could not see well enough to determine how much space there
was around the stack. I would like to stop the stack itself from
heating the attic. I've checked at some home stores but no one seems
really confident if you can put insulation around a stack or not. And
if you could, what kind. Any ideas?



I told you what to buy last week. No, you won't find it at home stores, I
told you to go to a plumbing supply house It is used on steam pipe, and
boiler breeching all the time. It can take something like 2200 degrees.


That's good but at 2200 degrees his stack probably
won't be there to support the fiberglass.


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Stretch
 
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Default Insulate and seal a furnace stack in the attic?

Don't use expandable foam on a flue pipe, it is a fire hazard. Most
rigid fiberglass pipe insulation is good for 800 degrees F. (according
to the data sheets the last time I bought some). There is other pipe
insulation that can go higher in temperature, but why pay for that?
Typically your flue gas temperature will not be over about 300 degrees
F. It depends on how much heat is extracted in the furnace and how
much house air is mixed in at the draft diverter if the furnace has
one. Using sheet metal to block the gap between the flue pipe and the
nearest wood will help block air moving from the house into the attic.
You could also install "B" vent for a gas appliance. It typically does
not need clearance between the flue and adjacent combustible materials.
The B-vent in insulated flue pipe.

Stretch

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Junior Member
 
Location: Minnesota
Posts: 3
Thumbs up

THANKS TO ALL! EXCELLENT INFORMATION! FYI - I've checked the ceiling area around the furnace as best I could - not much I could get to there. I plan to go into the attic and will NOT be using expandable foam. I do plan to wrap / insulate the stack to cut down on the heat it's giving off. I will also check the draft area up there to see if I can seal it off with a metal collar. . Thanks again for all the ideas!


Quote:
Originally Posted by Stretch
Don't use expandable foam on a flue pipe, it is a fire hazard. Most
rigid fiberglass pipe insulation is good for 800 degrees F. (according
to the data sheets the last time I bought some). There is other pipe
insulation that can go higher in temperature, but why pay for that?
Typically your flue gas temperature will not be over about 300 degrees
F. It depends on how much heat is extracted in the furnace and how
much house air is mixed in at the draft diverter if the furnace has
one. Using sheet metal to block the gap between the flue pipe and the
nearest wood will help block air moving from the house into the attic.
You could also install "B" vent for a gas appliance. It typically does
not need clearance between the flue and adjacent combustible materials.
The B-vent in insulated flue pipe.

Stretch
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