# When is it OK to NOT insulate Liner, block off?



## Mr A (Feb 28, 2012)

Hello. After reading here a bit, I came to the conclusion that it is always a good idea to install a block off plate, and to insulate the liner. I have been around town today looking for Roxul that I have read about to insulate block off plate. I can't find any Roxul but for special order. I stopped into a hearth shop, they told me that they just stuff regular fiberglass insulation around the liner at top, and bottom, and no insulation needed in the middle. Winter is fairly mild here, it will freeze over night but daytime lowest temps are  mid 40's-50's. I was planning to do a block off plate, and full liner insulation, but after talking with the local installers at the shop, I'm wondering if that is necessary. I will be running SS liner through terra cotta clay liner. Existing chimney backs to uninsulated garage area, and up through attic. Liner is on the road and will arrive this week. Thanks.


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## blackdog1 (Feb 28, 2012)

I am interested in this as well...for insert going in existing brick fireplace on outside wall with clay liner.  Have talked to several dealers and 3 say just SS liner is fine and none of them use bottom block off (just stuff some insulation)...then there is one who explains they do install bottom block off and they recommend insulated liner and of coarse their the most expensive.  As a side note, how much more should it cost to have the block off done, I am assuming it is mostly labor?


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## DAKSY (Feb 28, 2012)

Over the ten year period that I installed chimney liners, we ALWAYS used
unfaced fiberglass. Never had an issue. No outgassing. No fumes.
No melting. No air leakage. Jam it in under the cap plate & make 
sure you get it on all sides. Jam it up into the damper area & make
sure you get all around the liner. You will create a standing column 
of dead air, & that dead air will ALSO act as insulation. Go for it. It's 
inexpensive, effective & safe.


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## Locust Post (Feb 28, 2012)

I would still say to definitely insulate the liner and the block off plate is more for your benefit than anything so the heat is not rising up inside the chimney. With the block off plate all the heat comes out into the room. I can tell you that I have an older insert that was a slammer install (just slid into the fireplace and then the surround panels) no liner or block off. I installed an insulated liner and just blocked off the opening with roxul. What a difference. Roxul around here can be purchased at Lowes. The draw back to fiberglass is it will turn white and get a little brittle over time but is probably safe to use.


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## Heatsource (Feb 28, 2012)

Here in N.ca the weather is pretty mild, top seal w/ ceramic wool is usually adequate in my experience. YMMV
I usually just use ceramic wool, but if the chimney is huge, i'll wrap the pipe w/wool and stuff the rest w/glass

I recently found melted fiberglass in the top of a lined chimney, so it is possible to melt regular fiberglass during chimney fires


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## Mr A (Feb 28, 2012)

Sounds a lot easier also! So, just stuffing fiberglass around the liner at the top and bottom is OK? Thank you for responding to my questions, much appreciated. The existing terra cotta liner is probably insulated with an air gap or vermiculite, as that is supposed to be standard building procedure. Are you guys saying to stuff insulation between liner and terra cotta, or to insulate the under side of the top plate, or both?


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## DAKSY (Feb 29, 2012)

Mr A said:
			
		

> Sounds a lot easier also! So, just stuffing fiberglass around the liner at the top and bottom is OK? Thank you for responding to my questions, much appreciated. The existing terra cotta liner is probably insulated with an air gap or vermiculite, as that is supposed to be standard building procedure. Are you guys saying to stuff insulation between liner and terra cotta, or to insulate the under side of the top plate, or both?



Jam it down along all sides of the liner UNDER the top plate.
You only hafta go down 5 - 6 inches to get the full effect.


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## BrotherBart (Feb 29, 2012)

Never could figure out why pros would pack the top and bottom of a liner install with the pink stuff, which is air permeable no matter how tight you pack it, leaks water and gets soft and sags when it gets hot but they won't wrap a liner in it.


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## Hogwildz (Feb 29, 2012)

Fiberglass does not stop air flow, thus won't crate dead air space. Don't care if pro or rookie says it does, that is just bullshit.
Do the job right, with the correct materials, and be done with it.
Block off plate is not that hard to make & Roxul and Kawool are pretty easy to find.
Most installers go the fiberglass route because it is cheap and less work.


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## Excavator (Feb 29, 2012)

Years ago, when the dealer sold me my 1988 Vermont Castings stove they convinced me to install it just using the slam method of 5 foot section of oval flex pipe up in to the 12 x 12 inch flue a foot or so and stuff fiberglass insulation around it to form a block off. I am lucky my house did not burn down with all the problems I had. Now 2 years ago I invested in the 8 inch liner and insulation kit and modded my damper frame to make room for the 8 inch flex liner. The stove performs like a new stove. Now I never get that smell of burnt insulation or water running down into my hearth. I made my own block off plate and used 2100 degree fire insulation around the block off plate to make good seal. It was not cheap but neither was my house or family. I did all the work on install and was not concerned about cutting corners or saving time.


