Class A chimney through Cathedral roof

[ethang680]

Hello all. I'm installing a 6" class A Selkirk Metalbestos/Ultra Temp chimney though a 3-4 slope cathedral roof using the roof support kit (6T-RSP 206420 ).
My question is about how to handle the plastic rafter vents that run up the length of the bays to prevent condensation buildup.
Currently I have them cut back 16" plus from the pipe center and blocked the insulation top and bottom with fabed sheet metal.
However , I cut recesses in the top of the sheet metal baffles and metal taped to seal to the plastic baffles to allow air to still rise up the roof sheeting.
Now Im wondering if this was a good idea as there will certainly be warm/ hot air coming off the pipe and going up the rafter vent to the ridge vent.
Any idea if this is a problem? Too much heat on the upper section plastic, premature localized snow and ice melt ?

I appreciate any suggestions / guidance .

Thanks , Ethan

 

[Whitenuckler]

Hello all. I'm installing a 6" class A Selkirk Metalbestos/Ultra Temp chimney though a 3-4 slope cathedral roof using the roof support kit (6T-RSP 206420 ).
My question is about how to handle the plastic rafter vents that run up the length of the bays to prevent condensation buildup.
Currently I have them cut back 16" plus from the pipe center and blocked the insulation top and bottom with fabed sheet metal.
However , I cut recesses in the top of the sheet metal baffles and metal taped to seal to the plastic baffles to allow air to still rise up the roof sheeting.
Now Im wondering if this was a good idea as there will certainly be warm/ hot air coming off the pipe and going up the rafter vent to the ridge vent.
Any idea if this is a problem? Too much heat on the upper section plastic, premature localized snow and ice melt ?

I appreciate any suggestions / guidance .

Thanks , Ethan

I'm not a builder, but I don't think you want inside hot air to go into the cavity next to your sheathing (if I understand correctly).
They should now be close off, if the ceiling box has closed off those runs. (I think).The top one would be vented to the ridge vent, and the bottom one to the soffit. Good question for a builder.

 

[ethang680]

Thanks for the info. Just to be clear- I am not using a ceiling box but a roof support kit which clamps on the Insulated pipe and mounts to the top sheeting of the roof. The pipe is exposed as it goes through the 2x10 rafters, the area is "sealed off" from the interior by high temp insulations and a trim ring. So the pipe heat will go up through the flashing on top of the roof and partially up through the rafter vent if I leave that exposed/open. Just not sure if I need to close off the rafter vent to the ridge vent or leave it open.

Thanks

 

[Whitenuckler]

Thanks for the info. Just to be clear- I am not using a ceiling box but a roof support kit which clamps on the Insulated pipe and mounts to the top sheeting of the roof. The pipe is exposed as it goes through the 2x10 rafters, the area is "sealed off" from the interior by high temp insulations and a trim ring. So the pipe heat will go up through the flashing on top of the roof and partially up through the rafter vent if I leave that exposed/open. Just not sure if I need to close off the rafter vent to the ridge vent or leave it open.

Thanks

Ya, had had some sort of different picture of the finished ceiling. I still can't quite picture it to be honest.

 

[ethang680]

This is the roof support bracket and below is where it passes through the rafters ( roof not cut yet)
You can see the opening at the top of the insulation baffle that would allow the hot air radiating from the chimney pipe to go up the bay and melt the snow and ice in that at one area.

Thanks

 

[Burnin Since 1989]

This is the roof support bracket and below is where it passes through the rafters ( roof not cut yet)
You can see the opening at the top of the insulation baffle that would allow the hot air radiating from the chimney pipe to go up the bay and melt the snow and ice in that at one area.

Thanks
View attachment 342283View attachment 342284

Hi, Have you verified that installing the chimney pipe in the manner with the roof support and not a ceiling box, meets code requirements in your area? They want a ceiling support box here.

Here is what I'm referring to. https://www.northlineexpress.com/pr...box-6dt-cs11-2?_pos=2&_psq=ceili&_ss=e&_v=1.0

Not an endorsement of the exact product or the company website selling it.

 

[Whitenuckler]

This is the roof support bracket and below is where it passes through the rafters ( roof not cut yet)
You can see the opening at the top of the insulation baffle that would allow the hot air radiating from the chimney pipe to go up the bay and melt the snow and ice in that at one area.

Thanks
View attachment 342283View attachment 342284

re hot air from house or vent pipe box - the idea is to keep the surface of the roof the same as the outdoor temperature. That is why the ceiling is insulated, and the remaining gap vented to out door air. A good roof will have a nice covering of snow, with no melting. A poor house will have ice dams backing up and then leak in the spring when it rains.

 

[ethang680]

Hi, Have you verified that installing the chimney pipe in the manner with the roof support and not a ceiling box, meets code requirements in your area? They want a ceiling support box here.

Here is what I'm referring to. https://www.northlineexpress.com/pr...box-6dt-cs11-2?_pos=2&_psq=ceili&_ss=e&_v=1.0

Not an endorsement of the exact product or the company website selling it.

Thank you , I originally thought I would use a box similar to what you are showing but when I spoke to Selkirk they recommended to roof support unit.

 

[ethang680]

Whitenuckler , Thanks . I do agree with you which is why I'm concerned. I had a continuous rafter vent from soffit to ridge that I just cut open in the area of the chimney pentation. But your reminder of the purpose of the vent made me realize I probably want to block off the vents above and below the pipe. No more air flow but no warm air either.