Advice on smoke chamber seal and liner insulation

[kitand]

Just got a Vogelzang Colonial delivered. I'm DIYing the install and am wanting to order the liner now. I've read a fair amount on this site and others about liners and installation, including of course sometimes conflicting information (I can live with that: part of a democracy, I guess!). Three questions:

1. Best removable way to seal smoke chamber?
The instructions for the insert indicate that I should "seal smoke chamber" but that "accomodations for inspection and cleaning should be maintained," which I assume means the seal should be removable. Now, I'll be sawing a gap in the cast-iron damper frame that is there near the smoke shelf to make enough room for a 6" liner (I removed the damper flap so there's an open slot there already, but just maybe 4" wide or less). I've seen pics on hearth.com and elsewhere of people fabricating steel sheets as a smoke seal and "flue gooing" them in place around the liner, apparently with some sort of insulation on top of them. But this seems rather permanent. Is there some removable way to go about this, and perhaps an easier way, too? Call me a dreamer, but is there some sort of rigid insulation material that would work just by itself, and be fastened there so that it could be removed easily? I will also be getting it inspected by my city, so I suppose it might be good to do something that looks a bit "standard."

2. Would liner insulation really help?
My brick chimney is in the middle of my house. My house is one story, with an unfinished attic. It goes up through the attic at about the top ridge of the roof and extends about 3 feet. It's built together with the chimney for a second smaller fireplace in another room (the flues are totally separate, and the other fireplace will remain as is). The liner will be 15' long. I've read in some accounts that liner insulation is not necessary in chimneys that are not on an outside wall. Furthermore, I'm in Seattle area, where it's not generally very cold. How helpful would liner insulation be in my situation?

3. Any reason to put an inline damper in the liner? I see they're sold. Haven't read about any other owners of this model doing that.

 

[Squisher]

Bear in mind that while insulation becomes less important for performance on an interior masonry chimney, conversely it becomes more important for safety. The determination for whether you would require insulation or not should be made by determining if the existing interior chimney has a verifiable 2"s of clearance to combustibles. If it doesn't or you can't verify it. Best insulate for safety.

 

[bholler]

1. Best removable way to seal smoke chamber?

If you are doing a full liner to the top there will never be any need to remove any of it for cleaning. Make sure the old liner and smoke chamber are cleaned very well first though.

As far as the insulation goes squisher pretty much covered it there here is a link to the applicable code for the required clearances.
http://www.rumford.com/code/clearances.html

 

[Easy Livin’ 3000]

Unless you have clearance issues inside the chimney, apply the insulation to the liner. I think it'll cost you about $200 at most, and then you can burn away with little concern about whether your interior chimney is seperated from the framing in your house.

I think the wizards here still owe you their insights about how to do your block off plate. I'm eager to find out for myself.

 

[Corey]

...

2. Would liner insulation really help?
My brick chimney is in the middle of my house. My house is one story, with an unfinished attic. It goes up through the attic at about the top ridge of the roof and extends about 3 feet. It's built together with the chimney for a second smaller fireplace in another room (the flues are totally separate, and the other fireplace will remain as is). The liner will be 15' long. I've read in some accounts that liner insulation is not necessary in chimneys that are not on an outside wall. Furthermore, I'm in Seattle area, where it's not generally very cold. How helpful would liner insulation be in my situation?

Actually, a only 15' liner (which will not create a lot of draft) plus 'not very cold' (which doesn't generate a lot of draft) plus likely humid/wet/rainy Seattle air (which is lighter than dry air and reduces draft) are three reasons I WOULD insulate the liner.

Stove efficiency is another key reason. If you aren't recovering 'useable' heat from the flue (say an exposed pipe right in the living space) then that heat is essentially 'lost' and adding insulation will minimize the loss. This is less important with your central chimney, where the heat may eventually make it into your house - though it may be very low grade heat and many hours after the stove is fired. Though the losses can be considerable with an outside wall flue... or even an inside flue if buy wood at market rates.

 

[double-d]

The inline damper is not needed and I'm not sure how you would access it even if you installed one

Damper Block off plates are used to seal off your damper area when inserting a stainless steel liner kit. It will help prevent the hot air, created by the insert or stove to rise up into the chimney up into the chimney chamber, which reduces the amount of heat that is intended for heating.

