Is a block off plate beneficial with an insulated liner?

[Ansky]

Last month my jotul 550 insert was installed. I have an exterior 30' chimney. My liner is insulated and has a cap up top. using a flashlight and mirror, the insulation around the liner looks tight against the flue walls. But the insulation starts about 6' above where the old damper was...about 8' from the top of my fireplace.

I just don't know if a block off plate will provide any additional value, or would just be a waste of time building it.
Right now, the surround gets pretty warm to the touch, but not too hot to touch. And the brick above the stove gets warm too.

I just wonder if the insulation around my liner is doing a sufficient job of blocking off the heat from going up the chimney and a block off plate would not add any additional value.

Thoughts? Ideas?

 

[webby3650]

The installer should have blocked the flue around the liner at the top. This will help out alot, but a block off plate will help even more. The more heat you can keep from escaping the better!

 

[EatenByLimestone]

The block off plate stops a good amount of heat from entering the chimney. This heat will find its way into your home. If the heat went up the chimney will will only warm the chimney. A warm chimney isn't bad as it will stop creosote from condensing, but you installed a liner to help out with this problem. The heat from the stove might as well heat the house.

Matt

 

[Ansky]

I understand the benefits of a block off plate. I just don't know if it would add any value in my particular situation because my liner is wrapped in insulation that is pinned up against the inner walls of my chimney. The way I see it, no heat can escape up the chimney anyway because the insulation around my liner is stopping it from going up. Therefore, is a block off plate necessary?

 

[EatenByLimestone]

Does the liner 100% block off and seal the chimney or can heat escape around the corners? (Round liner, square flue)

Matt

 

[Hogwildz]

The block off plate will also keep more heat from being absorbed by the masonry of the chimney. The insulation won't stop that.

 

[Ansky]

Gotcha. Yeah, I'll do it. I was 80% sure I was going to do it anyway. I just wanted to make sure I wasn't wasting my time.
But EBL is right...I'm sure the existing insulation isn't blocking 100%. After all, the installers had to drop the insulated wrapped liner down the chimney, and if it was a super tight fit, then they wouldn't have been able to get it down the chimney without getting stuck.
I'll do it and post pics of the process.

 

[Hogwildz]

Wise decision, enjoy the benefits

 

[ddddddden]

Does the liner 100% block off and seal the chimney or can heat escape around the corners? (Round liner, square flue)

. . .EBL is right...I'm sure the existing insulation isn't blocking 100%. After all, the installers had to drop the insulated wrapped liner down the chimney, and if it was a super tight fit, then they wouldn't have been able to get it down the chimney without getting stuck.

You can also cram insulation, pref rockwool, in those corners between the terracotta flue tile and the liner, at the top & bottom of the flue. Then fill the smoke chamber and damper area with insulation and close it up with the block-off plate. Like any weatherization project, for max effect insulate to the hilt and seal well. Some folks like to insulate the fireplace around the insert too. If you're install is in an exterior chimney, you might want to do this. In an interior chimney, it doesn't matter much if you lose heat to the masonry.

I'll do it and post pics of the process.

Sweet!

 

[Mr A]

Room to work stopped me from getting a good block off plate in. Was a block off plate an option with your installer? When I mentioned a block off plate to local dealers, they all said they just stuff fiberglass insulation around the liner at the top of the chimney, had no idea what I was referring to. I manged to stuff some Roxul around the bottom of my liner at the smoke shelf and it did help get more heat into the room. I also used Roxul at the top.

 

[EatenByLimestone]

Stuffing insulation into the opening is a good start, but it won't stop the air from moving. It will only slow it down. It becomes an expensive air filter. It certainly is better than nothing though. One of the ways to find air leaks is to look for dark spots (trapped dust) in fiberglass insulation. The dust is trapped when air moves through it.

Matt

 

[JTP11]

Ansky,
My set up is similar to yours. I installed my 550 this past October with a 25' insulated SS liner running through an exterior chimney. I didn't add the block off plate or Roxul until about 5 weeks ago and I've noticed a significant difference in performance. I feel the Roxul and the plate are best used together. I put 2 layers of Roxul insulation above the damper, bolted the "poor mans block off plate", then lined the back, sides, and top of the stove with Roxul. Sorry I did't take any photos. Don't be shy about using a lot of Roxul, you get plenty of it in a bundle anyway.

