To Insulate or Not Insulate a Flexible Liner - That is the question!

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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
I have been debating the use of insulation on a flexible liner and I have received mixed opinions from some people and the sales reps. It seems that insulation is required from most insurance companies to maintain safe clearances rather than stack temp and creosote- although stack temps and minimizing creosote formation is important to maintaining a safe chimney and reducing a hazard. I do know that an item MUST be installed in accordance with the manufacturer’s installation instructions to maintain the item's listings and codes. From what I have been reading recently, the insulation is required in masonry non-lined chimneys and lined chimney’s (no cracks) if the chimney has 4 inches or less thick masonry and contacts a combustible material. So, a properly code compliant chimney, with no cracks and more than 4 inches of masonry is all right to use without insulation. The insulation provides the 1" clearance and zero rating to the 4 inch or less masonry in case the SS liner is in contact with the masonry. Duraflex has a 1 inch spacer clamp (assumed to be used with Thermix pour in insulation) to provide a 1 inch spacing. The clamps are placed every 5 feet of length. One article says that most pour-in insulation jobs are not performed correctly, and make a deteriorated liner very difficult to remove. http://www.chimneys.com/articles/listed-chimney-liner-insulation-that-doesnt-work
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,130
central pa
I say always insulate There is no down side to insulating and there are many benefits. And honestly in most cases (if not all which I have been debating) it is required by code when using it for solid fuel.
 

mrdinks

Member
Oct 30, 2014
17
Iowa
My chimney runs up the center of the house from the basement and was an open fireplace in good working condition. I put in an insert with an uninsulated flex liner.
I always had smoke issues so last year I tore out the liner and installed a new insulated liner and can say it made a big difference.
Like I said it is an interior chimney any people say they are warmer.
So I am a believer in the insulation.

Sent from my Samsung
 
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buc74

Burning Hunk
Oct 16, 2012
100
Fort Atkinson, WI
Both the sales reps advised not to insulate and was a waste of my money. Due to fact my chimney was interior. I will insulate though. It almost seems like the installers just want to mess with it?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
22,130
central pa
Both the sales reps advised not to insulate and was a waste of my money. Due to fact my chimney was interior. I will insulate though. It almost seems like the installers just want to mess with it?
Yes many installers are just lazy. That and it is easier to make the sale if you keep your price down and omit the insulation. Did they even check or ask if you had proper clearances?
 

heavy hammer

Minister of Fire
Jul 18, 2015
1,665
Kirtland Ohio
Insulate it if going to put in a liner just do it once. Would not be a lot of fun to pull it out to insulate in a year or so, plus as others have said it is code in many areas. I just installed my pacific energy summit insert a couple weeks ago, insulating the liner only adds a little time.
 
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Smoked

Feeling the Heat
Feb 19, 2015
367
Roanoke VA
Agree, insulate it. Better draft, easier to clean. Warranty may not be valid if not in some cases too. I did a pre-insulated one last fall. Was pretty heavy to DIY but was about the same price as liner plus wrap and did not have to mess with the process of wrapping. Tomorrow may be a good day to brush some pipes!!
 
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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
I was looking at the pre-insulated type- but someone said they weren't any good. I also like the thought of the .018 thickness over two layers of .006. The single wall pipe appears very fragile and now that I have my damper frame cut I think the heavy flex is the way to go.
 

VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
Agree, insulate it. ..... I did a pre-insulated one last fall. Was pretty heavy to DIY but was about the same price as liner plus wrap and did not have to mess with the process of wrapping......
Is the pre-insulated pipe strong?
 

kennyp2339

Minister of Fire
Feb 16, 2014
5,134
07462
My take is that you only want to do the job once, go with the heavy wall insulated
 
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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
Thanks Kenny. I was told by a salesman that I cannot use the deluxe terracotta cover with the heavy wall because the pipe is too heavy. I do not like the look of the materials required to trim off the heavy wall. The heavy wall flex requires the top plate, pipe strap, storm collar, and rain cap. Are there any alternatives to the trimmings for the heavy wall flex?
 

kennyp2339

Minister of Fire
Feb 16, 2014
5,134
07462
The top plate is specifically made to anchor / support the liner center, it can be trimmed to fit over the clay flue tile seamlessly, it will also keep the weather out between the liner and chimney, the rain cap can be changed to a style you like, its only a cap that has a clamp on style mounting process, using a large metal hose clamp (pipe strap) the rest of the liner goes into the chimney and connects to your insert via stainless steal appliance adapter.
Some on the uneducated sales staff try to over sell there products, perhaps to steer customers towards a product the staff uses all the time because there familiar with it. The main question I would ask is what type of flue do you have, how many bends, what size opening, do you have a smoke shelf that needs to be chiseled out, or a metal damper that needs to be removed? That would really determine what type of liner you need, if there's a offset or ob'd long area then you might be forced to install a more flexible liner, if the clay tiles are say 7x7 then you may need a uninsulated liner then pour in type insulation. There are just to many variables to go through without knowing specific info, FYI - Bhollar is the go to guy when it comes to this stuff, he's a pro and gives great info.
Just a quick question - are you considering a block off plate? I would def look into that
 

ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
Iron, I would definitely recommend the Heavy Flex. I just installed a 22ft section on Saturday (2 days ago) and it is a lot harder because the weight but it will be worth it. I installed the Easy Flex 2 weekends ago in another chimney and it went really well, very easy job but the difference was the quality of the pipe. Heavy Flex is hands down soooooooo much more rugged and durable. By the way, I know it's popular to suggest the Heavy Flex is not flexible but it is very flexible......not as much as the Easy Flex but still very flexible.

