Please help me make sense of chimney liner and insulation choices!

[staceyneil]

We are installing a Vermont Castings wood-burning fireplace insert into an existing brick fireplace/chimney. The (c.1956) chimney is in the middle of the home (not exterior) and lined with ceramic tile.

This is a DIY project, and money is tight. But we want to do it right. We're definitely going to install a SS chimney liner (probably flexible due to cost.) Multiple sources say we don't technically NEED to insulate this liner... then again lots of people say we should.

Questions:
1) Is it OK to buy simply the cheapest flexible SS liner at one of the various chimney-liner places on line? Look like about $275 for a 6", 15-foot kit we'd need...

2) Insulation: first of all, go ahead and comment on whether it's needed or not! DH says no, let's not . I'm not sure. If so, iit sure looks like using a pour-in insulation like Thermix is a WHOLE lot cheaper, and possibly also easier, than the blanket-wrap stuff. By my caclulations we'd need only 2 bags of Thermix at $75 each versus a blanket-wrap kit at $275. We're already planning to make a bottom close-off plate for the flue. Is there some reason why the Thermix is not a good idea? I also know that we might have trouble getting the blanket-wrapped 6" pipe through the very top of the chimney (which is only 6" as opposed to 7.75" for most of the chimney) so it seems easier to pour something in. Are there other insulation possibilities we haven't looked at yet?

Thanks for any advice!

Other maybe pertinent info:
location is coastal Maine
house is one story, length of chimney liner needed= 15 feet

 

[begreen]

Often the cheapest liner is not the best, especially if the metal is thin. Get a good quality liner, this is infrastructure. In this situation, I'd be inclined to skip the insulation, especially if the clay liner is in good condition. Be sure the chimney is thoroughly cleaned before starting. That is not optional.

 

[pen]

Often the cheapest liner is not the best, especially if the metal is thin. Get a good quality liner, this is infrastructure. In this situation, I'd be inclined to skip the insulation, especially if the clay liner is in good condition. Be sure the chimney is thoroughly cleaned before starting. That is not optional.

I just installed the liner I purchased from a guy on here named "TheHeatElement" It's a magnaflex liner. 400bux total for 20 feet of 316ti stainless, 1 section of ss rigid liner, cap, rain collars, ss elbow, etc. He even included some insulation for placing around the the top and bottom of the liner.

I insulated mine by using vermiculite. I bought it for 14.95 for a 4 cu ft bag. I used 3 cubic feet filling the area around the 6 in liner. My tiles measure 6 3/4 inches inside diameter square.

I paid theheatelement on a saturday evening and the product was at my home wednesday. Communication before and after has been great. I am really can't say enough about the product.

pen

 

[staceyneil]

Oh, thank you! So what do you think of the standard 316ti 0.06" liners, like FlexKing or Simpson DuraFlex 304 or M-FLex or others with those specs? They seem to be a step up from the .005" thick ones, but not super fabulous like the "pro" or double-walled ones. Can we stick with the 0.06" type?

 

[branchburner]

I insulated mine by using vermiculite. I bought it for 14.95 for a 4 cu ft bag. I used 3 cubic feet filling the area around the 6 in liner. My tiles measure 6 3/4 inches inside diameter square.

Definitely the cheapest way to insulate. I used perlite, a similar material. But with an interior chimney, you could skip it - as long as there is a good seal at the top and at the block-off plate, you will have dead air space.

 

[begreen]

Oh, thank you! So what do you think of the standard 316ti 0.06" liners, like FlexKing or Simpson DuraFlex 304 or M-FLex or others with those specs? They seem to be a step up from the .005" thick ones, but not super fabulous like the "pro" or double-walled ones. Can we stick with the 0.06" type?

DuraFlex SS is a first class product. A 15' kit for 304 is about $280, 316Ti about $328. Both are .005 wall.
http://www.northlineexpress.com/multiple_items.asp?cc=6LDuraFlex

 

[oldspark]

How big is your liner now, I am using a round 7 1/4 inch clay liner for my summit and it works fine.

 

[staceyneil]

Thank you!

Any reason to not use 304 SS? Less $$ is always better

Measurements: my husband measured the clay liner at 7" x 10.75" when I asked him to get me measurements so I could see if we technically needed to reline. He's not here (at sea) so I can't ask him, but I assume he took that measurement by reaching down inside the chimney.... because when I was up there the other day, I noticed that the top opening -it has some sort of narrower clay collar I guess- measured only 6" on the narrow side. Not enough to pass a blanket-insulated 6" liner pipe through, I wouldn't think! So- I am glad to hear we don't need to insulate it!

