Insulated chimney liner controversy?

[bonedoc]

The debate continues...

Just had a long talk with my stove installer who seems to be a pretty smart and experienced guy. He told me he is actually a "master hearth installer" and actually is an instructor for the NFI.(I think National Fireplace Institute?)

Anyway, he claims that in my outside masonry chimney it actually BETTER to NOT put an insulated block-off plate at the back of the stove but rather it is better to put an un-insulated metal plate at the top of the chimney to allow the warm air from the house to warm the air around the 6 " stainless steel tube.

He did say there may be some benefit to insulating the pipe to "allow for easier starting" but that this would not affect the efficiency of the stove.

He seemed to know what he was talking about, but what he said seems to run counter to just about everything I've read on this forum.

Thoughts??

 

[stoveguy13]

tell him to read his code book and follow manf. specs. he is trying to make himself less work his theroy is not holding much value with me insulate the liner and put in a block off plate at the bottom it is the right way to do it ask him if he will come back for free if you are not happy with his install. and bring it up to spec my guess is no.

 

[stejus]

My liner is not insulated yet. My sweep was against a block off plate because he felt the heat in the chimney flue would keep the liner warm, thus less creosote. I am capped at the top of the chimney with a stainless steel plate sealed with some sort of glue or something.

I ran the stove this way for about a week and noticed I was not getting much warmth from the stove. It was an extremely cold week. I decided to put some insulation in the damper area that was wide open. I used R30 unfaced Fiberglass. There was an immediate change in the amount of heat output.

The drawback to this is now I have a better chance to create creosote. I run the stove wide open every morning with three large splits to burn off any creosote that may be there from the day before.

This spring I am having the liner insulated and be doen with it!

 

[oconnor]

Chimney liner can hit 1000*- 1200F in normal operation - it doesn't need warm air from the stove to heat it up, it needs insulating to keep from losing its heat to the surrounding cold masonry. You can check out the NFI Best practices for liner installs link in my signature block - maybe the NFI Master Installer would like to see it too.

 

[bonedoc]

Chimney liner can hit 1000*- 1200F in normal operation - it doesn't need warm air from the stove to heat it up, it needs insulating to keep from losing its heat to the surrounding cold masonry. You can check out the NFI Best practices for liner installs link in my signature block - maybe the NFI Master Installer would like to see it too.

I believe his point was that the warm air around the chimney liner would help facilitate draft.

Why is it better to insulate around a block-off plate at the bottom of the chimney? He said that doing this would make the air around the chimney liner on an exterior chimney frigid and make draft difficult.

Still a bit confused....

 

[begreen]

It will be frigid, for about 5 minutes. After that it will be radiating heat pretty intensely as long as you have a good robust starter fire. The block off plate will help keep the stove hotter. Ideally, the liner would be insulated as well. Then the concern about liner frigidity is a non-issue.

 

[bonedoc]

So....to review.

I should INSIST on a block off-plate at the bottom of the chimney(not at the top as intended by the NFI certified installer) AND insist on insulating the chimney liner.

I can' t figure out why they thought I was crazy for wanting this. The stove shop is a very busy one that installs LOTS of stoves in CT. They have been mentioned several times before by other posters with very positive reviews.

Could there be just different schools of thought?

 

[Shari]

So....to review.

I should INSIST on a block off-plate at the bottom of the chimney(not at the top as intended by the NFI certified installer) AND insist on insulating the chimney liner.

....ummmm.... add a chimney top plate to your list.

Shari

 

[begreen]

My guess is because it's more work and it will cost more. Stove shops try to stay competitive and understand that for many people an expensive flue installation is a bit of a shock. However, if you look at any well-made house from the 1700 or 1800s, one thing they have in common is that the original chimney was inside, preferable in the center of the house. Exterior chimneys didn't come into vogue until central heating with wood was no longer the goal.

What you are trying to do is to compensate for the exterior chimney. Anything you can do to keep the flue pipe hot and prevent the stove from losing heat to the exterior mass of the chimney will be beneficial. Letting the stove keep the pipe hot by leaving out the block-off plate is a very common practice. But an insulated liner is better and safer.