Using approved blanket insulation sections can be placed to help insulate it. Using the blanket insulation could be used by itself...if all else fails.

 

[mstoelton]

Instructions for creating a block-off plate can be found on this website. Search for "making a block-off plate".

 

[kitand]

Thanks all. BTW I have seen already the hearth.com page for making a block-off plate. It has great tips, but it seems more permanent than what my insert instructions seem to ask for, which is why I posted this.

Squisher, the chimney combustibles clearance is 2+" where my chimney passes thru ceiling, but less than 1" in easily visible places as it passes thru roof. Funny that I never considered this to be a problem. Have never noticed the bricks/blocks ever getting hot before, but have not burned fires for extended times in the fireplace, and I suppose inserts make the chimney hotter due to chimney being sealed on top and bottom.

Corey, good points, except I don't understand the rationale for insulated liners and stove efficiency. Seems like the insulation would force more heat up and out the chimney resulting in loss of heat. Without insulation, I'd expect the chimney to get warmer and help heat the house more. Of course, that point is moot if fire protection is the main concern.

 

[yooper08]

To answer your first question, install the block off plate after the inspection. You can have all the parts ready to go, just don't seal anything up (including at the top for the chimney cap) as the inspector will probably want to look inside there as well.

As for the insulated liner and clearances, during a normal burn the bricks may not get that hot. The main point is really in case there's a chimney fire and keeping combustibles safer from catching fire in that situation. The point is and not to beat a dead horse, if you don't have the clearances, insulate it for safety sake.

As for performance/efficiency with an insulated liner, your stove efficiency won't really go down. The heat we're talking about at this point is going to go up the flue anyway, you're just not absorbing as much of it in the masonry. This may be semantics here though as I know what you're getting at. But again, safety over performance in this case.

 

[begreen]

Seems to be a documentation error. It looks like whoever made up the installation instructions copy and pasted the info for a direct connect installation image without removing the "seal the smoke chamber instructions" for the full liner install. With a full liner the smoke shelf area should not need inspection or re-cleaning unless the liner fails.
A block-off plate is not required for a full liner. That said, if this is an exterior wall chimney there is a benefit to installing an insulated block-off plate. It will keep more heat around the insert's convection jacket thus helping raise the heat output.

 

[weatherguy]

It's interior BG, I affixed my block off plate with magnets.

 

[Corey]

...
Corey, good points, except I don't understand the rationale for insulated liners and stove efficiency. Seems like the insulation would force more heat up and out the chimney resulting in loss of heat. Without insulation, I'd expect the chimney to get warmer and help heat the house more. Of course, that point is moot if fire protection is the main concern.

Well... sort of.

At the end of the day, the 'smoke' needs to reach the top of your flue with some given temperature to create enough draft for the stove to continue working. Any heat lost through the liner is essentially heat lost from the smoke. Essentially, any heat lost from the smoke along the journey up the pipe means more heat you have to put in initially at the stove.

If the heat lost along the flue pipe is directly recoverable and usable to the room, (say a flue pipe exposed in the room) then fine... no harm, no foul. If the heat is lost to your interior chimney, then some of it may be 'recoverable' and that is also fine. But say you fire the stove at night for a quick burst of heat. The heat lost in the flue may slowly warm the masonry. Then that masonry keeps your house slightly warmer over the next day while you're out at work.

It might be arguable if the heat which went into the masonry was really 'usable' if it was low grade heat and kept the house warm while you were away... which you may not care about anyway.

Overall, the insulation means you get heat exactly where you want it ... from the stove - and a minimal amount goes to 'wasted' or secondary type heat which may or may not be needed by the time it finally enters the room.

 

[kitand]

weatherguy, great tip! Magnets might work well given cast-iron damper frame as well as lintel. Why didn't I think of that?

begreen, I think you are quite right. I just checked 2 manuals of similar models at other companies, and neither requires a smoke chamber seal for a full liner, only for a direct connection. The manual for my model ONLY allows full liner (specifically says no direct connection), but also calls for the smoke chamber seal (aka damper block off). The more I think about it, this just doesn't make sense with physics. If I sealed my chimney both on top and at the damper, then when air is heated in the chimney it will pressurize and want to go somewhere. It would probably break the seals somewhere pretty soon.