The Roxul also made the 550 a little quieter.

 

[Trooper]

Gotcha. Yeah, I'll do it. I was 80% sure I was going to do it anyway.
I'll do it and post pics of the process.

Thanks in advance for posting the pics. I am considering a similar setup so looking forward to seeing yours.

 

[Ansky]

Ansky,
My set up is similar to yours. I installed my 550 this past October with a 25' insulated SS liner running through an exterior chimney. I didn't add the block off plate or Roxul until about 5 weeks ago and I've noticed a significant difference in performance. I feel the Roxul and the plate are best used together. I put 2 layers of Roxul insulation above the damper, bolted the "poor mans block off plate", then lined the back, sides, and top of the stove with Roxul. Sorry I did't take any photos. Don't be shy about using a lot of Roxul, you get plenty of it in a bundle anyway.

The Roxul also made the 550 a little quieter.

thanks. Where can I buy roxul? Do I ha e Togo to a specialty place, or does HD or Lowes carry it?

 

[EatenByLimestone]

I just picked it up at Lowes.

Matt

 

[JTP11]

Yeah, Lowes or HD. I got the Roxul that has an R value vs. the other Roxul they had for the Energy tax credits. A bundle was around $40.

Don't forget your new 550 qualifies for a 10% Energy Tax credit. (broken link removed to http://www.jotul.com/en-US/wwwjotulus/Tools/Whats-hot/)

 

[ddddddden]

https://www.hearth.com/talk/threads/insulating-behind-the-stove.104718/

 

[WoodpileOCD]

Ansky, My set up is similar to yours. I installed my 550 this past October with a 25' insulated SS liner running through an exterior chimney. I didn't add the block off plate or Roxul until about 5 weeks ago and I've noticed a significant difference in performance. I feel the Roxul and the plate are best used together. I put 2 layers of Roxul insulation above the damper, bolted the "poor mans block off plate", then lined the back, sides, and top of the stove with Roxul. Sorry I did't take any photos. Don't be shy about using a lot of Roxul, you get plenty of it in a bundle anyway. The Roxul also made the 550 a little quieter.

I also used the "poor mans blockoff plate" and it worked great. Easy to craft and install. Here are some pictures of my liner and blockoff plate install. Toward the bottom of the thread are some pics of the blockoff plate. Well worth the effort in my opinion. Good Luck. https://www.hearth.com/talk/threads...re-progress-fire-again-woohoo-new-pics.77014/

 

[Ansky]

Well, I did it. It took me half a day, but it's done and I fired it up and I definitely notice a difference. The surround it getting much hotter than before, and I don't even have a raging fire going. Here's some pics of the process...

Here's my supplies. I bought a 3'x3' piece of alluminum sheet metal. That's all HD had, and it cose me over $20.

Here's the cement and sealant I used.

Before pic...

Stuffed as much insulation as I could up there.

I made a template out of cardboard first and then transferred it to the sheet metal.

I had to cut it in half to fit it around the pipe.

Installed. Then I sealed up all the gaps and was good to go.

I did not, however, put the Roxul behind the stove or on the sides of the stove. I don't have a lot of space between the stove and the brick, so I didn't want to completely fill up that space and make the stove too hot.

So, how'd I do?

 

[WoodpileOCD]

Looks outstanding. I can't really tell but how is it attached to the brick. What's holding it in place?

 

[ddddddden]

To view this content we will need your consent to set third party cookies.
For more detailed information, see our cookies page.

Accept third party cookies

 

[Ansky]

Looks outstanding. I can't really tell but how is it attached to the brick. What's holding it in place?

Well, I tried screwing it in place, but that didn't work out too well. I tried pre drilling but apparently my mortar is super strong or something because I broke my drill bit and I couldn't get the screw in. I ended up simply bending the metal out a little more and laying a bead of fire block sealant in that gap. It was a tight fit in there anyway, but now the sealant will give it more strength. In about a week, after the stove has heated and cooled a couple times, I plan to pull the surround off and inspect everything...make sure everything is still good.