No Block Off Plate - Is That OK?

[BrotherBart]

Block off plates are the membership fee for hearth.com. You vile have ze block-off plate!

I have one because my stove is a free stander in the fireplace. If it was an insert there would just be rockwool packed around the liner where it passes through that thick cast iron box called a damper frame. I have a hard time believing a piece of tin holds heat any better than that quarter inch cast iron and the liner shroud. And if something happens in that chimney that will blow out the rockwool and blast the surround off of the front of the fireplace then it would blow a block-off plate into next Tuesday also.

Sometimes I miss having this argument with Elk.

 

[Jerry_NJ]

BrotherBart, you say "rockwool", can you recommend anything in particular? Is there a form of rockwool in a blanket type form, or other forum that would support wrapping it around the pipe at the masonry damper opening? Can I get something at Home Depot aor Lowes?

Stanleyjohn, I assume your are referring to my old Golden Retriever (in my avatar), that suffered a stroke last August. He is doing much better and gets around on his own now, can even negotiate a few stairs up and down. He tires easily and is a little unstable, but then the same is true for me. Thanks for asking.

 

[BrotherBart]

BrotherBart, you say "rockwool", can you recommend anything in particular? Is there a form of rockwool in a blanket type form, or other forum that would support wrapping it around the pipe at the masonry damper opening? Can I get something at Home Depot aor Lowes?

None of the home improvement stores sell any form of it. Lots of it shows up on eBay as Kaowool blankets. I used batts of 2300 degree rockwool that is sold for sound deadening. For the life of me I can't remember the brand. I put it on top of the block-off plate and packed the top four or five feet of the chimneys with it. I lucked into a bundle of it at an airline bankruptcy auction. It is nasty short-fiber stuff and a respirator should be worn when you are handling it.

 

[jwscarab]

I ran my old stove for 3 years w/o a block off plate. Never had one - didnt know any different.

When the T6 arrives, I definitly plan on installing a block off plate during the stove install, It free standing in front of a fireplace.

Interesting enough - I was advised to definitly install the block off plate - but NOT to insulate between the 6" ss liner and the 9x12 clay. And I was leaning on doing that too.

External stack - 32ft.

 

[Jerry_NJ]

Hum, my stack is about 32 feet too, and I have an insulated 6" ss liner, in an external masonry chimney, tile is about 9x12, don't remember at the moment.

jwscarab, you say no insulation? this is contrary to all the advice I've received over this forum and from two installers who bid on the job at my house.

 

[jwscarab]

Yea I have to admit I was a bit suprised. My ss liner is part straight and part flex - to get around a bend or two - so thats why it was not insulated for the get go. I was leaning on pouring that insulation in from the top after the block off plate was installed. The person who recomended against it is a respectable person in the business so I have to admit I was suprised by his reply.

His reasoning had to do with the liner only touching the insulation at a small point of each insulation pellet - and the air void between pellets. I cant remember if he said it would reduce liner life?? Temp difference where touching/not touching?? I know I am not being of much help - bad memory. I will ask again for an explanation and reply.

 

[Jerry_NJ]

I believe the pour-in insulation is mixed with water and it goes in a bit like cement. I'm not saying there are no granules, but more like an aggregate with fine stuff between the bigger pieces. I have never seen the pour in and while I was interested in it as it seals to whole masonry space, I didn't because it was rather expensive. The insulation sleeve wasn't cheap, something like $300, I can look up if we need to know. The pour-in insulation is more-or-less permanent, i.e., you can't just pull the liner out if you want to go back to the original fireplace.

 

[branchburner]

Yea I have to admit I was a bit suprised. My ss liner is part straight and part flex - to get around a bend or two - so thats why it was not insulated for the get go. I was leaning on pouring that insulation in from the top after the block off plate was installed. The person who recomended against it is a respectable person in the business so I have to admit I was suprised by his reply.

His reasoning had to do with the liner only touching the insulation at a small point of each insulation pellet - and the air void between pellets. I cant remember if he said it would reduce liner life?? Temp difference where touching/not touching?? I know I am not being of much help - bad memory. I will ask again for an explanation and reply.

There are two ways to pour in perlite:
1) loose/dry, and that has the major drawback that if it finds even a tiny way through the blockoff plate it will sift down like sand through an hourglass into your hearth.
I did also hear the reasoning that the pore space between the grains would leave the liner uninsulated at those minute gaps, and thus the liner would heat differentially and some of different alloys would separate and the liner would be weakened and blah blah blah... I wasn't buying that - if you use a ceramic fiber blanket, is every tiny bit of stainless steel in contact with insulation? I would think not. There must be some void space with that stuff, too. I could be wrong, but I think it's a line from someone who wants to sell a blanket for $300. Perlite can be had for $2-3 a cubic foot, so you could do the job for maybe $50.
2) mixed/wet (meaning it is combined with water and mortar or something, I guess), and that has the major drawback as mentioned that once it dries, you're pretty much stuck with it.
If you were doing this, I don't know why you'd need the stainless steel - you could just have some sort of removable tube as a form, pour your slop in around the outside of the form, then remove the form and your hardened slop would be your liner. This strikes me as the cheapest way to go, but it is permanent!

