Seeking confirmation of oval liner size

[SecondaryBurn]

Hi all, for the wood insert install that the place selling the stove will do, I'm probably going to order the oval liner myself, and I'm seeking some confirmation on a few points from the more seasoned (pun kinda intended) folks, here.

Neo 2.5 (so, 6" vent opening at the back of the stove). and a goofy rectangular clay flue that's has interior dimensions of approximately 6.25" x 10".

1. Does any places sell pre-insulated oval liners? I found some old posts where one was referenced but when visiting that store's website I couldn't find such a liner.

2. Using Rockford's chart (I couldn't get a price from Olympia because it appears to be available only to vendors), below, and their calculator, the 5" x 8.15" seems to the appropriate corresponding oval liner:

5 in. x 8.15 in. (28.22 sq. in. cross section), ovalized from 6.5 in. round liner.**

3. I'm assuming that 1" at the tightest point of the liner compared to the flue (5" wide in a 6" wide flue) and 1.85" at it's most spacious (8.15" in a 10" long flue) is enough space all around for the insulation blanket and the mesh, but I'm confused about the following description of the 1/2" vs the 1/4" insulation wrap:

Since the flue is surrounded by cement within the chimney and no part of the liner will actually be within a number of inches of combustible material, would 1/4" suffice?. I'm not sure that there'd be space in the flue for an additional 1.5" of padding around the liner.

4. Given that it's a 6.5" liner that ovalized, I would want the insulation kit for 7-8" diameter pipes, right? (the next smaller one is for 3-6" diam.)

Thanks for your help!

 

[bholler]

Since the flue is surrounded by cement within the chimney and no part of the liner will actually be within a number of inches of combustible material, would 1/4" suffice?. I'm not sure that there'd be space in the flue for an additional 1.5" of padding around the liner.

That distance they quote is from the outside of the chimney structure not from the liner at all. The 1/4" give you no reduction in the allowable clearance the 1/2" gives you zeroclearance which means wood can be touching the outside of the chimney with the 1/2" The 1/2" will also give you better performance than the 1/4"

 

[ccmac]

Your 1/2in insulation should still work just ensure the overlap of insulation is on the long side of the oval liner since you have 10in to work with on that side. It will be a bit snug for sure but barring any issues such as flue tile ajar, sloppy mortar intruding into the flue, you should be fine. as far as insulation size, you could get away with 6in since it overlaps 1/2in (on a 6i liner, it won't on a 6.5in liner) but most would opt for 7in.

 

[SecondaryBurn]

That distance they quote is from the outside of the chimney structure not from the liner at all. The 1/4" give you no reduction in the allowable clearance the 1/2" gives you zeroclearance which means wood can be touching the outside of the chimney with the 1/2" The 1/2" will also give you better performance than the 1/4"

Apologies for being a bit daft, but I'm still confused: Wood (the roof framing) already is in direct contact to the brick chimney--in which is the filled the mortar that surrounds the clay flue--where it passes through the roof joists at the base of the attic and then the rafters. Is the point that at 1/2" thick, the liner can be in contact with the sides of the flue but at 1/4" there needs to be 1" of space between the clay flue and the insulation?

 

[begreen]

1. Does any places sell pre-insulated oval liners? I found some old posts where one was referenced but when visiting that store's website I couldn't find such a liner.

DuraLiner is preinsulated and comes in oval sections, rigid or flex. It's 4 3/4" x 7 3/4".

 

[bholler]

Apologies for being a bit daft, but I'm still confused: Wood (the roof framing) already is in direct contact to the brick chimney--in which is the filled the mortar that surrounds the clay flue--where it passes through the roof joists at the base of the attic and then the rafters. Is the point that at 1/2" thick, the liner can be in contact with the sides of the flue but at 1/4" there needs to be 1" of space between the clay flue and the insulation?

No what that means is that your chimney currently does not meet code and could pose a fire risk. To correct that issue you need to use 1/2" insulation wrap.

 

[Supersurvey]

What is the final dimension with the insulation?

 

[SecondaryBurn]

No what that means is that your chimney currently does not meet code and could pose a fire risk. To correct that issue you need to use 1/2" insulation wrap.

I misspoke--I don't know if there isn't a suitable fire block between where the chimney passes through the ceiling joists and rafters, but shouldn't assume, either, I suppose.

DuraLiner is preinsulated and comes in oval sections, rigid or flex. It's 4 3/4" x 7 3/4".

Are there lenghts greater than 60", though? I looked on Northlineexpress' site and the longest they offer is 60" in length. I'd need to buy 4 and joint them together.

 

[begreen]

Duraliner is in sections that you pop-rivet together with stainless pop-rivets. It comes in flex or rigid sections.

 

[bholler]

I misspoke--I don't know if there isn't a suitable fire block between where the chimney passes through the ceiling joists and rafters, but shouldn't assume, either, I suppose.

You just said above that the wood was in contact. Is that correct?

It comes in flex or rigid sections.

Yes but the flex sections are uninsulated so they need wrapped like any other regular flex.

 

[SecondaryBurn]

You just said above that the wood was in contact. Is that correct?

Right, and then I followed up by saying I misspoke: although I've been up in the attic I haven't looked closely at how the brick chimney passes through it and the roof, and whether or not there's a suitable fireblock between the chimney and the ceiling joists or rafters. Looking at it from the roof, I see where the shingles meet the chimney, or rather the flashing around the "base", and simply assumed that either the plywood sheathing beneath it or the rafters themselves were in contact with the brick.

It seems that if there's a question about it, then 1/2" should be chosen to err on the side of caution, but 1.5" added to a liner that's 5" wide on the narrow side pushes it beyond the 6.25" interior width of flue.

 

[bholler]

Right, and then I followed up by saying I misspoke: although I've been up in the attic I haven't looked closely at how the brick chimney passes through it and the roof, and whether or not there's a suitable fireblock between the chimney and the ceiling joists or rafters.

OK I didn't get that sorry but it is not a fire block that is required, it is an air space.

 

[SecondaryBurn]

OK I didn't get that sorry but it is not a fire block that is required, it is an air space.

so literally nothing touching the exterior of the--in this case--brick chimney through the attic and roof except for the flashing?

 

[bholler]

so literally nothing touching the exterior of the--in this case--brick chimney through the attic and roof except for the flashing?

Pretty much yes. Here is the code

http://www.rumford.com/code/clearances.html