Supervent chimney question

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jbrown9709

Member
Jan 24, 2009
9
NW Oregon
Hi,

I'm planning my install of an Alderlea t5 stove and have a question about the chimney install. I'm planning to use Selkirk Supervent. My house has a 3.5/12 vaulted ceiling then an attic then a 7/12 roof (scissor truss) I understand that I'll be using the cathedral box to install, and it will be framed into the bottom chords of the trusses, but being an install not envisioned in the manual, I'm not sure whether to place the attic insulation shield inside the cathedral box, or somehow (and keep it listed) close the top of the box in the attic and place the attic insulation shield on top of that. The goal is obviously to keep insulation or other debris away from the chimney pipe, but the instructions don't explicitly address this install. One video I saw using Supervent into a scissor truss, the owner extended the uphill edge of the cathedral box with hardibacker. Thanks in advance for your advice!
 

ZitRemedy

Member
Feb 29, 2016
10
Canada
Hi, just curious as to what you did here? I'm in exact situation. From what I have been reading, this is what I've determined:

1. I can insulate the support box around the chimney as long as I use Selkirk's insulation product.
2. If I want to prevent insulation or other debris from entering the support box I can just use a regular storm collar over the top.
 

ZitRemedy

Member
Feb 29, 2016
10
Canada
There should be an insulation shield to keep insulation out.

There is...in this application its the black support box that comes with the cathedral kit. If you had blown in insulation it would be blown in around the support box. You can attach a normal storm collar like the one on the chimney above the support box if you want to prevent anything from falling in or an animal nesting.

As for the insulation comment I made...Selkirk makes a universal bat insulation that wraps around your chimney section that's located in the support box to prevent any cold air infiltration.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,101
central pa
There is...in this application its the black support box that comes with the cathedral kit. If you had blown in insulation it would be blown in around the support box. You can attach a normal storm collar like the one on the chimney above the support box if you want to prevent anything from falling in or an animal nesting.

As for the insulation comment I made...Selkirk makes a universal bat insulation that wraps around your chimney section that's located in the support box to prevent any cold air infiltration.
You can only use a normal storm collar if your box is round. If it's square you need something made to fit it
 

ZitRemedy

Member
Feb 29, 2016
10
Canada
You can only use a normal storm collar if your box is round. If it's square you need something made to fit it
I've been told that its not required for Wett Inspection...as long as the support box is higher than the insulation around it. A local installer told me they use regular storm collar and it fits down over the square box....they don't usually install them unless asked by customer. I checked locally and can't seem to find a square one.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,101
central pa
I've been told that its not required for Wett Inspection...as long as the support box is higher than the insulation around it. A local installer told me they use regular storm collar and it fits down over the square box....they don't usually install them unless asked by customer. I checked locally and can't seem to find a square one.
If you can't find a square one get the insulation shield. Only a few companies make the square storm collars. The majority of what I find in support boxes when I inspect is mouse nests or nuts from squirrels etc. And they will go right through the gaps between a round storm and square box.

I know some manufacturers do not require the box to be covered but as someone who inspects lots of existing systems I can tell you that is a bad idea
 

begreen

Mooderator
Staff member
Nov 18, 2005
96,219
South Puget Sound, WA
At some point during its life, there will likely be debris falling into the insulation shield unless it is covered. If the roof is replaced it's almost guaranteed.
 

ZitRemedy

Member
Feb 29, 2016
10
Canada
If you can't find a square one get the insulation shield. Only a few companies make the square storm collars. The majority of what I find in support boxes when I inspect is mouse nests or nuts from squirrels etc. And they will go right through the gaps between a round storm and square box.

I know some manufacturers do not require the box to be covered but as someone who inspects lots of existing systems I can tell you that is a bad idea
I’ll have a look for a square one and get one fabricated if I can’t find it. I can’t use the insulation shield as I have the cathedral ceiling kit. I have scissor trusses, so my ceiling inside is like 3 or 4 /12 and my roof is 8/12. The trusses have some space between ceiling and roof for insulation. In this case I believe the support box that comes with the kit will be my insulation shield and I’ll get it covered one way or the other. That is unless someone knows how the insulation shield fits into the support box somehow…however I can’t see what this would accomplish. Maybe a call to Selkirk tomorrow.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
30,101
central pa
I’ll have a look for a square one and get one fabricated if I can’t find it. I can’t use the insulation shield as I have the cathedral ceiling kit. I have scissor trusses, so my ceiling inside is like 3 or 4 /12 and my roof is 8/12. The trusses have some space between ceiling and roof for insulation. In this case I believe the support box that comes with the kit will be my insulation shield and I’ll get it covered one way or the other. That is unless someone knows how the insulation shield fits into the support box somehow…however I can’t see what this would accomplish. Maybe a call to Selkirk tomorrow.
Just extend the support box all the way up to the roof. Then the flashing and storm collar will cover it
 
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