 

[branchburner]

I believe the pour-in insulation is mixed with water and it goes in a bit like cement. I'm not saying there are no granules, but more like an aggregate with fine stuff between the bigger pieces. I have never seen the pour in and while I was interested in it as it seals to whole masonry space, I didn't because it was rather expensive. The insulation sleeve wasn't cheap, something like $300, I can look up if we need to know. The pour-in insulation is more-or-less permanent, i.e., you can't just pull the liner out if you want to go back to the original fireplace.

I think the pour-in stuff is expensive if you buy it pre-mixed, but I bet you could find a recipe and homebrew it really cheap. I couldn't believe how inexpensive perlite was at my local masonry supplier ($9 for a 4 cu ft bag).

 

[Jerry_NJ]

There's the check, two people say perlite is cheap, must be the installer didn't want to do that approach. My reason was we had some chimney smell we couldn't get rid of, we had a locktop installed to seal off the chimney, I removed the "slammer" and junked it, had the chimney swept and rotary cleaned, still some smell. Well it seems that with the installation of the ss liner with insulation wrap, and the resulting knocking down of more creosote/whatever, the smell has mostly gone. Hope it doesn't come back when I fire up the new insert...if it does I'll be back on square one, guess I could pour the perlite in with a block off plate.

 

[branchburner]

There's the check, two people say perlite is cheap.

Well, I'm really just one person who posted 2x, but it is cheap.

If you get it in 4" thick batt form, that rock wool is cheap, too. I got some stuff called Thermafiber, the stuff used for fire containment in commercial construction (they call it "safing"), I think it was $40 for 5 2'x3' sheets. I belive they make 1" residential stuff, sold as soundproofing, under the Thermafiber brand as well. I wish I had checked into that - 4" was too thick for my purpose and I was tearing it into hunks and making a mess.
I imagine you could make your own insulation blanket from the one inch stuff for a lot less than $300!

 

[RedRanger]

Block off plates are the membership fee for hearth.com. You vile have ze block-off plate!

Sometimes I miss having this argument with Elk.

Fine then =go ahead and argue with me. 10 hours burning-temp outside-37F- rec-room (15x26) 88F and I am off to bed, too damn hot down there. And the Bear was just cruising, not opened up at all cept for the initial first 30 minutes. And here is another question for ya?

Tested and retested my thermometer on the top of the insert(vis-a-vis) oven test/ it is positive. Or could it be cause of the 5/16 steel on the top of my beast, that is why my secondaries kick in at only 350?? Like if the steel on the top was only like the "cheapies" 1/4" on top would that make a diff?

Or maybe I should just hang up the Heinikens and not annoy you anymore tonight?? ;-P

 

[jwscarab]

Well, per the original topic (sorry we got off an a tangent), I am definitly going to install a lower block off plate.

I do intend to talk to this guy one more time on the insulation, to better understand his reasoning, but I will lean towards doing it unless he conviences me otherwise.

Money never grows on trees, but in areas like this - I prefer to spend the $ and do it right - not have $ be a deciding factor.

 

[begreen]

Block off plates are the membership fee for hearth.com. You vile have ze block-off plate!

Sometimes I miss having this argument with Elk.

Fine then =go ahead and argue with me. 10 hours burning-temp outside-37F- rec-room (15x26) 88F and I am off to bed, too damn hot down there. And the Bear was just cruising, not opened up at all cept for the initial first 30 minutes. And here is another question for ya?

Tested and retested my thermometer on the top of the insert(vis-a-vis) oven test/ it is positive. Or could it be cause of the 5/16 steel on the top of my beast, that is why my secondaries kick in at only 350?? Like if the steel on the top was only like the "cheapies" 1/4" on top would that make a diff?

Or maybe I should just hang up the Heinikens and not annoy you anymore tonight?? ;-P

sonny, seems to be a strong indication that you need to work harder at getting that heat distributed upstairs. But methinks perhaps this is not relevant to the question of value of a block off plate for those in different circumstances?

 

[Jerry_NJ]

Boy am I on the "fence", I have a new installation on an Quad insert and no block-off plate. This was not even in my thinking process following the discussion with the installer who didn't recommend, maybe didn't offer, a block-off plate.

My insert is in a large masonry fireplace with lots of outside brick, part of a three flue/chimney brick-works. Still, like sonny, my experience of no block-off plate, even worse I had a slammer, is that there is a lot of heat coming out of the insert in spite of what is lost into the chimney. I hope for a lot better result with the new insert at it has the full SS liner and closed off top. Still, I'll keep an eye out for some high temp rockwool blanket material to plug up the chimney, sort of a soft block-off.

 

[Jags]

Why would you NOT want to. Give me one good reason. 'nuff said.

Here is a good reason. When I went to bed last night the rec-room 15x26 was 88F. I really don`t want it any hotter than that. Exterior chimney,full liner and chimney cap, no block off plate. "And no, I wasn`t running the bear wide open last evening"..

Oh, and the temp outside was 37F.

Sonny, the difference between most installs and yours is that you WANT to loose heat. Most are not in that situation.

p.s. an open window will do the same thing

 

[stanleyjohn]

Ok!Simple solution!! If you dont have a block off plate and getting plenty of heat even on the coldest days and nights!dont install one.It may be better in your case if you dont and have a ss liner thats not insulated!That extra heat going up the chimney will keep the pipe warmer and help prevent creosote build-up.