 

[karri0n]

BG,

any insight into why the exterior chimneys are used? Is this for looks, cost, space, all of the above?

 

[oconnor]

Chimney liner can hit 1000*- 1200F in normal operation - it doesn't need warm air from the stove to heat it up, it needs insulating to keep from losing its heat to the surrounding cold masonry. You can check out the NFI Best practices for liner installs link in my signature block - maybe the NFI Master Installer would like to see it too.

I believe his point was that the warm air around the chimney liner would help facilitate draft.

Why is it better to insulate around a block-off plate at the bottom of the chimney? He said that doing this would make the air around the chimney liner on an exterior chimney frigid and make draft difficult.

Still a bit confused....

The air around the chimney isn't going to keep it warm - keeping air away with insulation will keep it warm. The liner will radiate heat to the surrounding brick, and any air change will cool the flue, so the first way to keep the flue liner hot is to reduce the radiant heat - insulation around the liner does that. The block off plate keeps air from rising up and out the inevitable gaps and cracks in the brick structure - the plate helps keep the heat in the house by helping stop hot air leaving, and in doing so it helps stop drawing any cold air from outside into the house.

I see no great value in insulating above the block off plate - it seems to me that the air temp around the flue and behind the plate will get higher than the air temp under the plate inside the house given the small air volume and flue liner temp. That said, use an insulation rated for 2000F / 2100F (US / Canada ratings for your liner) and you won't do any harm.

If you can't get a tight fit around the liner with a block off plate, the insulation may help with the air seal - that would be where I see the insulation above the plate being a benefit.

 

[jtp10181]

Just FYI we don't install a lower block off plate on any installs we do. Only have once that I know of per customer request (he was snooping around on here). Never had any problems. The kits we use comes with a top plate and we seal that down with silicone.

We also used to not even offer insulation on the liners, until I found out why it was needed. No we do it on every install because you never know if the entire chimney structure was built correctly and is safe to use without the insulation.

 

[LeonMSPT]

Following the "chimney fire" thread...

Individual had a fire between the liner and the original flu. Apparently, there was some old creosote hanging around in there. Temperatures got high enough inside the liner, and conducted to the outside of the liner, igniting the creosote outside of the liner.

My cousin, who runs a shop and has been installing and servicing the things for quite awhile, recommends a "zero clearance" double insulated liner often to people relining and old chimney that may be impossible to thoroughly clean. That fire between the liner and the old flu would never have happened had the install been done that way. Cost? Seem cheap once he gets done with what he has to do now...

The debate continues...

Just had a long talk with my stove installer who seems to be a pretty smart and experienced guy. He told me he is actually a "master hearth installer" and actually is an instructor for the NFI.(I think National Fireplace Institute?)

Anyway, he claims that in my outside masonry chimney it actually BETTER to NOT put an insulated block-off plate at the back of the stove but rather it is better to put an un-insulated metal plate at the top of the chimney to allow the warm air from the house to warm the air around the 6 " stainless steel tube.

He did say there may be some benefit to insulating the pipe to "allow for easier starting" but that this would not affect the efficiency of the stove.

He seemed to know what he was talking about, but what he said seems to run counter to just about everything I've read on this forum.

Thoughts??

 

[bjkjoseph]

my hampton manual states you do not need a block off plate,if the liner goes all the way up,to the top of the chimney and i see the logic in that.but not insulating the liner in an outside chimney in a cold climate is a big mistake,you are going to have to clean the chimney quite often.instead of the block off plate you can just use insulation.now for your installer doc,that was a good one he's an instructor at the national fireplace institute i got a good laugh at that one,and before that job i bet he was an engineer or an ex navy seal any bull chit artist worth his salt is an ex navy seal,do your self a favor find a new installer.

