Block Off Plate ?

[pete97]

How much heat is lost on my BK Princess Insert without using a Block Off Plate in a masonry chimney? The chimney is lined with 6" Stainless Pipe and there is a plate blocking off or sealing off the flue at the top. Right now it is in the 20's here and I thought my living room would be much warmer with the insert in there. During the Shoulder Season it was plenty warm as we had to open the windows a lot from too much heat. Am I loosing heat up the chimney? I do have the surround installed around the chimney opening. Thanks Pete

 

[VCBurner]

I would think you're losing lots of heat without a block off! But, you should be able to burn that sucker hot, engage the cat and watch out. :coolsmirk: Load her up!!

 

[gizmos]

The guys on here will tell you that your loosing a ton of heat. It's a job, but well worth it.

 

[pete97]

Gizmos, what did you use for insulation around the pipe in your pic? Any templates for making the plate?

 

[VCBurner]

Gizmos, what did you use for insulation around the pipe in your pic? Any templates for making the plate?

That insul. is called mineral wool. One brand is Roxul. It is a super fire resistant/retardant insulation. Block off plates can be bought or made from at least non-galvinized sheet metal at least 24 guage thick. The SS is nice though! Measuring your openning would be the best way to make sure it'll fit.

 

[pete97]

Any ideas on where to buy the mineral wool and the block off plates?

 

[midwestcoast]

Any ideas on where to buy the mineral wool and the block off plates?

Sheet metal you can get nearly anywhere. The big boxes sell pieces & since you only need 1 small piece, price doesn't much matter.
Mineral wool is mainly only used in commercial construction now so --> local insulation places, contractors... I found plenty in my attic. Gizmos is very nice. Mine was cut with tin snips and bent with my gloved hands & a 2x4, doesn't look as nice, but with an insert you can't see anyway. It's air-tight. Seal the plate to the liner with furnace cement and plate to fireplace walls with hi-temp silicone or furnace cement.
Not a hard job. The folded edges make the fit fairly 'adjustable'. Pulling or disconnecting the insert will be the hardest part. Making mine was the first job I ever did with sheet metal.

 

[VCBurner]

Any ideas on where to buy the mineral wool and the block off plates?

Sheet metal you can get nearly anywhere. The big boxes sell pieces & since you only need 1 small piece, price doesn't much matter.
Mineral wool is mainly only used in commercial construction now so --> local insulation places, contractors... I found plenty in my attic. Gizmos is very nice. Mine was cut with tin snips and bent with my gloved hands & a 2x4, doesn't look as nice, but with an insert you can't see anyway. It's air-tight. Seal the plate to the liner with furnace cement and plate to fireplace walls with hi-temp silicone or furnace cement.
Not a hard job. The folded edges make the fit fairly 'adjustable'. Pulling or disconnecting the insert will be the hardest part. Making mine was the first job I ever did with sheet metal.

Very well put, I second that!

 

[midwestcoast]

You can make it totaally adjustable by making the liner hole an oversized square. Then make a smaller square that overlaps that hole by a few inches all around & make your snug liner hole in that. When you put the plate in place, the smaller plate can move around several inches to line things up, then fasten the 2 together with sheet metal screws & seal the joint (again with hi-tempp silicone or furnace cement). Hope that makes sense, guess I need to get to bed.

 

[W.B.]

The guys on here will tell you that your loosing a ton of heat. It's a job, but well worth it.

What kind of liner is that? It is oval correct?

 

[gizmos]

Yes, mineral wool. There is another product made you can use but I can't remember the name off hand.
Yes it is a 6" round liner that was ovalized.
Do some searches on block off plates, and you will find a ton of information on them.
I can't find my favorite one, if I find it later I'll post it for you.

https://www.hearth.com/econtent/index.php/articles/making_a_block_off_plate/

https://www.hearth.com/econtent/index.php/forums/viewthread/45633/P0/

 

[gizmos]

https://www.hearth.com/econtent/index.php/forums/viewthread/13710/

mineral wool, rock wool, or kaowool,

made from steel slag.

 

[golfandwoodnut]

It is debateable how much it helps, I wanted my installer to put one in, but he did not. Now I would have to take the insert out and put one in. I am not too worried about fabricating one, but getting the insert out with the surround, fire brick, etc. etc. seems like a pain. And of course, I have to put in back in. The installers comment was that it was sealed at the top and insulated at the top. He feels the chimney is a small space to heat and is not a big deal. Someday I guess I will find out if there is a difference, just another project that I have to put on the list.

 

[VCBurner]

It is debateable how much it helps, I wanted my installer to put one in, but he did not. Now I would have to take the insert out and put one in. I am not too worried about fabricating one, but getting the insert out with the surround, fire brick, etc. etc. seems like a pain. And of course, I have to put in back in. The installers comment was that it was sealed at the top and insulated at the top. He feels the chimney is a small space to heat and is not a big deal. Someday I guess I will find out if there is a difference, just another project that I have to put on the list.

Chimneys, especially ones that are exposed to the outside can suck up a lot of heat. Concrete walls will do the same.

 

[RedGuy]

With it sealed at the top I think the heat loss is pretty low, if not actually gaining heat from the liner. I don't have a block off plate yet and I don't belive I'm loossing much if any heat, though when my top plate came off the heat loss was incredibal! You could even feel the heat pouring out the chimney when I went up on the roof to resecure the cap.

 

[burntime]

I had mine installed with it. I removed and insulated with a block off plate and my chimney is in the middle of the house. I was getting ice damning so I was happy with the install but it was warming the attic too much. I can tell you without a doubt that insulating and block off plate have made a incredible difference. There is a HUGE difference in performance and heat. You can choke it down all the way where it was open a third before. You will use less wood and less heat loss. I even noticed the outer regions of the house were much warmer. If in doubt tear it out and do it. Well worth the piece of tin!

 

[pete97]

Thanks for all the info. I will get to it eventually. Too cold now to pull the stove out and let the fire go out !!

 

[backld]

The guys on here will tell you that your loosing a ton of heat. It's a job, but well worth it.

Gizmos, how did you cut that oval in the center of your block off plate? Thats almost too perfect.