HELP with insulation problem !!!

This is a repost.

Today I inspected a cathedral ceiling on an addition that wasbuilt 8 mo. ago. There is a hole in the ceiling allowing me to see up in the cavity. The roof was constructed in the following layers from the outside-in:

25 year 3 tab shingles
tar paper
5/8" plywood sheathing
1" foamboard (nailed between the joists, to the underside of sheathing
Dura vent air spacer (the styrofoam ones that help maintain the gap)
R 30 insulation w’ kraft face
3/4" T & G pine planking

My concerns are as follows:

  1. The dura vent isnt under the roof sheathing, its under the foam board. The cold airflow doesn’t run along the underside of the roof sheathing, it runs under the foamboard. Isn’t this a double vapor barrier that might catch moisture and create a slew of problems?

  2. The location of the foam board wouldnt seem to increase the “R” value since there is a stream of cold air on the under (interior) side of it.

  3. The T & G has many gaps and spaces that is allowing heat & moisture into the cavities and has caused major ice dams and leaks. Shouldnt there be a poly vapor barrier or drywall under the t & G pine planking?

Help… and thanks.


Depending on the type of styrofoam used, some do have characteristics of a vapor barrier, thus it could be considered as doubled. If I’m reading it right, the kraft face paper is your vapor barrier and would not require additional plastic under the t&g ceiling.

Thanks for helping out. I agree about the kraft paper. I would like to have seen no kraft and poly completely sealing it up to prevent all moisture infilltration through the T & G. Has anyone ever seen this before? Really appreciate any input that anyone has.