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I did a lot of research on air flow and insulation at the beginning of this project, but I started to get into a flow and got a bit creative with foam-board sealed ridge air pocket.

My basic design is that the area behind the knee wall is sealed and insulated from the living spaces with baffling starting from knee wall up the rafters to an air pocket along the ridge (pocket lies between roof ridge and ceiling finish) 4 roof vents (approx 4 feet below ridge) allow outflow of air and soffits will allow inflow.

The plan is to staple r13 fiberglass over baffles. Create ridge barrier with 1 inch foam board with foil on two sides (see pics) and seal any gaps and cracks with spray foam.

My question lies with the foam-board ridge air pocket. Its feasible to do, but is it the best option?

The images below are captioned, let me know if more description or photos are needed for clarification.

R13 insulation over baffle on left. Baffles terminating at foam board below roof vent at center. Baffles exposed on the right.:

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Another angle:

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Another angle with exposed roof on the right:

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These channels exist throughout, which is why I have to create air tight seal around baffling using spray foam and foam board:

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  • Looks basically good. The devil is in the details.
    – Hot Licks
    Mar 21, 2022 at 22:11
  • The details are what keep me thinking at night... what have I not thought of yet.. what little crack is waiting to be filled..
    – timz08
    Mar 22, 2022 at 0:07
  • Why are you adding the blue board over the yellow channels? That's simply creating 3 additional air channels on this side of the yellow for air to flow and reducing the room for the fiberglass insulation. Maybe I'm missing something...
    – FreeMan
    Mar 22, 2022 at 12:18
  • The blueboard only goes at the top under the ridgeline because the yellow channels need somewhere to flow into that will open up to an exit/vent.
    – timz08
    Mar 25, 2022 at 18:40

1 Answer 1

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The Code says you need to provide 1” air space between the insulation and the bottom of the wood (roof sheathing).

It appears that you have that clearance in most areas. Areas where the “C” channel touches the wood , it would block the flow of air.

Does that triangle area at the top have a place for the air (from the 1” air space) have a place to escape?

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  • Yes, there is a 2" high by 4" or so wide triangle that follows through all of the studs allowing air flow from all rafter gaps to the roof vents
    – timz08
    Mar 22, 2022 at 2:53

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