Block off Plate install...insulation and creosote

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gparzych

Member
Jan 8, 2012
15
CT
Looking to put in a lintel plate with a pass through for the liner for my hearth mounted stove. I'm confident I can hang it up there by resting it on some removable lag bolts or similar. Any advice on thickness of steel (or other material)? Since the stove is in there already, the pass through would have to be open at the back. I'm looking to deflect some additional heat into the room.
 
Not exactly sure what you are asking? Can you take some photos and possible add a little diagram of what you are attempting to do? I ave done a lot of iron work with lentals holding up brick/block for structural rigidity but have no clue what you are trying to support?
 
Most often, the term "lintel" refers to a horizontal load-bearing structural member set in place to support a load above it. There's probably a lintel above most every door and window in your home, spanning the gap in the load-bearing wall. So, I'm really not sure what you mean by the term "Lintel Plate", or what, exactly, it is that you're wanting to do. Maybe some simple drawings or some pics would help. Rick
 
BeGreen said:
We've had a few lintel level block off plates installed. Take a look at this article for tips on installation. The links at the bottom are to some threads with images.

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

Ha! this is more or less what I want to do, I was using the wrong terminology. Thanks for the replies. I plan to modify the design so the rear of the block off plate sits a little lower than the front, to get some more deflection. Its a little tricky b/c i have an arched fp opening, but I plan on making a mockup out of cardboard to get the right fit, then go ahead with a metal one. Another question: this design says to use sheet metal. Any value in doing it with heavier gauge (say 1/8") metal?
 
BeGreen said:
We've had a few lintel level block off plates installed. Take a look at this article for tips on installation. The links at the bottom are to some threads with images.

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

Now that I've got my lingo straight and I've been able to access all this information, I have an insulation question:

The stove installer said they don't put in a block off plate to keep the flue warm for draft purposes and to reduce creosote buildup. I have a single wall SS flexible liner in there. If i put in a block off plate (w/ insulation above) will I be more at risk for chimney fires? Is it just a matter of cleaning more often? After a week with the stove installed I'm sure a plate will go a long way towards giving us some extra heat. The stove is a mid-80s Jotul 3 (non cat, pre EPA). From conversations with other owners of the same stove, they attest that it burns fairly clean for a stove of its vintage. Another option is to unseal the top plate and insulate underneath that to try and keep more chimney heat in the flue.
 
gparzych said:
BeGreen said:
We've had a few lintel level block off plates installed. Take a look at this article for tips on installation. The links at the bottom are to some threads with images.

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

Ha! this is more or less what I want to do, I was using the wrong terminology. Thanks for the replies. I plan to modify the design so the rear of the block off plate sits a little lower than the front, to get some more deflection. Its a little tricky b/c i have an arched fp opening, but I plan on making a mockup out of cardboard to get the right fit, then go ahead with a metal one. Another question: this design says to use sheet metal. Any value in doing it with heavier gauge (say 1/8") metal?

Not really. 24ga will work fine and is a lot easier to work with.
 
gparzych said:
BeGreen said:
We've had a few lintel level block off plates installed. Take a look at this article for tips on installation. The links at the bottom are to some threads with images.

https://www.hearth.com/econtent/index.php/wiki/Why_damper_seal_is_needed/

Now that I've got my lingo straight and I've been able to access all this information, I have an insulation question:

The stove installer said they don't put in a block off plate to keep the flue warm for draft purposes and to reduce creosote buildup. I have a single wall SS flexible liner in there. If i put in a block off plate (w/ insulation above) will I be more at risk for chimney fires? Is it just a matter of cleaning more often? After a week with the stove installed I'm sure a plate will go a long way towards giving us some extra heat. The stove is a mid-80s Jotul 3 (non cat, pre EPA). From conversations with other owners of the same stove, they attest that it burns fairly clean for a stove of its vintage. Another option is to unseal the top plate and insulate underneath that to try and keep more chimney heat in the flue.

Well, the liner should be insulated, especially for an exterior chimney. Then this is a non-issue. However, if you don't put in a block off plate, and the stove is in the fireplace cavity and not out on the hearth, about 75% of the heat from the stove is going to be heating that mass of chimney and not your house. Yes, you may need to clean more frequently, but that depends on the wood and how you run the stove. With good, well-seasoned wood and proper fire management (not smoldering), cleaning may not be an issue.

How tall is the chimney?
 
How tall is the chimney?

Chimney is about 20', always burning properly seasoned hardwood (went to a school in Vermont that heated part of the complex with wood stoves and a giant furnace that ate 6', 12" diameter logs, so I had some experience with wood at least, just not installations). Wish the stove shop had given me the option of an insulated liner, but there is certainly no money left to do much about that. After the first night of burning the stove I was thinking it was not throwing out as much heat as I'd hoped. I'm definitely going to install a block off plate (where do I get the insulation to put on top of that?). I was just outside looking at the outside of my chimney and daydreaming about removing a brick here and there and pouring in vermiculite to fill the airspace b/w the firebox and the exterior wall of the chimney. I can get vermiculite in bulk.
 
Try it for a season without insulating and see how it performs wrt draft and creosote build up. It might be ok. You will definitely notice a heating improvement with the block off plate, especially if you can add a small fan to stop heat from welling up in the fireplace. Lowes sells Roxul mineral insulation which will work fine for above the blockoff. In a pinch even un-faced fiberglass will work.
 
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