The relationship between wood-burning stoves and condensation is a tricky one, though some instances are more serious than others.
Let’s start with what ought to be the least severe example of condensation on a stove…
Condensation on the outside of the stove
Condensation on the outside of the stove body is usually an indication that the air in your home is humid and is condensing when it comes into contact with a cold surface (that’s why you will normally spot this if your stove is out of use for a few days).
If you already experience condensation in your property (on windows, for example), this is just an example of the same effect but on a different surface. If the condensation has only arisen since you got a stove, are you keeping logs in the property? They could be adding moisture in the air as water evaporates from the wood.
Increasing ventilation is the quickest and easiest solution to this problem.
Condensation inside the stove
This usually happens if a stove is not working hard enough. If flue gases cool before they’ve exited the flue when leaving the stove, this can create condensation, which seeps back into the stove. If that condensation is allowed to sit in your stove, it can cause corrosion and rust.
This is an indication that something about the way your stove is being operated is not correct. It can also lead to…
Tar condensation
If you find tar condensation in your stove, you can bet there is plenty in your flue, too. Except some of it will have solidified into tar and creosote, which further reduces your stove’s efficiency and increases the risk of chimney fires.
Minimise condensation in your stove by:
- burning seasoned wood
- ensuring there is a strong draw up your chimney
- operating your stove at full capacity
- ensuring there is plenty of ventilation in your room
- allowing ventilation into your stove system when it is out of use
Operating your woodburner efficiently reduces the chance of condensation forming in your appliance.
We are getting condensation in the chimney leaking onto the top of the stove when it is burning. This is a new stove in a new building. The drips are black and sticky.
Hi Dave,
This is tar/creosote so, first things first, you need to burn only seasoned logs. Read more here: https://www.gr8fires.co.uk/articles/stoves-use-properly-dried-wood/?utm_source=Social&utm_medium=Social
As for the fact that it is leaking down, is your chimney fully lined? And is there a register plate fitted? If so, you’ll need to get your installer back out to see if there’s a leak/broken seal somewhere in the system.
If you’ve just got a short length of flue pipe running into a full chimney, it might be worth fitting a flue liner if the problem continues when you’re using seasoned wood.
You could also line with vermiculite (https://blog.gr8fires.co.uk/2014/02/26/how-to-use-vermiculite-to-improve-wood-burning-stove-efficiency/) to help the gases reach the top of the chimney before they condense.
Thanks,
Gr8Fires
Hi Gr8fires,
We have had a new stove fitted and used it twice to test it out. We then covered it up whilst we had the room replastered and decorated. Two weeks later I have discovered 700ml of water in the bottom of the stove and rust all around it. Is this from condensation or something else?
We haven’t been living in the house and there has been no central heating fitted yet.
Any thoughts you have would be much appreciated.
Thanks.
Hi Oliver
Hard to know without having seen it or knowing the property. With all the moisture from the plaster drying, no heating in the room and presumably not much ventilation if you’re not living there, it might just have been condensation, though that is a lot of moisture.
Thanks,
Gr8Fires
I’m having terrible problems with condensation in the flue, I use seasoned wood and eco fire pellets, could they be the problem?
Hi Allyson
If the problem’s in the flue, that would suggest the gases are cooling before they have reached the top.
Try operating the stove more powerfully (i.e. a more intense burn) to see if that solves the problem.
Thanks,
Gr8Fires
I have a new stove about three months , it is smoking all the time just took it apart and there is tar all over the inside of it and I think the chimney is the same; the chimney was cleaned but this tar is all over inside the stove, is there any way to get it off the stove , thank you Ann
Hi Ann
Just a wet, soapy cloth on a cold stove is best. If anything is burned on, you could remove it with wire wool and then redo the paint.
If the stove has generated that much tar in such a short space of time, you must be burning very wet wood or allowing far too much oxygen into the stove when it is in use (i.e. the door is open or the vents are open too wide). If not, you could get your installer back to check for any problems.
Thanks,
Gr8Fires
Hi
I have an inset stove and generally burn anthracite. I run the fire hot all of the time 400 – 500deg F)apart from when it is naturally cooling down and it is used about 3 – 4 times a week. The chimney is lined with a S/S liner with a top cowl and the liner is sealed around the top of the chimney pot with cement and there is vermiculite up to the top of the insert (manufacturers requirements), this flue pipe is very clean, no soot just surface dust! I noticed yesterday whilst cleaning that there was some damp patches on the cast iron interior above the door (where the secondary vent plate is and a bit down each side panel towards the front of the fire. Can’t see where this may be coming from and how its getting into the fire? any ideas? first time I have noticed this in the 2 years since I had the fire installed
Hi Paul
It could just be moisture from the air condensing on the metal. You could try increasing the ventilation in the room.
Thanks,
Gr8Fires
Also, to add to my comments above, how do I work out the flue pipe temperature with such an inset stove as there is no pipe visible? Currently I put my thermometer on the top ledge of the stove where the convection vents are (just about enough there) and use that reading but the flue pipe will heat up a lot quicker than the stove front so I don’t know how hot the pipe is getting before the front of the stove heats up.
We have recently moved and replaced a new log burner due to my wife having a lung condition with an electric look alike.The old log burner was fully certificated, had a stainless steel flue with vermiculite surround which is still in situ. Prior to replacing the old log burner (which we never used) we had noticed it had rusty coloured water in the bottom tray which appeared to cum and go, presumably condensation. The installers of the new electric stove seal plated the underside where the old flue pipe had gone and installed an elephants foot on top of the chimney to prevent water coming down the flue. Sadly we appear to get condensation coming through the sealed plate and dripping onto our new stove which only happened last winter. When it rains really heavily no water enters or drips so I am happy it is not rain water and I have had the brick chimney which is on an external wall checked for cracks etc. The chimney is the externally attached type with 3 faces exposed to the elements.The installers of our electric stove can find no reason for the leaking water other than confirming they believe it is condensation coming down the stainless flue even though it insulated! My question is would it be effective to push insulation up the flue for at least the height of where the chimney leaves the internal single storey and then goes on to the outside wall?. I was considering using rock wool pulling the stove to one and pushing it up the flue with drain rods. The quantity of water is not that great when it does cum i.e. 30mm in a 100 x100mm pot. I would welcome your views/comments. The original log burner was brand new having only been used a couple of times and when we moved into the house we had the flue cleaned for a certificate and the cleaner said it was still all clean and had hardly been used.