Cathedral ceiling install

From the SuperVent SuperPro installation manual:

NOTE: To reduce cold air infiltration into the dwelling you
can install the optional Universal Shielding Insulation (JUSI)
into the Cathedral Support Box. See separate installation
instructions packaged with the JUSI.

Click to expand...

I'm trying to get parts together for a chimney install as well. Good luck!

Mine still looks like this:


I really need to get up there and seal it off. I used a lot of barn tin inside, so I think I will insulate the opening, then build a barn tin chase around the flue pipe.
Barn tin:

I asked the same question! So instead of insulation im just gonna try and seal any air leaks. I used high temp silicone to seal the seams in the support box, also stuck it in between the ends that dont meet on the brace around the class a which supports it in the box. Ill play some more with it but would still like a layer of some non flamable insulation!

No expert, but I've done 2 cathedral I stalls using supervent parts. Canadian winters, and i didn't use any insulation in the box. The JUSI that Holden mentioned, or possibly roxul ( might actually be the same material - rock wool) could be used. For me, if its cold, the stove is lit - this space didn't ever seem to be an issue. I'm curious to know if many people bother, or if this is allowed with other manufacturers or in other jurisdictions?

A little googling and it brings me to a thread here!
https://www.hearth.com/talk/threads/selkirk-supervent-installation-begins.75341/

Looks like the jusi has some form of insulation touching the class a chimney

Mine is too shallow to use the jusi but i wonder if i could stuff that insulation inbetween the box and the class a.

According to the supervent parts catalogue you can use this insulation in an attic insulation shield, wall thimble, or cath ceiling support box, to stop air infiltration.

Motor7 said:

Mine still looks like this:

I really need to get up there and seal it off. I used a lot of barn tin inside, so I think I will insulate the opening, then build a barn tin chase around the flue pipe.
Barn tin:

Click to expand...

Hello,

Just wondering how much torque you put on the ring clamp thats holding your pipe centred? I'm thinking it should be kept just snug only so the pipe can expand. I recently tightened mine up, but I may have over done it, as my stove now pings like crazy on heat up.

begreen said:

This is a grey area. If you want to be squeaky right, get the mfg. insulation and keep the receipt. That way you are documented with an approved insulation. It's probably just roxul, but it is best not to have any area of dispute with the insurance co or inspecting authority.

Click to expand...

It looks and feels just like fiberglass. It resembles roxul in no way. We have lots of both, rarely use the JUSI.

I did an 8" chimney through a cathedral ceiling in Dec. and fretted about heat loss. The reality for me is that my stove is on 24/7 from cold weather until warm so even though there may be slight heat loss, it's minimal. I used the proper mfg's ceiling kit and made sure that everything was as air tight as possible. Remember, most people who have high cathedral ceilings also have a lot of windows and even the best windows on the market are horrible for insulation value compared to your walls. As long as there's no major air leakage, the connection will be have a very minimal effect on your total heat loss. The attached shows our stove during construction of the pipe after the ceiling adapter was in place. I wanted the stove dead center between the windows so I was forced to use two 30 deg elbows to get the ceiling support to fit exactly alongside the center beam. Not fun. Ceiling is 16.5' off floor.

I don't really think the insulation is intended to reduce heat loss as much as prevent condensation as a result of the heat loss.