I do see that folks insulate the top part sometimes. To help with draft maybe? Would that be advisable in our case? There's maybe 3 feet+ above the roofline, and of course also 4-5 feet or so in the (unheated) attic space. If it IS advisable to insulate the top few feet, I assume some type of high-temp insulation is needed. Can you advise? I'll be ordering some from eBay to make the block-off plate insulation, anyway.

 

[staceyneil]

Sorry: I just saw some of the earlier posts.
Where are you guys getting the perlite or vermiculite? Is it the same as for horticultural use (ie garden supply)? And do you just pour it right in? (I'm thinking it's those little teeny white balls, really light, right? Looks like styrofoam sort of?)
You are SO much help, I really appreciate it. I spent about 4 hours coming the web for info yesterday, tearing my hair out... I should have come here first

 

[begreen]

Insulating the top exterior portion of the flue will help reduce creosote build up there. If you are considering a perlite or vermiculite fill, then you are totally covered. I'd be comfortable using 304 with an EPA stove unless burning more corrosive fuel like coal. Then I'd go with 316Ti.

 

[branchburner]

A good masonry supply store will carry 4 cu ft bags of perlite for $12-15. It is different from the garden-supply stuff. I have heard it is better than vermiculite because it has lower absorbency (= zero?) should it get wet.

Make sure your tile flue is sound. An insulated liner is often a safety feature for a less-than-perfect flue, but when you loose-fill to insulate you are likely to have some variation in how much insulation is around the liner at different points. In some spots, if the liner shifts while you're filling, it may end up against the tile (especially in a 7" flue) meaning it is essentially uninsulated in those spots. I don't see that as an issue (though some do) except in cases where the insulation is essential for safety.

I made a plug around the base of my liner, above the block-off area, with a few inches each of rock-wool and perlite/cement mix (sort of a DIY Thermix). Then I poured the loose perlite in on top of that. This is one option, but I would imagine it is "unapproved". So if you go this route, be sure your building inspector / insurance agent approves! (Technically, I believe every UL liner will have it's own listing of approved insulation methods, so anything not specifically listed is not an approved application - according to at least one post on this site.)

But it is essential that the lower block-off is really sealed, however you do it - even a tiny crack and the perlite can sift through it. Aside from costing much less than Thermix, loose perlite will come out more easily if you want to revert to the original flue. But you don't want it coming out uninvited onto your hearth.

 

[staceyneil]

How can we be certain that the flue tiles are sound? They look fine but.... any way to test?

Do you guys clean your own chimneys? I am guessing you do. I assume we should have the chimney cleaned well before we install the liner. Is that something we can easily DIY, do you think? It's only 15 feet of chimney. OTOH, maybe we should hire someone to do it and check the flue tiles at the same time... what do you think?

Thanks so much for your help!

Stacey

 

[btuser]

The hardest part is getting to the top of the chimney. If you can do that without falling then you can do the rest. I think 316ti has a higher temperature rating than 304 SS. Also, insulating the chimney will give you additional protection should you get a fire. I would be inclined to skip it for an interior re-line, and if you're planning on using pour-in that can be done later if it keeps you up at night. I used the blanket and it was a pain, and expensive but I've got an exterior chimney so I wanted it surrounded.

Look for cracks in the mortar/clay. Tie a flashlight onto a string and lower it down. Big cracks bad, small/hairline cracks ok. You're really looking for shift in the masonary and entire sections that have disintergrated and fallen. Check the cleanout. I opened a cleanout once to find it full of bricks, then I removed the smoke pipe from the boiler to see it 1/2 blocked as well.

 

[branchburner]

The chimney should be swept before lining, so if you hire a sweep he can inspect the flue. You may also want to check with your building inspector and insurance agent, if you haven't already.
https://www.hearth.com/econtent/index.php/forums/viewthread/59533/

The option I would choose, assuming a tightly sealed blockoff, is simply to line without insulation (or just insulate the top). If the stove does not perform well, you can add on later.

Be sure 15' of liner is really enough - you don't want to be caught a few inches short.

 

[staceyneil]

Thank you. That is good advice!

 

[oconnor]

Stacey,

You've gotten some good advice above, but I am going to dissagree on a specific point - you likely do technically need to insulate your liner from top to bottom.

In your 1956 home, I doubt your flue would have the required 1" air gap from combustibles all around it (exterior masonary to combustibles) that is required to meet current codes. This gap prohibits dangerous heat transfer to adjacent combustibles during a chimney fire. Many liners are listed as zero/zero clearance installs when used with the correct insulations - these will always be your best choice. Zero/zero refers to zero inches from liner to masonary inside, plus zero inches from masonary to combustibles on the outside of the chimney structure.

