Condensation in my chimney

[Scottie]

Been burning wood in my stove that hasn't really been seasoned properly by myself. I try and burn ash, hawthorn, sycamore, cherry and a bit of birch. Normally I get the wood during the year and split it as soon as I can and let it begin to dry out. It doesn't really get a year to dry before I begin to burn it. I have created the problem of condensation in the stack and I have recently had the chimney lined. I haven't lit the stove yet since it was lined last week.

 

We have creasote coming through the walls because of the condensation. My question is to the chimney folk out there, how can we stop the seepage through the walls, and will we just have to grin and bear it and allow it run its course to dry out?

 

Thanks

[niftysteve]

have you had a flexi liner fitted or a liquid lining system

[Alycidon]

Been burning wood in my stove that hasn't really been seasoned properly by myself. I try and burn ash, hawthorn, sycamore, cherry and a bit of birch. Normally I get the wood during the year and split it as soon as I can and let it begin to dry out. It doesn't really get a year to dry before I begin to burn it. I have created the problem of condensation in the stack and I have recently had the chimney lined. I haven't lit the stove yet since it was lined last week.

 

We have creasote coming through the walls because of the condensation. My question is to the chimney folk out there, how can we stop the seepage through the walls, and will we just have to grin and bear it and allow it run its course to dry out?

 

Thanks

 

Creosote is given off in gas form by all woods when they burn. If the temperature in the firebox is not above the combustion point of the creosote then it will condense in the chimney and leave you open to a chimney fire in future.

 

A, The wood you are burning to to wet, the energy within a log is first used to evaporate the remaining water, the rest in used as heat. Not enough heat means to much water.

 

B, Crerosote coming through the wall. You could have used a couple of products the you burnt within the stove that crystalized the tar and caused it to fall back down the chimney. However now you have had it lined then the fumes from these products cannot reach the old tar, so there is not a lot you can do on that issue.

 

 

 

I have been experimenting with my showroom stove this winter burning pop up to about 35% MC. The secret is to use primary air under the fire as well as secondary air down the inside of the glass. Get a good fire burning and as soon as you can get a new log in refuel it.

 

I would recommend that you buy in some logs with a MC no higher than 20% for the remainder of this winter.

 

I assume you have had a stainless steel liner put into the chimney with a stainless steel cowl on top to keep birds, rain and snow out. Quiet a lot of what people come to me with as condensation on a stove installed by others is in fact rain running down the chimney as a result of not installing a cowl. Again use dry wood and burn it hot, you will have no issues with condensation. However you can backfill the chimney with loose vermiculite insulation material if you wish. I do about 1% of my installs with this and dont have issues.

 

Hope that helps.

 

A

[ThrustSSC]

Your 'condensation' issue is much more likely to be rain as Alycidon says, IMHO. Now you're presumably cowled on top that will no longer be a problem. And once the chimney has dried out, the tar and creosote will stay put and stop spreading.

 

The problem it sounds like you have is tar/creosote coming through the chimney brick and mortar, and staining your walls in the living spaces. Your new flue will have dealt with the issue of combustion products getting through, now you need to deal with the legacy. You need to seal that brickwork with an oil-based paint. And that's real oil-based paint, not the modern water-based glosses or eggshells. Seal it well back from the chimney itself, or you may find the problem simply migrates through the plaster and around the sealing coats. And once it's all dried out it'll stop migrating.

 

Hope that helps...

[Nick Watkins]

I was always told by my old chimney sweep to leave the door slightly ajar on the log burner when it's not in use to allow the stack to breathe.

 

Since then I have had the chimney lined and insulated so can't see it being relevant now, I still do it out of habit though.

[ThrustSSC]

Your 'condensation' issue is much more likely to be rain as Alycidon says, IMHO. Now you're presumably cowled on top that will no longer be a problem. And once the chimney has dried out, the tar and creosote will stay put and stop spreading.

 

The problem it sounds like you have is tar/creosote coming through the chimney brick and mortar, and staining your walls in the living spaces. Your new flue will have dealt with the issue of combustion products getting through, now you need to deal with the legacy. You need to seal that brickwork with an oil-based paint. And that's real oil-based paint, not the modern water-based glosses or eggshells. Seal it well back from the chimney itself, or you may find the problem simply migrates through the plaster and around the sealing coats. And once it's all dried out it'll stop migrating.

 

Hope that helps...

 

PS Yes, I know that means redecorating afterwards :-( But it's worth it!

[blades]

Have you insulated around the flue liner? Vermiculite poured in from the top to fill all voids

[Alycidon]

I was always told by my old chimney sweep to leave the door slightly ajar on the log burner when it's not in use to allow the stack to breathe.

 

Since then I have had the chimney lined and insulated so can't see it being relevant now, I still do it out of habit though.

 

Leaving the secondary air control open will do the same thing OK.

 

A

[Al Baker]

I bought a wee stone house in Scotland some years back. While I was busy gutting it, I came a cross Foil backed woodchip wallpaper. The walls were wet behind it. I guess the previous owner wasn't into getting the roof fixed. Anyway, something like that (if it exists outside scotland) might work. You could also batten and plasterboard the affected area. Or maybe give it a few coats of gloss paint before emulsion.

With regard to creosote, I sometimes get it in my flue from burning at low temps. I get rid of it by bunging a few beer cans in the stove and cranking it up until they've gone.

[porky]

We inherited creosote coming through the wall. Cured it by studding and plasterboarding it.