Block off plate - how much temp rise?

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Cranford77

Cranford77

New Member
Sep 5, 2013
6
Had a Regency CI1250 insert installed recently. Stainless liner is insulated and runs up existing outside brick chimney, liner is capped at the top w/ std. cap. No block off plate or Roxul.

Using dry wood, 20% or less MC, loading unit full up to the top. Fan on unit doesn't turn on by itself until fire has been going a long time. Living room where liner is installed warms up but only a couple degrees.

Should also note that without insert running, the regular heating system keeps the house comfortable, so not a problem with drafty windows, etc. Also, only burning for several hours at a time, not continuously.

Is this kind of performance normal? I was wondering if anyone's had a similar experience, then added a block off plate with Roxul on top. How much improvement in the heat output did you notice?
 
With no insulation and no block off you can be losing a significant amount of heat straight up the chimney.

Combine that with your burning habits as stated (burning only for several hours at a time) and you have a situation where I can see you being disappointed with heat output.

Insulation and a block-off plate may lead to the fan turning on significantly sooner and you being more content with heat output. If you are only building a fire in the evening, loading it once, and letting it go out however don't expect a significant amount of heat output either though.
 
Just do it! I did it with Roxul stuffed up into the smoke shelf and where the liner passes through the damper. I even have more below the damper suspended with steel insulation hangers to form a nice seal. It makes a big improvement.
 
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Most folks get a noticeable improvement with an insulated block off plate in an exterior chimney. That's why we recommend them so frequently here.
 
I have an interior fireplace and noticed a 3 degree improvement right off the bat. An exterior fireplace would probably benefit more.
 
Thank you everyone to all the replies, this forum is really a big help. I hesitate to go for the block off plate & insul. b/c of the work.

I'm going to try heating a 600 sq ft area of the house for the better part of a day with just the insert running (turn off regular heating system) and see what happens.
 
Keep us posted...
 
We have seen cases here where folks were ready to dump their insert before putting in the block off plate. Afterward most reported good heat and a dramatic improvement in heat coming out of the stove. How good your gains will be depends on the fireplace and chimney + insert, outdoor temps, etc..
 
begreen said:
We have seen cases here where folks were ready to dump their insert before putting in the block off plate. Afterward most reported good heat and a dramatic improvement in heat coming out of the stove. How good your gains will be depends on the fireplace and chimney + insert, outdoor temps, etc..
Click to expand...

This was the first thing I learned from the folks here when I began my research several years ago and boy am I glad I did. The so called installers in my area tell everyone they don't need to do it, but what I heard here made sense so I figured I would give it a shot... IT WORKS! I have helped many of my friends do it and they swear by it as well. Even helped a buddy pull his professionally installed stove and ad one. He is now very happy with his stove. Just a lot easier to do it right the first time and sit back and enjoy the results.
 
If the plate is intimidating then Just do the roxul. It's only around 40 bucks and it's a easy as just taking the surround off and shoving it into the damper area. There should be a shelf in there that you put it above. I was able to keep my insert in place. When you put it in you'll realize that it's not comming down, and you can do the plate at a later time if you need to. It helps a lot because with totally flush inserts it's hard to get the heat into the room and not up the chimney. Good luck.
 
Is this the roxul "safe and sound" version of the insulation? Should you stuff this just under the rain cap at the top of the chimney as well? Thanks all.....
 
Ram 1500 with an axe... said:
Is this the roxul "safe and sound" version of the insulation? Should you stuff this just under the rain cap at the top of the chimney as well? Thanks all.....
Click to expand...


I used Roxul "firestop" insulation from an insulation contractor. They gave me a piece so it had no packaging. I used it under the top cap because I had enough left from above the block off plate so I figured what the heck. Centered the liner up nice in the existing chimney.
 
The top of the liner inside the chimney above the roof line is likely to cool off more than the part of the liner that is inside the structure of the house. So,yes, I think that is a good area to add insulation. When I installed my system I put about four feet of insulation around the liner right below my top cap. I also installed a block off plate inside the fireplace with insulation sitting on top of it. I'm getting great heat with the set up.
 
I still haven't done a blockoff plate either. I would have to do it in 2 pcs because I don't want to remove the liner from the stove to do it, and it seems like a pain... so the roxul thing might work for me.
I do have a nice large 2" thick piece of the fireproof felt though (Kaowool), unused, from a friend who works in a metal forge, that I intended to put on the back of a blockoff plate, could I stuff that in there instead or is that a worry due to fibers potentially getting loose?
 
tickbitty said:
could I stuff that in there instead or is that a worry due to fibers potentially getting loose?
Click to expand...

That is one potential concern. Another is the "permanence" of the insulation. Fresh from the bag insulation has quite a bit of "spring" in it. It will generally stay where you squish it into. 10 years down the road and all bets are off.
 
Jags said:
That is one potential concern. Another is the "permanence" of the insulation. Fresh from the bag insulation has quite a bit of "spring" in it. It will generally stay where you squish it into. 10 years down the road and all bets are off.
Click to expand...
The kaowool is more like a felt blanket than an insulation texture, so I don't think it would pack down, but I'm guessing it wouldn't be safe to have it stuffed in the hole without a good covering.
 
tickbitty said:
The kaowool is more like a felt blanket than an insulation texture, so I don't think it would pack down, but I'm guessing it wouldn't be safe to have it stuffed in the hole without a good covering.
Click to expand...
Yeah - my response was more in line with the Roxul ins.
 
Roxul firestop insulation, (not sure of proper name) is what is used where there is a void such as between joists that extends over finished space. Code in my area will let you leave this product exposed . I have used it where there open joists that extend over a finished portion of a basement where it is impractical to install blocking. It comes in batts but is considerably more dense than say a fiberglass. Any good insulation contractor should be able to sell you a piece.
 
Rudyjr said:
Seems to me I heard from someone that the fibers from Kaowool can be pretty nasty if they get airborne. Don't know if thats true or not but I would check.
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It is true and the stuff can be an irritant. Other than the time and a couple of bucks worth of material, there is really no down side to a blockoff plate. You can ultimately use the lightest gauge stuff you can find. It will work up with a pair of tin snips and a pair of pliers. Easy stuff to do. And it makes it very easy to seal around.
 
How about for those of us with inserts in a ZC fireplace? My liner is insulated and my installer was muttering about how tight a fit it would be the whole time. Does this type of installation change the equation?
 
Andy S. said:
How about for those of us with inserts in a ZC fireplace? My liner is insulated and my installer was muttering about how tight a fit it would be the whole time. Does this type of installation change the equation?
Click to expand...

Maybe - it all comes down to letting heat up the chimney. If you are not letting heat up - then no problem. If you are - potential problem. Without putting eyeballs on your specifics I wouldn't be able to give a very good assessment.

Edit: and there is some validity to the internal vs external chimney argument. Depending on design - if internal - there are some situations that you might WANT a warm chimney.
 
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