You need to select a liner that will allow you to insulate it using the method you prefer - that means read the liner's instructions before you buy. Some liners aren't tested for use with insulation - don't buy them unless the instructions state what to use to insulate and how to apply it, as well as what the clearances to combustibles are after insulation. Simpson and Selkirk are two brands of many that meet zero/zero specs when installed with insulation, and the instructions are very clear on what to use and how to do it. Many others are not.

Additionally, in your climate, like mine here in NS, you can get enough heat radiating from the chimney to melt snow on the roof in the winter, which can re-freeze and cause some ice damming. This happened to me when I had my uninsulated liner installed, and went away after I had my liner insulated. Insulating the liner keeps the temp of the masonary down, so less heat enters the attic, and you get less snow melt.

Insulating your liner will likely cost an extra 300-500 dollars, but you will go to sleep each night knowing that your install meets all codes and is done right. That was worth it for me.

 

[ikessky]

I got my perlite from http://www.hometownperlite.com

Just like was stated previously, if you go with a loose fill perlite, make sure you have a good, sound block off. The masonry fill that I purchased was very light and will find it's way through any openings you have.

If you have a 7x10.5" chimney, you could always opt for an ovalized liner.

I think if it were me, I would have a chimney sweep out and have him clean and inspect your flue before you decide to reline. I have a FlexKing liner inside the clay tiles of my interior chimney and burned that way for two years. I finally decided to go with the loose fill perlite for a couple reasons. First, although it's not going to fill every space evenly around my liner (because I'm sure it's touching the tiles in a few places), it will work it's way around the liner and certainly isn't going to hurt anything. Second, it was fairly cheap. I over bought and still have a full bag sitting here unopened and it cost me under $75 for my chimney which is only like 18'-20'.

 

[staceyneil]

You guys have been great... thanks so much for your input. Can you double check our plan?

We have a sweep coming tomorrow to clean and inspect the chimney for us, and I'm about to order the materials. Unless you see any errors here, here's the plan:
1) HomeSaver ultra Pro316Ti 6" liner, 15' kit
2) We will fabricate a block-off plate of sheet metal.
3) Insulation: Will the block-off plate (either with or without blanket insulation on top of it) be tight enough to be able to pour vermiculite in without it finding it's way through or will it sift though and be a mess? My husband is worried about that and considering just insulating the top of the chimney instead. I'll ask the sweep tomorrow, too....

Thanks again!!

 

[ikessky]

I guess it depends on how tight your block off plate is made. Personally, I would feel better throwing some blanket insulation on top of the block off. Either way, while one of you is pouring the insulation in, have the other person watch around the block off plate to see if there is a breach. Better to fix it right away. Also, while you are pouring, remember to wiggle the liner around to help the insulation fill in the gaps and air voids.

 

[pen]

Make sure that 15 feet is enough. If that leaves you w/ extra, then you've got a very short chimney which may or may not be long enough for your stove.

I would seal the bottom well then pour the vermiculite down. W/ insulation stuffed around that liner, some sort of metal plate used, and some high temp rtv, that vermiculite should have a hard time coming through.

Next, fill it almost to the top w/ vermiculite (shaking the liner the whole while to make sure it settles) but leave room to insulate around the very top w/ rock wool insulation. That way, if the vermiculite settles you'll still have an insulation barrier at the top to keep the heat in that section.

Definately pick the sweeps brain.

pen

 

[vvvv]

liner & or insulated makes better draft. too good a draft & stove overfires! coast is windy? wind makes for better draft, normally

 

[laynes69]

I used grade 5 vermiculite I think. It looked like rocks and was very coarse. I used 24 cu.ft. on our chimney. I did it because it was cheap, and I didn't have room for a blanket. I filled ours to the top of the chimney and then capped the top with stainless. For the snout that entered the thimble, it was wrapped in ceramic fiber to keep the snout hot and keep vermiculite from entering the basement. We have a 32' chimney, and I think there is very little heat loss from the bottom to top.

 

[Northeaster1]

I have purchased the starter kit and 40' of solid (selkirk) Super-Pro Versa-liner. I had considered pouring in something like perlite or vermiculite.
However, the instructions state not to use any pour-in loose or cemented type materials. It says to use a blanket type liner.

Although it may be safe to use pour in, I figured it may cause a problem when getting inspected for insurance (WETT inspection is big in Canada)

 

[oconnor]

I have purchased the starter kit and 40' of solid (selkirk) Super-Pro Versa-liner. I had considered pouring in something like perlite or vermiculite.
However, the instructions state not to use any pour-in loose or cemented type materials. It says to use a blanket type liner.

Although it may be safe to use pour in, I figured it may cause a problem when getting inspected for insurance (WETT inspection is big in Canada)

Bottom line is that the only approved way to insulate a liner is the way the instructions say to. Any other way may not cut it when an insurance company or building inspector is involved.