Chimney Liner and Creosote

[Hunter17]

Hi. I am hoping to get opinions based on those with more wood burning experience than me. Some background, this is our first winter in a new to us house built in 1980. We have a vented fireplace on the main living floor and an older non-epa wood stove in the basement. In June 2021, we had a local chimney sweep company come out to do an inspection of both flues and to perform cleaning if needed. They ended up cleaning the fireplace flue but said the wood burner did not need cleaned at the time. The prior owners stated that they didn’t use the wood burner during their time in the house (13 years) but had no insight into what the owners before them may have done. Through the summer I read up quite a bit on the effects of burning green wood and have been doing my best to avoid that by burning only standing dead trees that I also moisture tested. We have been having a mild winter and to date I have probably burned 1/3 cord or so. I burn primarily in the evening for 4 or 5 hours before going to bed, so this isn’t a 24/7 thing for me. Anyway, I climbed up on the roof today to see what potential creosote buildup was looking like. When I removed the chimney cap for the wood burner, I was greeted by a glassy layer of creosote running the length of the clay tiles (20+ feet from the bottom of the flue to the cap). This layer was very thin and not particularly tarry to the feel but I was surprised to see it since all I have been getting in the stove itself when cleaning it is soot and ash. Now I’m nervous to burn since I obviously don’t want a chimney fire but I have no idea how my burning technique could have cause such a layer so quickly. Unless of course the chimney sweep just didn’t want to deal with it in the summer heat. I could set up a cleaning again but chimney sweeps are busy in winter and I don’t think they’ll be able to get to me for a month or more. Does anyone have any advice or am I reading too much into it? 1 pic is the inside of the burner and the other are some chunks I pulled off the liner.

 

[begreen]

Low and slow burns in a cold exterior chimney can build up creosote quickly, particularly with many cold startups.

What stove is this with? What is the ID of the chimney flue that the stove is connected to?

 

[Hunter17]

Low and slow burns in a cold exterior chimney can build up creosote quickly, particularly with many cold startups.

What stove is this with? What is the ID of the chimney flue that the stove is connected to?

You’ll have to forgive me since I don’t know much about my setup. I haven’t seen any kind of identification number or name on either the stove or piping into the wall. The main flue looks to be standard rectangular tile though. For all I know the stove was handmade, it would definitely fall into the smoke dragon realm however.

I can see continual cold startups causing creosote issues as you mentioned. And there may have been times I choked down the fire too much in an attempt to get longer burns (been playing with both the air intake openings as well as the pipe damper since the size of this thing allows it to just eat wood like crazy). But I’m still surprised that I would be getting these results after not even a half cord.

 

[stoveliker]

keeping the flue hotter is important to avoid condensation.
Also, how do you test moisture? One needs to test parallel to the grain on a freshly re-split surface (that is preferably at room temperature). Measuring on the outside does not mean much.

 

[Hunter17]

keeping the flue hotter is important to avoid condensation.
Also, how do you test moisture? One needs to test parallel to the grain on a freshly re-split surface (that is preferably at room temperature). Measuring on the outside does not mean much.

Appreciate your response. I do measure moisture on a fresh split. Of course I don’t measure every split that goes in the stacks, but I think I do enough to get a feel for which parts of the tree may be drier and ready to go vs wetter. Starting to think that if this buildup is solely the result of my burning over the last month or so that I must have been trying to squeeze too much burn time out of the wood by being too restrictive with the airflow. That’s the only thing that seems to make sense, besides the sweep just not wanting to deal with it on a summer summer day when they were out here (which I feel would be pretty negligent on their part, so I doubt that is what happened).

 

[stoveliker]

I think you may be right.

For evening fires, maybe try shorter hotter fires (enjoying the heat a bit after the fire dies down). The ambiance is then also shorter, but safety...

Another option (possibly, depending on sizes) is to add an insulated stainless liner in the chimney. It'll keep it warmer, hence less (chance) of condensation.
This does not prevent the need to not produce creosote in the first place though - because blowing it out into the environment is not the best either, even if you can keep your chimney clean.

 

[Hunter17]

I think you may be right.

For evening fires, maybe try shorter hotter fires (enjoying the heat a bit after the fire dies down). The ambiance is then also shorter, but safety...

Another option (possibly, depending on sizes) is to add an insulated stainless liner in the chimney. It'll keep it warmer, hence less (chance) of condensation.
This does not prevent the need to not produce creosote in the first place though - because blowing it out into the environment is not the best either, even if you can keep your chimney clean.

Good points. Modifying the liner is something I’ll have to ask about at my next cleaning. Not sure how much something like that costs, but I imagine they aren’t giving them away haha. Either way, if I can determine if the long term benefit is worth the cost, I’ll be on board.

