Exterior chimney, insulated liner needed?

[briv]

I decided to pick up my insert and perform the installation myself. The 6" SS liner was purchased at the same time as the stove but they did not include insulation (didn't raise any flags since I knew nothing about it at the time). Upon further research I found multiple threads with different insulating techniques. I placed a call with the dealer and they said insulating the liner probably isn't necessary. I called another dealer (closer to my house) to see if they had any in stock, he asked why I was insulating and said that 70% of his installs are NOT insulated.

A few points to note: My flue is lined with terracota (sp?) tile that appears solid within the top couple of feet. My chimney was swept and he did a quick inspection but did not get into the nuts and bolts of the entire flue (mainly just ran the brush and looked at the outside of the masonry and the top few feet). I would go with a 1/2" wrap insulation if I was to insulate.

So, my question to you all knowing hearth.com members, is insulation needed on an exterior chimney? What benefits does it provide that I will not get from an uninsullated liner?

 

[RedGuy]

Well to keep the UL listing on your liner you'll need to insulate it. My insurance provider requires a UL installation as I'm sure many would, so in that instance yes insulation is required. From what I understand it will also greatly reduce cresote build up as the liner will remain hot all the way to the top. For me the safety factor is worth the extra cost of insulating.

 

[begreen]

It is required unless the chimney meets code (few do). Insulation can also help stove performance. How tall will the liner be?

 

[Scotty0844]

A friend of mine works for a stove dealer. I asked him this same question when I installed my liner. He said for exterior chimneys it is a good idea because it takes so much longer to get the temps in the chimney up. My chimney is in the center of my house so I didn't insulate it and I have no draft or creosote problems. I do think if my chimney was exterior I would have gone with the insulation though.

 

[branchburner]

If you decide not to insulate the full liner, you might want an insulated blockoff plate to reduce heat loss.

 

[granpajohn]

The advantage is better draft. Unless your chimney will be taller than most, you may want to do it. I had the same thoughts, and in hindsight, I am very glad I opted to put on the insulation.
Second....I found wrapping with insulation to be not much more work at the time. To do it after the fact would be a big headache.
Last...you don't have to wrap every square inch of the liner to get pretty good results. For me the hardest part of the whole job was de-ovalizing the liner at the hook-up to the insert. But that's a different story.

Oh, on the code. When I checked this out (a few years back) I found that a terracotta lined brick chimney, (in good condition), does not require the insulation.
Do it....It beats having regrets later.

 

[vector1701]

I decided to pick up my insert and perform the installation myself. The 6" SS liner was purchased at the same time as the stove but they did not include insulation (didn't raise any flags since I knew nothing about it at the time). Upon further research I found multiple threads with different insulating techniques. I placed a call with the dealer and they said insulating the liner probably isn't necessary. I called another dealer (closer to my house) to see if they had any in stock, he asked why I was insulating and said that 70% of his installs are NOT insulated.

A few points to note: My flue is lined with terracota (sp?) tile that appears solid within the top couple of feet. My chimney was swept and he did a quick inspection but did not get into the nuts and bolts of the entire flue (mainly just ran the brush and looked at the outside of the masonry and the top few feet). I would go with a 1/2" wrap insulation if I was to insulate.

So, my question to you all knowing hearth.com members, is insulation needed on an exterior chimney? What benefits does it provide that I will not get from an uninsullated liner?

I have had the same question as I am looking to buy my first wood insert and I talk to dealers and installers around here (Rhode Island/Mass/CT) NONE of them insulate the liner and even react in a "your wasting your money" way after I ask the question. Common answer is to block plate or insulate around the bottom and then again at the top. Common reasoning is that if this was a much colder climate they would consider it. I am 50-50 on whether to get the liner insulated or not....

 

[begreen]

How many of these dealers are aware of code and have their work inspected? I would be wary of a salesman for this kind of question.

 

[dave11]

I have a basement stove with a nearly 30 foot run to the top of the exterior chimney. 6 inch liner uninsulated, because there was zero clearance left for insulation. As far as I can tell, the stove doesn't suffer for it, and I have a good quality draft meter which measures well within the recommendation for my stove, despite two 90 degree bends.

So I think its hard to say ahead of time if insulating the liner is necessary, though if it can be done easily, I don't see a downside other than cost.

The problem is that few, if any, have compared the draft of an insulated versus uninsulated liner in their own setup. Folks usually stay with what they have.

