Why is it possible to OVERINSULATE a flue liner?

[fire_man]

Just trying to understand why a liner manufacturer would make a statement like this:

WARNING! Do not use any loose fill, cementious, or blanket insulation thicker than 1/4 inch equivalent refractory ceramic fiber. These products void the Saf-T Liner and may create unsafe conditions resulting in damage to the masonry chimney and/or the liner system.

 

[branchburner]

Because the liner manufacturer has only tested the product with the 1/4" blanket, so can only make safety claims for that application, and that one alone. It is a CYA statement.

 

[fire_man]

Because the liner manufacturer has only tested the product with the 1/4" blanket, so can only make safety claims for that application, and that one alone. It is a CYA statement.

Makes sense. When contacted they could provide no technical reason.

 

[branchburner]

Brent O'Conner has started several good threads on why to insulate by the liner manufacturers' specifications if you want to be to code:" In the end, the manufacturer's instructions apply."
https://www.hearth.com/talk/threads...ternal-masonry-chimneys-when-relining.123668/

If you want to deviate from the applications specified by the liner manufacturer, such deviations must be approved by an inspector to formally meet code, even though your alternate application might generally be deemed "safe."

 

[mstoelton]

Freaking Lawyers - I hate em.

Knowing this I would not buy a saf-t liner.

 

[mstoelton]

They need to start testing their liners with different insulation materials.

 

[fire_man]

The linked article on "Best practices for chimney liner installation" is well written.

 

[fire_man]

Freaking Lawyers - I hate em.

Knowing this I would not buy a saf-t liner.

Yup I think its all about the lawyer talk.

 

[Nick Mystic]

Or there could be a good reason for their warning. Since insulation on a liner is intended to keep the gasses inside the liner hot to get a better draft and less creosote build up in the flue it makes sense that it is possible to retain too much heat inside the liner. Stack temperatures can be very high during certain periods of the burn cycle and if some of that heat can't escape through the liner perhaps the liner would deteriorate quicker due to the stress. I'm just speculating, but I know members have posted photos of flex liners looking like they melted and have started to come apart, so the liners aren't bullet proof.

 

[fire_man]

I can't imagine a technical justification,especially for a rigid liner. They are saying to use 1/4" max ceramic blanket.

I think branchburner got it right, it was only tested that way. They make their own expensive "safe-t-wrap" brand of insulation "shells" that snap over the liner.

Even their warranty says "void unless saf-t-wrap" insulation is used.

 

[bholler]

I think branch burner is right. But I also think it may be to sell more of their insulation because most other insulation kits are 1/2" it would force you to buy theirs. That is only speculation I have no evidence to support it but it sounds fishy.

 

[fire_man]

Not only does it force you to buy their insulation, but it's a ridiculous expensive arrangement of snap-on shells.

 

[BrotherBart]

They probably do it for the same reason somebody always posts in bold text.

As to insulation everybody talks about loose fill and pour in insulation, but I have yet to see any liner manufacturer say they tested with it. If anybody has I would appreciate a link. One minute people say always follow manufacturer's instructions and in the next breath they talk about dumping vermiculite down the chimney.

I may be missing something.

 

[fire_man]

I would like to hear how Selkirk expects you to limit the pour-in insulation to the 1/4" max thickness rule.

 

[bholler]

I am sorry bart most manufactures test with both insulations wrap and pour. At least every set of instructions I have read says so. Some test for specific mixes and most rigid says no pour in but most flex was tested for it. And loose fill is no longer recommended by any I have seen by the way

 

[fire_man]

Selkirk's warning label says not to use greater than 1/4" equivalent to ceramic refractory fiber when using
loose fill or a cementious product . So the warning is not prohibiting pour or cement based.

I just don't understand how you could even control the thickness of pour or cementious.

Selkirk's warranty label prohibits anything except their own insulation, so there is a contradiction.

 

[bholler]

I am not sure why you would use both types of insulation seems weird to me. As far as controlling the thickness it takes experience you need to pour evenly around it and shake or vibrate the liner to evenly distribute it.

 

[branchburner]

One minute people say always follow manufacturer's instructions and in the next breath they talk about dumping vermiculite down the chimney.

Hey, I resemble that remark.

But the point is, always follow manufacturer's instructions IF you want to be strictly to code... dump vermiculite down the chimney IF you want to save money and don't care about formally following code. So it is not to push one over the other, but to provide a reason why you might choose one over the other, and to enter into that decision with more knowledge.

I made my decision to use loose perlite without ever considering it was not an approved application for my liner. That realization came after it was in. Am I going to pull it now? And clean up all that perlite that pours into my living room?? Not today.

BTW, if anyone has EVER experienced liner/chimney failure, or house fire, or denial of an insurance claim due to loose fill perlite or vermiculaite, I would love to hear about it. (I'll be sure to let you all know if it happens to me.)

 

[branchburner]

you need to pour evenly around it and shake or vibrate the liner to evenly distribute it.

Of course since loose perlite or vermiculite is granular, it is impossible to have even contact over the length of the liner. I think that's one of the reasons it's not approved.

 

[BrotherBart]

Hey I am the guy with no insulation around either liner. I am just taking issue with the idea that no insulation doesn't meet liner vendor requirements and perlite, vermiculite or Bud Light do meet the requirements.

Liner warranties are only good to use to start the first fire anyway.

 

[bholler]

well loose fill perlite or vermiculite was at one point used it is no longer acceptable to use and is not tested with any liners. The mixes of vermiculite and cement are tested with many liners and they are a ul approved chimney insulation material. They are not tested with some liners and are not allowed for others. And what makes you say liner warrantees are no good anyway?

 

[pen]

what makes you say liner warrantees are no good anyway?

To me they are nearly pointless because if I need to use the warranty, either I did something wrong that wouldn't be covered, or else they did something wrong when manufacturing and I wouldn't want another one of their liners in my chimney due to their screw up.

 

[bholler]

Ok well most that I have come across give you a check not a new liner and yeah if you don't follow directions I would not expect them to honor it.

 

[bholler]

And by the way the reason loose fill is no longer recommended is because over time it would settle and pack in at the bottom not allowing the liner to expand and contract and leaving no insulation at the top.

 

[pen]

don't forget all of the other limitations on the lifetime warranty's that come with many liners.... such as those of us who sweep our own chimney wouldn't be covered unless we hired a pro once per year.