I've been shopping to get a stainless liner installed in my 7X11" clay tiles flu. It seem most agree that if you run a steel liner into the flu, it should be insulated with a wrap or a poured insulation. My question is why? I mean, If I burn in a flu with clay liner with no liner pipe for years, why would adding a stainless pipe to the flu require the insulation? Isn't the tile insulation enough and adding the stainless liner in addition just even more protection? Just trying to think this through as I digest a few different quotes where everyone seems to spec the job differently.
Why an insulated liner?
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bobdog2o02
Minister of Fire
The insulation will keep in the heat and help induce more draft. I've heard of tons of people with not enough draft, whether from a short chimney or needing insulated. But its few and far between that there are issues with too much draft.
That makes sense. I see you can buy a 1/4" insulated wrap from M-Flex so I would think a 6" liner wrapped with 1/4" insulation would fit in a 7X11 flu. I guess for the added expense, it's worth it.
Insulation should be considered mandatory for a clay liner that is cracked/damaged, and highly recommended for an exterior chimney that will always be cold from top to bottom. But for an interior or center chimney, that is mostly WITHIN the house except for the top few feet, I don't really think insulation is needed. That's not to say it won't help improve draft or reduce creosote, but just that it's much less of a big deal with an interior chimney. Personally, I think a block-off plate in such cases is probably more important and helpful than insulation. (Another option that many take is to simply insulate the top few feet above the roof line.)
Insulation keeps liner warmer, giving better draft, which can equate to less creosote build up. Of course wood moisture content can also add to more build up if the content is high.
Sluggish draft, along with cooler gases can potentially cause more creo buildup. It is also an added safety measure.
Sluggish draft, along with cooler gases can potentially cause more creo buildup. It is also an added safety measure.
Lockpicker
Member
I agree with this. I have an interior masonry chimney with three flues. Two of them have wood stoves with uninsulated liners. According to codes posted daily on here I need an insulated liner because the house framing is against the masonry. Way overkill. My masonry at its least thick point (attic) never gets more than very slightly warm with two stoves going all day.
We can debate weather the code is right or not but the fact is that it is the code and unless you have those clearances insulation is required. And regardless for the small added cost there is a huge benefit in performance. Here is the code btw
http://www.rumford.com/code/clearances.html
http://www.rumford.com/code/clearances.html
I'm liner shopping and the local outfits don't seem to know what liner insulation is- both want to install liner only down my chimney with 13x13" clay tiles. Both say it will meet code requirements. I have an outside chimney so I think there would be a real benefit with the insulation so looks like I might have to do it myself to get the liner install I want...
So, in an exterior chimney...lined with clay liner that are in pretty good shape, can I leave the clay and use a 6" stainless pipe wrapped with 1/4" insulation? My chimney as it is now drafts well, and I don't get much creosote build up at all. I just found a few small cracks directly across from the thimble / where the stove connects and I want to act now and make it safe. Truthfully, I've been wanting to do this for a few years now. Anything to help sleep at night is worth it to me.
Lockpicker
Member
Very well could meet code in you area. There is a huge misconception that NFPA written code Is the final word on on all fire safety everywhere. In reality its up to each locality to adopt these codes or not. I deal with NFPA codes on daily basis.
That said , personally I would insulate just about any exterior chimney stainless liner. Interior masonry chimneys are a different animal and insulation should be looked at on case by case basis.
I just had another estimate provided...by a company I feel good about. They said no insulation is against code, and would not perform well. For my chimney, they said they'll remove the clay liner and install a 6" Stainless/ titanium pipe with a full 1" of wrapped insulation. Lifetime, transferable warranty, ect. Their quote is a bit high, but they're the only ones quoting what I'd like done and I felt good about our meeting, what they had to say, etc. I'm going to sleep on their quote but will probably except their quote in the am.
As someone with a 13x13 exterior chimney who just installed an insulated liner, I can say it works pretty darned well and my stove drafts something fierce (in shoulder season weather even). Never had a liner in there without insulation so I couldn't compare. I only know how it runs with a 6" flue going into the 13x13... hot "clean" burns only ever seemed to happen during really cold nights.
Would do it all over again if I had to. Interior masonry chimney is where I might have a dilemma.
Would do it all over again if I had to. Interior masonry chimney is where I might have a dilemma.
Wonder if you could do 1/4" and not have to remove the clay tile... might be worth asking them.
I have an exterior 25 ft chimney and tried a year without insulation, I would get smoke billowing out of the stove on reloads. Pulled the liner and installed half inch insulation and reinstalled it, sucks like a vacuum now with no spillage, one of the reasons I always recommend just going with the insulation, it beats having to do all that work twice.
Like i have told you before you are correct about nfpa but that code is not nfpa it is from irc and to my knowledge that section is code everywhere in the US. I could be wrong on that if so some one correct me but i know for a fact that it is code in PA where you are from. And besides that if you read the instructions on most liners you will find that insulation is required in order to keep the ul listing when used for solid fuels. And regardless of code they just work allot better with insulation.
1/4" is generally not enough to meet the zero clearance requirement i can say it wont ever but i have yet to see a liner that it did. And even with only 1/4" wrap i doubt it would fit
brenndatomu
Minister of Fire
Those big ole chimneys of yesteryear worked well with those old smoke dragon/wood gobblers. Didn't take much draft to make 'em work. Always plenty of heat wasted up the flue to keep it warm/drafting. Modern burners aren't so "easy breathing" takes more draft to make 'em work right, and with the higher efficiencys obtained that means less heat up the stack so you can't afford to lose any heat to keeping the chimney liner warm. Insulation helps keep chimney cleaner too. I say insulate as thick as you can.
I think this was my size flu as well, and I had to go down to 5.5" liner just to fit the liner (no insulation). It's hard to say but I've never been thrilled with the output of the stove, just not sure if its the stove or the draft. It runs ok, but on most loads I have to have the air setting half way open to cruise, where as my Jotul I back the air down to min and the thing will still roar (taller duravent chimney on that one). But might just be the way they run.
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