 

[granpajohn]

Although I still recommend the insulation,(speaking from experience), the salesman is correct about it not being required. Best explained here:

http://www.chimneysweeponline.com/ffwrapwhen.htm

Highlights:

Forever Flex Top Sealer Plates seal so tightly, they virtually prevent the flow of air up the flue around the outside of the liner. This creates "dead air insulation" around the liner, and in most installations in code-approved chimneys, no further insulation is needed. There are some instances, however, when additional insulation is recommended or even required.

A) Safety Code Requirements
The Code Spec for chimney liners is UL 1777. To maintain its listing to the UL 1777 Standard, additional insulation must be added to your Forever Flex Liner installation if any of these four things are true:
1) You are venting through an air-cooled metal chimney (the type used for manufactured zero-clearance fireplaces).
2) Your existing masonry chimney is unlined, partially lined, or has a liner with open cracks in it.
3) A 1" airspace has not been maintained between the existing masonry liner and the outer chimney structure.
4) A 1" airspace has not been maintained between the outer masonry chimney structure and surrounding combustibles.

BTW....The ChimneySweepOnline site is a great place to learn. Mr. Tom Oyen will usually (sincerely) answer email questions too, if you really get stuck.

 

[begreen]

Unless the salesman is knowledgeable about chimneys and came on site for a detailed inspection, he has little idea sitting at his desk about the chimney. Tom's post says it pretty clearly:

A) Safety Code Requirements
The Code Spec for chimney liners is UL 1777. To maintain its listing to the UL 1777 Standard, additional insulation must be added to your Forever Flex Liner installation if any of these four things are true:

1) You are venting through an air-cooled metal chimney (the type used for manufactured zero-clearance fireplaces).
2) Your existing masonry chimney is unlined, partially lined, or has a liner with open cracks in it.
3) A 1” airspace has not been maintained between the existing masonry liner and the outer chimney structure.
4) A 1” airspace has not been maintained between the outer masonry chimney structure and surrounding combustibles.

This doc may also be helpful when deciding on whether to insulate a liner:
http://www.woodheat.org/chimneys/bplinerusers.pdf

 

[branchburner]

Two other common errors in masonry chimneys, that can lead to cracked tiles, are:
1) failure to use refractory mortar at the tile seams
2) failure to leave expansion room between the crown and top tile

Taking these along with with BG's two airspace issues, a mason I just talked with says he knows of very few other masons who actually build chimneys to code, even on high-end jobs.

 

[cmonSTART]

BG and branchburner are correct. Insulate the liner. It will stay cleaner and perform better with your chimney too. It's pretty easy to do, also.

 

[vector1701]

I appreciate the valuable information. I will need to check out pricing from installers as an insulated liner may cost 300-500 more in total install cost (which I would be willing to pay as long as it is done right). Outside of the DIY homeowner, not many installers I have talked to install or have installed insulated liners.....and I don't plan on getting 30 feet up in the air, gravity is not my friend.....

 

[begreen]

Will the liner be 30'? If there aren't a lot of elbows on the interior, this might be a candidate for downsizing the liner which could balance out the cost of the insulation.

 

[vector1701]

I would estimate between 25 & 30 as the chimney extends about 5 feet above the roofline, the only elbow would be at the bottom. See attached. Since the stove has a 6 inch exhaust what would you downsize the liner to?

Thanks

 

[begreen]

What stove? Can you add this to your signature line?

 

[vector1701]

I was looking at the Vermont Castings Merrimack, but yesterday bit the bullet on the Jotul 550 Rockland. Hopefully, we can get it installed in a few weeks. Bought it at Preston Trading Post in Connecticut. I again asked about insulating the liner and the salespeople said the installer makes the call if the liner needs insulation depending on the condition of the flue. They probably will not insulate it as they pack the bottom and top of insulation to hold the liner and to create an air gap. I then got the line "air is the best insulation you can get and once it is packed at the top and bottom, you should be fine and draft is not an issue." I then wondered if the chimney was in that bad shape, would the installer just happen to have 25-30 feet of insulation in his truck? I would think not....doesn't sound like many people/installers insulate the liner in this area (CT/RI/Mass) at all...

Your input on this is greatly appreciated....what a great forum

 

[raybonz]

I was told by my installer that all that was required since I had a clay (damaged with vertical cracks by a chimney fire) that I did not require insulation after cleaning.. Well I checked here and even though I have an interior chimney I told them to knock out the clay liner (inside dimension 7x7") and insulate the liner to meet UL1777.. Fortunately my insurance covered the expense and now I have the best draft in over 20 yrs..

Ray