Liner Install Question

[70Cougar]

I'm planning my install and have a couple quick questions. I read a few posts on this forum and this great article on how to make a block off plate {https://www.hearth.com/talk/wiki/make-a-damper-sealing-block-off-plate/}, but I was wondering...

1. Is the Roxul to be used the Safe'N'Sound in 'bats' that can be purchased at the local big-box hardware store, like this Roxul Safe-n-Sound at Home Depot?
2. Should I stuff some Roxul insulation at the top of the chimney around the liner, below the rain-cap, as well as above the block-off plate?

 

[fire_man]

An oval liner is a pain in the butt. Insane to try to install and brush. That thing is hanging on a mortor joint and a cone will get ya past that. Sure insulated liners are nirvana but with that good condition tile lined flue pull a 5.5 down there like I did and if you want to insulate later use pour in. But if you seal off the bottom and stuff Roxul in the top under the top plate the thing will try to suck splits up the pipe like mine in the basement does. Actually the one on the first floor pulls almost as hard.

I'm trying to get a 6" insulated flex pipe down a 6.5"x11" ID clay liner which is in good shape (25 feet long, exterior chimney).
Same question: to ovalize a bigger liner with insulation or keep it 6" uninsulated round. I think BrotherBart is right, oval is a pain to clean and I think the flow restriction of oval offsets the benefit of insulating.

As long as the clay is in good shape, BB has a good point.

 

[BrotherBart]

No decision to make. A round easy to clean 5.5" inch liner or a 6" liner you destroy trying to get it down there?. And I swear that the 5.5" has higher velocity when it gets hot. Especially the night this stove went to a thousand degrees shut all the way down.

 

[fire_man]

What I don't get, why is it ok for me to draft my stove or fireplace directly into the clay liner according to the stove manufacturer and according to numerous inspected installations, but gosh forbid I decide to line my perfectly good clay liner with SS flex, the "you have to insulate" police come out.

 

[bholler]

You don't necessarily have to but it would be much better if you could. Now I realize there are some situations where there is no way to get enough insulation in there. In those cases if possible we break out the old clay to make room but that is not a home owner project. And yes good clay can work fine we work on lots of clay lined chimneys that work just fine. By the way code and stove manufacturers still say it is ok to do a direct connect with a stub of pipe through the damper but most of us agree that that isn't a good idea.

 

[fire_man]

I was hoping bholler would chime in - he sounds code oriented which is good.

In what case would I NOT have to insulate a SS liner running through an exterior chimney which already has a perfectly good clay liner?

In my case I need to get a 6" flex liner into a 6.5"x11" ID clay liner that is in perfectly good shape, it never even saw a puff of smoke against the clay.

Does my 6" SS liner HAVE TO meet UL-1777 requirements even if my clay liner would have been good enough WITHOUT the SS liner?

I'm going to contact my building inspector and my insurance co. and get their take on it.

 

[bholler]

If you have less than 1" clearance from the outside of the masonry to any combustible materials it needs to be insulated. And if that 1" is not there your existing chimney with the clay liner does not meet code either.

 

[fire_man]

How can any chimney ever meet the 1" requirement if it's measured from the outside of the masonry?
My chimney has 3 exterior sides, and one side contacts the house all the way to the top.

This is not my chimney but it's similar.

 

[bholler]

In that case it needs insulated in order to meet code and liner manufactures instructions that is the problem chimneys almost never meet that clearance requirement. And it also does not meet code now with the clay liner.

 

[fire_man]

So you are saying any masonry brick chimney that touches a wooden structure cannot have a fireplace operating into a clay liner and meet "code"?

 

[bholler]

Yes that is the code. That general lack of clearance is why we insulate any solid fuel burning liner we put in and most others as well.

 

[fire_man]

Why would any insurance company ever write a policy on any house that has a clay lined chimney?

The chimney would have to be built completely separated from the house to ever meet those requirements.

 

[bholler]

Well most houses have multiple code violations inn many different places. And you don't have to bring them up to code unless you work on that system. Now if we are called out to do a real estate inspection we will not that violation and say it does not meet modern codes. Now when a liner is put in then it needs to meet modern code and to get that zero clearance you need to insulate.

 

[bholler]

By the way those clearances are for the flue the requirements for te fire box and smoke chamber are different

 

[fire_man]

Wait a minute, you are saying the 1" clearance requirements are for the internal flue, not the exterior brick? Now I am confused.

 

[bholler]

no it is from the exterior of the masonry

 

[fire_man]

This picture helps.

1/2" of ceramic blanket provides zero clearance to combustibles. 1/4" blanket provides 1" clearance.
So if the SS liner is 1" from combustibles would 1/4" blanket be enough?

 

[bholler]

no those clearances are with nominal 4" masonry in between