 

[slayer7]

It's interesting...I'm from the same area as you and have also had many "experts" come out to quote a chimney liner installation for a woodstove insert. Most claim there is absolutely no reason for insulating the liner if your chimney is "up to code" which they say it is after a cursory inspection. These installers say they are CSIA certified and/or members of the National Chimney Sweep Guild and state that they never insulate a liner or install a blockoff plate, have been doing this for 10,20,etc years and their installs are just fine. Their reasoning is the clay liner tiles in a chimney that is not damaged provide enough heat retention that the insulation is not necessary. Most did not mention a blockoff plate, didn't know what it was or offered to jam some insulation around the damper if I thought it was necessary. One installer that had been "doing this forever" wanted to jam a liner down the chimney that was comprised of multiple sections cobbled together with some type of connectors and screws (hmmm...won't this affect draft, cause fumes to leak out or creosote to drip from the seams?? nah...that's ridiculous, we do this all the time . :roll: ) There was only one installer who came out and right off the bat said he's more expensive because he insulates the entire liner and customizes a blockoff plate on the bottom and that's the only way he would do the install. So, I guess there's a lot of "professional" installs that have none of these features. As I don't have evidence one way or the other personally, I can only read the experiences of others here who swear that those measures greatly improve your stove's operation. I'm wondering why there is such a disconnect between the installer world and what others say here...maybe as someone mentioned above they are trying to keep the price tag down since it's already an expensive job or making the job easier for them. Personally, both items logically make sense as to how they would affect the stove's operation and would be safer. I guess the old adages "buyer beware" and "you get what you pay for" apply here as well.

 

[burntime]

Not an expert but I have had my setup both ways. With insulated liner and without. With block off plate and without. I can say with 100% certainty that you are not utilizing the max efficency if you do not do it. Its like driving a car in the 2nd highest gear on the freeway and not taking advantage of overdrive. Liner insulation also makes sure your chimney is safe. What is your life worth? If very little then don't do it. My guess is a lot more than chimney liner insulation. The block off plate also retains much more heat. This bs about not drafting well with a plate is mall ninja talk. I have about 12 - 13 ft above my stove and can lite mine in 48 degree weather. I know this because it was damp and wanted to dry the house out. If you do not insulate the liner and install the blockoff plate you are not doing the customer a service. I asked the questions and was lied to by a stove shop and hampton, only to get a 180 degree turn when asked a year later when I had issues. Do it right the first time and sleep warm and safe at night.

 

[mellow]

As I stated to the OP in the other topic he started, installers are lazy and look for the cheapest fastest way to get you installed (Not applicable to every installer). They work the minimums code wise to make the most profit. Also think about it this way, you pay them now to install a liner with no insulation, mid-way though the winter you have draft issues, they NOW would like to take the liner out and insulate to help you, or pour down vermiculite for a set $$$. Which way would you think is more profitable for them?

As has been stated already this is on a per installer basis, some do it right, others do the bare minimum and it works most of the time.

So if the OP would just follow my advise I gave him before and insulate his liner and put in a block off plate NOW, all will be fine in chimney land. After all this "research" you could probably just do it yourself now, I find a cooler full of beer will get you helpers.

 

[burntime]

In Wisconsin the charge is Lienies and venison jerky! Good luck, I redid min and it was pretty fast. The spray glue used on the liner is like being tarred and feathered. Wear gloves

 

[mellow]

Speaking of advise, Do not put the Insulation tape pieces on your lip while you fold the insulation over the liner, a good chunk of my lip went with the tape.

 

[Northeaster1]

I never ran my new PE Pacific insert without a block-off plate, as I made one myself, after having a certified sweep install the solid un-insulated liner, with a short piece of flex to the stove.

The approx 18' liner is un-insulated, and is in an outside, cinder block chimney, which has 12x12 clay and was very clean.

Re: the issue of cresosote - I swept my liner after about 2 months of regular, but not always 24/7 burning, with good wood, and found very little creosote - mostly at the top, as the top 4" that stick out above the outside chimney are not insulated either, and cools off much faster. Creoste was very dry / flaky.

I have no problems with draft, even at startup, and have never smoked out the house, etc.

We have been extremely satisfied with the heat output, draft, etc. We are in a fairly cold climate - Easter Canada, and it has worked great, without an insulated liner.

Would it work better with one - maybe, but I have lots of draft, and very little creosote, so I am not running out and insulating it anytime soon. If I suffered form low draft, or lots of creosote buildup, yes, I would!!

 

[LeonMSPT]

It's very much buyer beware. Few universal standards, other than NFPA 211, and that's precious little, little known, and toothless as far as enforcement in most jurisdictions here in Maine at least.