Now suggestions on the top cap ect.... You have many options but as Kenny said, we need more details on you chimney. What size is your flue, inner and outer diameters? Clay Liner? The top plate and clamp they sent with my Heavy Flex liner were in my opinion....weak. I modified things and added additional support. If I were doing it again I would simply fabricate a 1/8 inch plate Stainless Steel (SS) plate with a cut out in the center for the pipe and use it on top my clay flue. I would also fab my own clamp using heavier gauge SS. I placed a full sized SS cap that covered my entire flue not just the pipe. I had to cut down my top plate to do this and strengthen the entire support but worth the extra work because it looks much better. I plan to post pics of my install when I am complete. I still have to get the Stove in place and make final connection to pipe.

Also I second the block off plate. I fabricated mine out of sheet metal and it turned out great!
 

VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
damper.jpg damper1.jpg raincap.jpg - Kenny, my flue is a 10x10 terracotta straight up with a slight offset at the smoke chamber. The height is 11.5 feet from the top of the flue damper, 12 + feet in total height from the lintel and the proposed T connection area.
- CCMAC, please post your photos. I am thinking that 13 feet of heavy may not weigh that much and maybe I can use the deluxe terracotta rain cap seen here. raincap.jpg

I am planning on blocking off my damper area with sheet metal
 
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ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
Yes you can use that cap. That is the cap I have. I'll try and snap some photos this evening. You will need to modify the top plate. The reason is because the top plate is approx. 3+ inches then the clamp is another 1.5 inches.....so 4.5 inches of height doesn't leave more than 3 inches below the cap! I had to cut the top plate down and then beef up the plate with an additional plate under it. If I was doing it again I would've just fabbed up a stainless steel plate maybe 1/8 inch thick and used it instead of the cheap plate they sent.
 
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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
Yes you can use that cap. That is the cap I have. I'll try and snap some photos this evening. You will need to modify the top plate. The reason is because the top plate is approx. 3+ inches then the clamp is another 1.5 inches.....so 4.5 inches of height doesn't leave more than 3 inches below the cap! I had to cut the top plate down and then beef up the plate with an additional plate under it. If I was doing it again I would've just fabbed up a stainless steel plate maybe 1/8 inch thick and used it instead of the cheap plate they sent.
Instead of 1/8 inch plate, I wonder if the flat plate they sell will fit underneath this rain cap to reinforce it? Although I am told you need to secure the heavy flex with the HD bar clamp and not standard internal pipe clamp.

http://www.woodlanddirect.com/Chimney/Chimney-Liner-Parts/Flat-Top-Plate-13x13

top plate.jpg
 
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ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
That is very similar to what they sent me only mine was slightly convex toward the center hole. You see how high the circular rise is on that.....that is what I had to cut down. If I didn;t then once the clamp goes on top you essentially have allowed only about 3 inches of space between your pipe and the top of the rain cap. Not really ideal so rather than have issues I cut it. The pipe will be significantly lighter at 13ft. I would also call them and see if you can get just the amount you need. Even if it is $50 cheaper than buying the 25ft section...that'd be money saved. Plus my actual pipe was literally 27ft.
 

VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
That is very similar to what they sent me only mine was slightly convex toward the center hole. You see how high the circular rise is on that.....that is what I had to cut down. If I didn;t then once the clamp goes on top you essentially have allowed only about 3 inches of space between your pipe and the top of the rain cap. Not really ideal so rather than have issues I cut it. The pipe will be significantly lighter at 13ft. I would also call them and see if you can get just the amount you need. Even if it is $50 cheaper than buying the 25ft section...that'd be money saved. Plus my actual pipe was literally 27ft.
Typically, the length comes in 25 feet. So, I put my safety glasses on and "worked my pencil" while figuring I would purchase enough to do my chimney 2 times @ 30 feet and that would only cost me about $115 more for the liner, unless they read this and change their prices. The insulation kit is only offered in 25 feet lengths, so I was going to purchase that from a competitor that has a 30 or 35 foot length, which means the additional materials "2X" would only cost me about $200 more-without the additional caps, terminations, and T connector- now remove safety glasses.
 

ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
Here's mine. Again, I actually have two plates under the cap because the one sent to me was really not up to the job. You can only see the top plate in the photo.
 

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ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
Here's a close up.
 

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ccmac

Burning Hunk
Jan 1, 2014
200
Indiana
And last view.
 

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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
Here's mine. Again, I actually have two plates under the cap because the one sent to me was really not up to the job. You can only see the top plate in the photo.
CCMAC, That is a nice looking install. Did you order the whole kit or did you order alacarte? My understanding is the included top plate is supposed to be much heavier for the heavy flex.
 
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VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
CCMAC, Did you order the whole kit or did you order alacarte? My understanding is the included top plate is supposed to be much heavier for the heavy flex.
Nice rain cap. Were the two extra plates the same ss from the same retailer/wholesaler?
 

VirginiaIron

Minister of Fire
Dec 19, 2013
1,072
Central Virginia
Are the lower (hidden) plates raintight? It looks like there is a gap in the opening around the flex liner.
 
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