 

[bholler]

Good points. Modifying the liner is something I’ll have to ask about at my next cleaning. Not sure how much something like that costs, but I imagine they aren’t giving them away haha. Either way, if I can determine if the long term benefit is worth the cost, I’ll be on board.

That is definitely a home made stove or one made at a local shop. It looks like it has 6" pipe on a stove which looks like 8 would be more appropriate. It then goes into a much larger clay liner where the gasses expand causing them to cool rapidly. That ammout of buildup is not at all uncommon for old primitive stoves like that. Especially going into an oversized uninsulated liner

 

[kcmclellan]

Yup, it'll probably cost a few bananas to get yourself properly established to burn cleanly and safely in your home... But for many of us that love to burn wood it's a very worthwhile endeavor. I'll just address this comment as if you're one of the deeply devoted woodburners that make up a big portion of the members of this incredibly informative site. So first off you probably want to think about investing in a new stove. The price range for stoves can be mind boggling, but I got myself a simple looking, large (3 cf) steel stove, a Drolet Austral, for about $1000.00 (txs incl) in the Spring of 2014. I'm still in love with it. In your case, you would also want/need to have your old tile lined chimney professionally cleaned to remove any/all of the creosote that's in there, and then have a proper insulated 6" liner installed, so that you could burn cleanly without worrying about producing buckets of creosote every time you fire up your stove. Mind, you'll probably wind up burning alot more regularly once you have a modern, new & safe set up to work with, and turn into a 24/7 burner shortly thereafter... 😊 And that will be great too, because you'll probably end up saving money once you're less reliant on your old more traditional methods of home heating... The thing is, of course, you'll be wanting to save money, because I forgot to mention that the cleaning & installing of the new liner will probably set you back a few grand, I'mthinking maybe $4000.00 to $5000.00...... My straight up from the basement and through the roof (of a bungalow) install for a 6" chimney cost $3500.00, including hooking up to a new 1.8 cf stove in August of 2013. I sold that for $500.00 when I switched out for the Drolet Austral in March 2014... 😊 And from that moment right up to this moment right now as I speak to you, I have never, ever, had a moment of regret or doubt about the choice I made (with the help of my dear and loving wife, I should add!). And I surely believe that the initial cost of installation etc., has been easily smoothed out & over in electricity costs, not to mention in terms of peace of mind & contentment (for the dogs too). Needless to say, I would surely recommend that you think over the proposition very, very carefully... 😊

 

[MR. GLO]

I see a pipe damper are you using it?
How are you measuring flue temps and stove top temps? I cant see any in photo.

You need a internal flue temp and good wood to burn with that setup.

Most likely burn hot but use damper to elp control flue temps ....but each morning you need to run flue hot. 850 ..or so... plan on one cleaning Jan and one end of season until you get an idea.

 

[fbelec]

i had a clean masonry chimney when i started (the people before me didn't burn the stove for between 5 and 6 years) and three weeks later had a full blown chimney fire that had 5 to 6 foot flames shooting from the chimney. so my point is it doesn't take long to creosote up a chimney. and also so that you don't burn wrong get a stove pipe thermometer and place it 18 inches above your stove and don't burn the stove any less than 300 degrees. best if a little higher like 375 400. and burning slow to hold a fire longer is not a good thing it has to stay high on the thermometer to keep your chimney warmer.

 

[kcmclellan]

i had a clean masonry chimney when i started (the people before me didn't burn the stove for between 5 and 6 years) and three weeks later had a full blown chimney fire that had 5 to 6 foot flames shooting from the chimney. so my point is it doesn't take long to creosote up a chimney. and also so that you don't burn wrong get a stove pipe thermometer and place it 18 inches above your stove and don't burn the stove any less than 300 degrees. best if a little higher like 375 400. and burning slow to hold a fire longer is not a good thing it has to stay high on the thermometer to keep your chimney warmer.

Wow! That must of scared the bejeebers out of you! Do you still burn using the masonry chimney, or did you end up getting a liner installed? I wonder if a lot of people start burning with an existing stove in a new house that is already set up running an existing masonry chimney, and then come to learn later (through scary and/or dangerous situations) that that the masonry chimney is not an ideal set up?

 

[fbelec]

i still use the masonry chimney. the fire was that i was burning to low of a temperature. and also burning what the dealer said was seasoned wood but it was sizzling so i know it is not dry enough. now i know better i don't have chimney fires. i burn hot fires. if i only have to raise up the temp just a few degrees then i limit how much wood goes in the stove but still burn hot. my manual says that the max running temp is 700. and that is ok to go over that on a initial firing but i burn at 625 on the stove top give or take 50 degrees. that leaves my chimney connector pipe between 325 and 400. at about 350 i checked my output at the top of the clay liner with a IR thermometer and it is registering 310. i use a magnet thermometer so i can keep track of stove pipe and stove top temps