There is a very wide variety of things that will "work". There's even a wide variety of things that are "safe". It's a wide spectrum in reality. My goal, for my own projects be them for myself or loved ones, isn't just "to work" or "be safe". I want it to work as well as it practically can for the money, and be safe under the rarest of extreme conditions.

Rule with fire is, plan for the worst case... it'll never happen. Fail that, bet your bottom dollar it will.

 

[jtp10181]

I want it to work as well as it practically can for the money, and be safe under the rarest of extreme conditions.

That is very well said. That is how we look at doing installs for customers.

 

[NFreiermuth]

O.K.
I'll chime in.

I am a proponent of insulated chimney liners. The insulation eliminates ANY and ALL confusion about codes and eliminates the need for the fire department should the old flue not be thoroughly cleaned. Yes, that liner will get hot enough to ignite any remaining creosote. I do not have a bottom block off plate because the room just wasn't there to get it in. The bottom IS packed full of the same ceramic wool (KAO Wool) by Fiberfrax, I used to insulate the liner. The Hampton uses the 5.5 Inch liner and I wrapped this with 1 Inch of the ceramic wool. The tricky part was getting the liner to lay straight enough to wrap it length wise with one continuous piece of insulation. I did not use any type of glue, but rather wrapped the liner and the insulation with stainless chicken wire fence. I then tied it up tight with stainless steel wire. I figured if the worst happens, at least the insulation stays intact and in-place. Exactly what is needed in a hairy situation. The top is capped with a stainless steel plate properly fitted to the flue and high temp siliconed in place. The rain cap is a propper topper from our founder craig. Once off the roof, it looks like and old fashioned chimney topper, not a flex liner.

I pulled a permit to install my new stove. Both the town Fire Marshall and Building Inspector stopped by. I told them straight out that I couldn't get a bottom block off plate in place, but I wanted them to look up the flue before I stuffed the gap so they could see the wrapped liner. The Fire Marshall said "Excellent Job" and he wished that others would take such pride and care to install a flue properly. The buildng inspector said there were no strict rules about the liner or insulating it. He was mainly concerned about illegal flue tapping. He asked if he could take a few pictures to show other folks when they have questions for him. He took his pic's and left. A few weeks later, I was sent a nice letter to give to my insurance company stating the attention paid to "Above and Beyond" what is legally required by law for a solid fuel burning appliance.

The draft on the stove has always been excellent. Smoke NEVER gets into the house and starting the stove cold couldn't be easier. A few fat wood sticks , some small splits, and it's in secondary burn in no time.

The best part is the stainless steel chicken fence was $25 and the roll of Insulation was $105. So fo $130, I met the NFPA standards AND can sleep peacefully at night.

My old Hearthstone II was in another home years ago, but since we burned coal in it, I installed the 6 Inch Class A Security Chimney. It was a pre-EPA smoke dragon on wood, but a whole nother' story with coal. After that install, I couldn't see the reason to NOT insulate a chimney liner for the Hampton install.

 

[burntime]

Shop dog, you did well, I was going to do the same thing but the bottom line is if it has no listing you may have accomplished it, but it did not get the nod if you know what I mean. I ended up buying the kit which is the same but with a foil outer face. I think they are like 300 bucks. Its like taking the cord off your toaster, you lose the ul listing when you splice one on. Same with non-kits. I don't remember the exact terminology, basically you achieved the same thing for a little less money but it is not a 1 for 1. I know what you mean about the great draft though, mine is hotter, cleaner, and burns longer with a liner. Now if I could only train the Labrador to fill the stove when I am gone ;~)

 

[bonedoc]

Glad to have inspired such vigorous discussion.

I have installed my FPX elite 33 insert with a rigid 6" fully insulated liner in my 30' exterior chimney.(Installer said it was the hardest and most dangerous install he has ever done....)

Block-off plate sealed at the top; nothing at the bottom...(still not sure if this will help)

So far it seems to start and draft pretty well. I have bone-dry oak and maple so I suppose the real test will be when I'm trying to run it with damp wood.

Would like more heat but am still playing with the air controls.

Thanks again for all the A-D-V-I-C-E fireplace gurus...