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## EJL923 (Feb 29, 2012)

I have an interior 23' chimney which had all the tiles in good shape.  My liners not insulated and my flue stays plenty warm to not have to worry about creosote.  I have an insulated block off plate and also sealed the plate at the top of the chimney.  Sealing the top is important if your not going to insulate, helps retain heat.  If you have any questions about the integrity of your chimney or about the flue staying warm, just insulate and be done with it.  How did I know?  I didnt, i got lucky.  I had my insert installed before i knew the ins and outs of liners from this great site.  I knew the chimney was in good shape, and the installers just put in an uninsulated liner.  After three years, no problems with creosote.


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## Mr A (Feb 29, 2012)

Hogwildz said:
			
		

> Fiberglass does not stop air flow, thus won't crate dead air space. Don't care if pro or rookie says it does, that is just bullshit.
> Do the job right, with the correct materials, and be done with it.
> Block off plate is not that hard to make & Roxul and Kawool are pretty easy to find.
> Most installers go the fiberglass route because it is cheap and less work.


 Not so easy to find. I have to drive 100 miles to the nearest building supply that sells Roxul. Home Depot guy stares at me like I have three heads upon mentioning Roxul.


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## BrotherBart (Feb 29, 2012)

At Lowe's you can have Roxul shipped to the store with no shipping charge.


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## Hogwildz (Feb 29, 2012)

Mr A said:
			
		

> Hogwildz said:
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Many have found it on Ebay. Sorry I don't remember or have the links. Even a block off plate and good seal works well.


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## Eaglecraft (Mar 1, 2012)

Mr A said:
			
		

> Hogwildz said:
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Mr. A.

I suggest that you use only Roxul to insulate 1) the back side of your block-off plate and 2) also the inside of the top plate. Roxul is much better performing product than fiberglass. The following is from the Roxul web-page: "Roxul stone wool resists temperatures up to approximately 1177Â°C (2150Â°F). It can act as a fire barrier, when used in conjunction with a fire sealant material, against the spread of the fire and provides valuable extra minutes to save people and property, and reduce environmental damage."

2150 is about what your SS flex pipe is rated. Fiberglass will melt, Roxul will not, at least not at chimney-fire temps. Roxul is relatively unaffected by water. As you probably know, when subject to water, fiberglass turns into a soggy, useless mess.

Roxul is fire-rated, fiberglass insulation is not. See the fire-demo on the Roxul web-page, and no, I am not a Roxul salesman. And yes, you can purchase Roxul from Lowes. On the other hand, the folks at Home Depot know nothing about Roxul. I know this because I've asked them about Roxul. I think their ignorance is actually a ruse by Home Depot personnel because they don't sell the product and Lowes does.

I used Roxul to insulate both my block-off plate and my top plate. I also wrapped my 6 inch SS flex pipe with a foil faced insulation kit - and no, the insulation is not fiberglass, and no it's not Roxul. And yes, I recommend that you do insulate your SS flex pipe. You can purchase insulation kits from many SS flex pipe suppliers. Yes you can complete the project cheaper by omitting the block-off plate and the pipe insulation. On the other hand, those components don't add too much to the cost of the project, and those costs are off-set by the much improved performance of your wood stove and your exhaust system.

Good luck with your install.


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## branchburner (Mar 1, 2012)

One way of creating dead air space would be to use a perlite/cement mix, in combination with insulation (whether fiberglass or rock wool), to create plugs at both top and bottom. As DAKSY said,  jam insulation up into the damper area around the liner. Then from the roof, pour in some perlite/cement slurry. Then jam some insulation in under the cap plate, and put a few inches of slurry on top of that.

This is basically the same as just jamming in the insulation, but with the addition of having several inches of perlite/cement (being supported by the insulation, until it hardens), which will prevent air flow. It is partly how I earlier suggested insulating the entire liner, only it is leaving out the step of filling the entire air space with loose perlite.


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## Mr A (Mar 1, 2012)

My conclusion, It's like walking 10 miles barefoot, sure you can do it, but it's a better do do it with shoes on. Roxul=shoes!


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## Hogwildz (Mar 1, 2012)

Mr A said:
			
		

> My conclusion, It's like walking 10 miles barefoot, sure you can do it, but it's a better do do it with shoes on. Roxul=shoes!



Its like walking 10' on a 2100 degree blaze, you can do it with fiberglass shoes on which will melt & make and make a bbq out of your feet, or do it with Roxul or equivalent shoes and make it across.
Making whatever will work in some situations is done by everyone. When it comes to safety of one or their family & house, I suggest to over error on the side or overkill. Makes for better sleeping at night.
Wise choice, let us know how you make out.


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## Mr A (Mar 4, 2012)

Having huge problems installing. Can't get the liner tube to bend right to slip[ into insert, and no top or side room to work in. my face is black with soot, I'm tired. Going to have a beer and call it a night. Hopefully after a nights rest to get over the frustration, it will come together tomorrow. I really dont want to dig a hole to work in above the fireplace opening, any ideas? .


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## Eaglecraft (Mar 4, 2012)

Mr A said:
			
		

> Having huge problems installing. Can't get the liner tube to bend right to slip[ into insert, and no top or side room to work in. my face is black with soot, I'm tired. Going to have a beer and call it a night. Hopefully after a nights rest to get over the frustration, it will come together tomorrow. I really dont want to dig a hole to work in above the fireplace opening, any ideas? .



