Replacing wood stove/interior pipe, need to prevent significant condensation

[tlhfirelion]

Hello everyone. We are thankfully going to replace our old Lowe’s wood stove with another Absolute steel hybrid but there is one issue I need to remedy before installing. Our current stove (see pic) has a serious issue with a lot of condensation dripping down the single wall interior pipe and severely rusting the old stove. Our home is ICF and absurdly well insulated and air tight. We have a very common issue of water actually pooling around the base of the stove during the heat of the summer. I want to prevent that issue but I don’t know what to do to achieve that goal. I’ve posted on this in the past but am finally able to afford to do everything.

Attached is a pic shortly after we installed the current stove 6 years ago. The chimney stack is 7’ of interior single wall and approx. the same double wall outside, all straight up. Would installing a damper along the ceiling that I close in the summer stop the condensation? Would double wall interior pipe help? I don’t want to install a significantly more expensive stove and have it rust out nor do I want this issue to continue. I don’t know what the root cause of this is as I’ve had multiple wood stoves over the years and never had such a significant condensation issue like this.

Thank you in advance for any assistance you are able to provide.

 

[Whitenuckler]

Hello everyone. We are thankfully going to replace our old Lowe’s wood stove with another Absolute steel hybrid but there is one issue I need to remedy before installing. Our current stove (see pic) has a serious issue with a lot of condensation dripping down the single wall interior pipe and severely rusting the old stove. Our home is ICF and absurdly well insulated and air tight. We have a very common issue of water actually pooling around the base of the stove during the heat of the summer. I want to prevent that issue but I don’t know what to do to achieve that goal. I’ve posted on this in the past but am finally able to afford to do everything.

Attached is a pic shortly after we installed the current stove 6 years ago. The chimney stack is 7’ of interior single wall and approx. the same double wall outside, all straight up. Would installing a damper along the ceiling that I close in the summer stop the condensation? Would double wall interior pipe help? I don’t want to install a significantly more expensive stove and have it rust out nor do I want this issue to continue. I don’t know what the root cause of this is as I’ve had multiple wood stoves over the years and never had such a significant condensation issue like this.

Thank you in advance for any assistance you are able to provide.

Have you tried plugging it for the summer right on the roof? Or is that too hard to get to? If you have someone or yourself clean it at the end of the season someone might be up there anyway. I'm not sure how you would remind yourself or someone else not to light a fire.
Maybe put something in the firebox with a sign. I have used 1 inch exterior foam board and you can cut it to any shape.

 

[Rickb]

pop open the connection to the stove then put a plastic bag around it then seat it again. Will block any air transfer. Tho i never bothered. If your pipe is set up right any moisture should end up in the stove not on top.

 

[bigealta]

I used to tape a heavy plastic bag over the top of the chimney in summer before i put a cap on it. I can still get some water down the pipe if it is very windy with rain. This does rust out and eventually ruin a stove so definitely figure out a fix that works for you.

 

[tlhfirelion]

Have you tried plugging it for the summer right on the roof? Or is that too hard to get to? If you have someone or yourself clean it at the end of the season someone might be up there anyway. I'm not sure how you would remind yourself or someone else not to light a fire.
Maybe put something in the firebox with a sign. I have used 1 inch exterior foam board and you can cut it to any shape.

I haven’t tried plugging it that far up but I guess I could. I was contemplating adding a damper up high on a pull chain to close off the warm air as close to the ceiling as possible. Would that help? Thanks for the reply.

 

[tlhfirelion]

pop open the connection to the stove then put a plastic bag around it then seat it again. Will block any air transfer. Tho i never bothered. If your pipe is set up right any moisture should end up in the stove not on top.

The water is somehow getting everywhere so I do need to address it. I’m working on a better flashing set up to start. The condensation is an issue, even with no rain, it’s a headache.

 

[tlhfirelion]

I used to tape a heavy plastic bag over the top of the chimney in summer before i put a cap on it. I can still get some water down the pipe if it is very windy with rain. This does rust out and eventually ruin a stove so definitely figure out a fix that works for you.

I might try that bag trick. Thank you.

 

[Whitenuckler]

I haven’t tried plugging it that far up but I guess I could. I was contemplating adding a damper up high on a pull chain to close off the warm air as close to the ceiling as possible. Would that help? Thanks for the reply.

I think you should modify the stove pipe in any way as it's all supposed to be to code.

 

[oskar470]

Is there an attic space where the chimney goes thru? Is the house air conditioned? There is ambient temperature difference in the pipe and that causes the condensation.

 

[tlhfirelion]

Is there an attic space where the chimney goes thru? Is the house air conditioned? There is ambient temperature difference in the pipe and that causes the condensation.

The stove pipe hits the ceiling “thimble” and goes thru about 16” of attic before exiting the roof. Yes, the house is air conditioned.

 

[tlhfirelion]

I think you should modify the stove pipe in any way as it's all supposed to be to code.

Is the idea of the damper not code? I live where code is merely suggested so I’m not required to do it, but I of course want to be safe. I have all the correct high temp pipe going thru the ceiling and outside, flashing, etc. as well as more than adequate clearances from any combustible surfaces.

 

[kborndale]

Is the idea of the damper not code? I live where code is merely suggested so I’m not required to do it, but I of course want to be safe. I have all the correct high temp pipe going thru the ceiling and outside, flashing, etc. as well as more than adequate clearances from any combustible surfaces.

Your insurance company would not agree that code is merely a suggestion.

 

[oskar470]

You say "......We have a very common issue of water actually pooling around the base of the stove during the heat of the summer...."

If the pipe shown in your picture above the stove is not insulated I would guess that's the problem. During the summer the exterior hot air fills the pipe and condenses inside the house since your house is air conditioned. To verify that, turn off the A/C during a very hot day and see if you still get pooling water around the stove

To my opinion the pipe above the stove should be double wall insulated all the way to the top. In addition, I would assume there is a damper just on top of the stove and this damper should be closed during the summer to prevent hot outside air entering the stove.