liner insulation necessary?

[chrismalloy]

Hi,
First of all let me apologize for asking this question which most certainly has been answered already somewhere on this site. I searched for about 30 minutes but couldn't find my answer, so I'm creating a new post here.

I just purchased an Osburn 2400 insert for our home. The chimney is 14 feet from top to bottom. In addition to the $500 stainless steel liner, the salesman is trying to sell me a $400 insulation kit for the chimney liner ($300 for the material and $100 for the install). Do I really need the insulation kit, which basically consists of a roll of insulation and some tape (although I'm sure it's fire rated, etc.)? Thanks for all the great advice on this site!

 

[woodzilla]

I think you'll find most people here will recommend insulating an external chimney liner. A chimney located within the home is not in need of insulation. I do know some wood burners that wish they had insulated.

 

[chrismalloy]

Thanks for your reply. I forgot to mention that my chimney is centrally located in my home (if that makes a difference).

 

[woodzilla]

you should have no problem without it then.

 

[oconnor]

you should have no problem without it then.

I'm not sure how you can come to that conclusion based on chimney location. As I see it the issue around liner insulation is twofold:

1: draft quantity - perhaps this is where the location conclusion comes in
2: building code compliance - this is where your chimney construction and airspace comes in.

Each liner is tested to meet fire safety requirements under different conditions (UL 1777 specification). Check the detailed instructions for the liner (not always obvious, see my other post today re liners) to determine when insulation is required, and how much is required, then check that against the flu you are installing it in. Each liner can be different, based on the conditions the manufacturer asked to have it tested under. Some need more insulation than other to comply with the tested conditions.

Mine is a chimney located in the center of my house, and did not require insulation to maintain a proper draft condition. It does however need insulation to be safe: I have no existing clay liner in the flu, and no constant air clearance around the outside of the brick chimney. (i.e. 2 x 4's in contact with brick as part of the construction of the flu and house). I have a zero clearance compliance problem, as do many others, maybe some of you reading this do too, and don't even know it.

I need an insulated liner to be safe, to meet safety codes, and to keep my insurance coverage valid. (Just like making sure you have an approved stove, it is only "approved" if it is installed under "approved" conditions).

See my post from earlier today for the rest of the details on my problem:

https://www.hearth.com/econtent/index.php/forums/viewthread/23980/#257300

Hope this helps

 

[BrotherBart]

Exactly right Brent. Glad you got here first. Saved me a lot of typing.

 

[woodzilla]

I was reciting what I had read in forums previously. However partial an answer it may have been on local codes, I still say a central chimney drafts better.

 

[oconnor]

No disagreement here on that point Woodzilla. I'm just very surprized by the lack of knowledge, even in the installer world, about the liner insulation question. Keep in mind too, that it isn't a local code variation question that requires insulation of a given liner in certain situations, but national safety specs, both in Canada and the US.

 

[ba_jie]

My chimney is located inside the sunroom which is adjacent to the family room. The sun room is not insulated at all.
So should i consider my chimney as internal one or external one?

 

[oconnor]

The question is more about how much of the flue is exposed to colder weather, therefore cools quicker. If it is inside an attic, and not exposed to the elements, less cooling.

JIE, is yours a masonry chimney? I'm trying to picture it...

 

[ba_jie]

It is a masonry chimney. I think the orignal home owner build a sun room adjacent to the family room(one level only). So the chimney is inside the sun room now.
However, 9 ft of the 20 ft chimney is above the roof, plus the sun room has no insulation at all. So i would think my chimney is an external one.

Anyhow, i probably won't bother with liner insulation now. My hands are already full of work and code weather is around corner...

The question is more about how much of the flue is exposed to colder weather, therefore cools quicker. If it is inside an attic, and not exposed to the elements, less cooling.

JIE, is yours a masonry chimney? I'm trying to picture it...

 

[acesneights1]

I just went through this with Chimney liner depot. They said I probably didn't need one because I have a central chimney and it's masonry with clay liner in very good condition.

 

[theheatelement]

Most chimney liner companies will not require insulation kits... that is something done after installation especially with liners that are 304 ours are 316ti.. If you have any questions feel free to pm me...

 

[oconnor]

Insulating the liner is not about what the liner company requires, but about what is required to meet code. Unless your chimney has the code required airspace around the outside of the brick chimney, then you probably need a liner to meet code. Some liners are insulated after install with Perlite or vermiculite or other materials, but many are insulated before install with a ceramic wool wrap.

Even if you have clay liners, you may still need to insulate, particularly if you chimney was originally built for an oil/gas appliance and is now going to vent a wood fired appliance. This is because the construction requirements for these two flues are different, because the temperatures are different ( a wood flue can regularly reach 1200F flue gas temp, and an oil flue will never experience that heat)

In the end, the National Fireplace Institute and the Chimney Saftey Institute of America both recommend you "Insulate Liners Except in Special Circumstances" Anyone who says you don't need to, and can't articulate the special circumstance is not following the recommended best practices of these two national bodies.

The type of steel doesn't have anything to do with whether you need to insulate - how a given liner was installed during the test process to achieve the UL1777 rating is what determines the need to insulate.

Many manufacturers do not post the instructions for how to install their liners on thier websites, and therefore many consumers never find out about the insulation requirements before thet get the liner home, but I have had this chat with MagnaFlex before.

I'm looking forward to the day when more manufacturers follow the lead of Simpson and Selkirk ( and other too I'm sure, but these two stand out in my mind) and post detailed instructions, including specs on when insulation is or isn't required, and when they recommend it, right on their websites.

Read thru the Best Practices pamphlet by following the link in my signature.

And by the way, I am not affiliated with any company of organisation associated with the selling or promoting of wood heat products or services.

 

[sbender61]

That is a very good point about having chimney liner installation steps on the company site. It would save people a lot of time and frustration.