Mr. A:

Sorry that you are having difficulty making the pipe to stove connection. This is not an uncommon situation and many on this site have experienced similar problems. I slid my insulated 6 inch flex pipe fairly easily down a 13 inch by 13 inch flue - plenty of space. The only problem was getting the pipe past the damper (cut-out) opening. I had my better-half pull from the bottom while I pushed and guided from the top. Prior to the final wood stove and pipe install, I built a mock-up of the stove, having an appliance adapter to make sure that I could bend the pipe enough to connect to the actual stove when the stove would be positioned in its final place. Flex pipe is not as flexible as we would like it to be.

First, you will need an appliance connector to "easily" connect the flex-pipe to the wood stove. Easily is a relative term, but appliance connectors do make the job easier. If you don't have an appliance connector, get one locally or order one from the outfit that sold you the pipe. See, for example : http://www.chimneylinerdepot.com/store/427/product/Flex-Liner-ApplianceStove-Connector-6-inch.html. I installed my appliance connector to the stove first, and then then connected the pipe to the adapter. Finally, after the install was made, I covered all the connection joints with Rutland Stove cement - usually available from Ace Hardware.

Also a custom appliance connector can be fabricated by your local sheet metal shop - using only SS, of course- to custom fit the connection between the flex pipe and the stove. If you think that a standard appliance adapter will not work, make a mock-up of an angled adapter and give it to your sheet metal shop. You could use Quaker Oats tubes, or use aluminum vent pipe. I do not recommend using the type of adapter that "swivels" to different angles to allow the connection because these joints sometimes leak and sometimes break. 

Having two people make the connection does help, and it only takes a few minutes to make the connection once every thing is lined up.

Stay calm and good luck - you can do this.


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## begreen (Mar 4, 2012)

Mr A said:
			
		

> Having huge problems installing. Can't get the liner tube to bend right to slip[ into insert, and no top or side room to work in. my face is black with soot, I'm tired. Going to have a beer and call it a night. Hopefully after a nights rest to get over the frustration, it will come together tomorrow. I really dont want to dig a hole to work in above the fireplace opening, any ideas? .



Can you take some pictures so that we can see where you are at and what the options might be?


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## Mr A (Mar 5, 2012)

I didn't get to put in my nice block off plate,or  stuff the bottom with Roxul. The insert is small enough to push farther into the opening to align the straight liner to appliance connector. The connector in the pic has a nice angle and would probably work to enable the insert to be pulled out enough to be able to attach the surround, but it is 1/2" bigger than the liner. I had my 11 yr old nephew reach in the 2-1/2" space to align the connector. I packed Roxul around liner up top under the top cap. Local shop told me that is all they do, but with fiberglass.  It was 75 today, the weather changes quickly here. Last week was in the 50's. It will drop to mid 40's tonight, so I'll fire it up later tonight. This Jotul has a nice cast iron surround. I'm not sure if it is supposed to heat up and radiate,I wouldn't think so as it just connects to a sheet metal flange sticking out on the side. I would have liked a text book installation with block off plate, and surround attached, it's just not possible. insert needs to come out 6-1/2" to attach surround, liner wont bend to it. With surround only about 2" of insert body is beyond the face of the fireplace, with the rest in the hole. The doors open about 135 degrees. I may order a 45 degree connector   and try to get it pulled out, but for now, I'm going to live with it.


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## Eaglecraft (Mar 5, 2012)

Mr A said:
			
		

> I didn't get to put in my nice block off plate,or  stuff the bottom with Roxul. The insert is small enough to push farther into the opening to align the straight liner to appliance connector. The connector in the pic has a nice angle and would probably work to enable the insert to be pulled out enough to be able to attach the surround, but it is 1/2" bigger than the liner. I had my 11 yr old nephew reach in the 2-1/2" space to align the connector. I packed Roxul around liner up top under the top cap. Local shop told me that is all they do, but with fiberglass.  It was 75 today, the weather changes quickly here. Last week was in the 50's. It will drop to mid 40's tonight, so I'll fire it up later tonight. This Jotul has a nice cast iron surround. I'm not sure if it is supposed to heat up and radiate,I wouldn't think so as it just connects to a sheet metal flange sticking out on the side. I would have liked a text book installation with block off plate, and surround attached, it's just not possible. insert needs to come out 6-1/2" to attach surround, liner wont bend to it. With surround only about 2" of insert body is beyond the face of the fireplace, with the rest in the hole. The doors open about 135 degrees. I may order a 45 degree connector   and try to get it pulled out, but for now, I'm going to live with it.



Mr. A.: That's some awesome looking stone you've got there. A set of small hands and arms come in handy for stove installations. If you made a solid connection between the flex pipe and the stove flue - that's the main thing. You can only do what you can do.... The purpose of the surround is for aesthetics. It really doesn't have functional use. They don't fit tightly enough to prevent heat loss up the chimney and they don't add heat to the room.


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