Per my local inspections dept, I'm supposed to "follow the manual" but in light of your tip, I suppose the inspectors will be very accustomed to NOT seeing a damper block-off and will probably not mind. However, insurance might mind if there were ever a problem. I think I'll email the manufacturer about this and see if they might issue a "correction" to me.

 

[bholler]

It would probably break the seals somewhere pretty soon.

no we seal top and bottom on every fireplace install and have never had an issue first off I doubt you will ever get it sealed well enough to build pressue regardless but even if you did the pressure would not be enough to damage anything anyway. But a good fitting block off plate with insulation stuffed above will be tight enough to serve the purpose anyway.

Btw I seriously doubt the inspector will even look at the plate.

 

[kitand]

Followup:
Begreen, I contacted manufacturer to ask for a "correction" in the manual, but they replied saying that,

"This [sealing off smoke chamber with damper block-off] is a requirement per the NFPA211 standards for solid fuel-burning appliances. So, that would have to be sealed off to be up to code."

If that's true, it does seem odd that most other manufacturers don't indicate this in their manuals for a full-liner install..

Unfortunately, I can't google the code directly (it's offered for sale), but did come across this interesting 2006 hearth.com discussion related to that code and the damper block-off issue.
https://www.hearth.com/talk/threads/international-residential-code-concerning-damper-block-off.2671/

Bottom line, since the manufacturer won't give a correction, I'll probably just snip me some steel and seal with magnets as weatherguy suggested.

Thanks all.

 

[bholler]

If that's true, it does seem odd that most other manufacturers don't indicate this in their manuals for a full-liner install..

It is not true for a full liner at all.

 

[begreen]

Followup:
Begreen, I contacted manufacturer to ask for a "correction" in the manual, but they replied saying that,

"This [sealing off smoke chamber with damper block-off] is a requirement per the NFPA211 standards for solid fuel-burning appliances. So, that would have to be sealed off to be up to code."

If that's true, it does seem odd that most other manufacturers don't indicate this in their manuals for a full-liner install..

Unfortunately, I can't google the code directly (it's offered for sale), but did come across this interesting 2006 hearth.com discussion related to that code and the damper block-off issue.
https://www.hearth.com/talk/threads/international-residential-code-concerning-damper-block-off.2671/

Bottom line, since the manufacturer won't give a correction, I'll probably just snip me some steel and seal with magnets as weatherguy suggested.

Thanks all.

They are quoting NFPA out of context and incorrectly for a full liner.

 

[kitand]

Begreen, bholler--I emailed manufacturer (US Stove) again citing your latest comments that they were quoting the NFPA out of context. Got this different reply from a different tech there:

"He [the customer] is correct, NFPA 211 is worded for running directly into a masonry flue. We [US Stove], however, recommend the use of the non-combustible sealed smoke chamber as an added safety . We do this to prevent any smoke or cold air intrusion and due to the fact that we do not know the integrity of the masonry chimney that it is in."

 

[begreen]

Nonsense. With a full, insulated liner the integrity of the chimney is secondary assuming it's not going to fall down or leak water. There is zero smoke or wood gas being transported or seen by the masonry with a full liner.

That said, there is no harm in adding the block-off plate and some added benefit when used in an exterior wall fireplace.

 

[bholler]

"He [the customer] is correct, NFPA 211 is worded for running directly into a masonry flue. We [US Stove], however, recommend the use of the non-combustible sealed smoke chamber as an added safety . We do this to prevent any smoke or cold air intrusion and due to the fact that we do not know the integrity of the masonry chimney that it is in."

"This [sealing off smoke chamber with damper block-off] is a requirement per the NFPA211 standards for solid fuel-burning appliances. So, that would have to be sealed off to be up to code."

I dont understand how both of these statements could be true they seem to be contradicting themselves. A plate is absolutely not required by code if you are running a full liner. But regardless we put block off plates on every stove or insert install into a fireplace. And there is absolutely no reason with a full liner that the plate would ever need to be removed for cleaning.

 

[kitand]

Begreen, bholler--I'm sure you're correct that the company's position doesn't make sense. I've read of the professional installations which involve excavating out the terra cotta liner just to make room for the full stainless liner, and that apparently flies fine.
Anyway, I'll just put in a simple block-off to suit their fancy.
Regards

 

[bholler]

Anyway, I'll just put in a simple block-off to suit their fancy.

We both completely agree that a block off plate is the right thing to do but it is not required by code and it does not have to be easily removable.