Insulation after skylight removal

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carydf

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We removed a dozen skylights from a heated porch. Each old skylight cavity has been covered with 3/4" ply and the porch has been re-roofed. There is no venting from the old skylight boxes. There are two options for insulation:

a) Glue 2" solid insulation tight to the underside of the roof sheathing, fill edge gaps with canned spray foam, drill holes in the rafters to allow some venting, add a layer of R13 fiberglass insulation w/paper vapor barrier, then drywall over.

b) leave a 1.5" gap between the roof sheathing and the 2" solid insulation and drill holes in the rafters to allow some minimal air movement, fill edges with canned spray foam, add a layer of R13 fiberglass insulation w/paper vapor barrier, then drywall over.

Which option is best?
 

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Does the roof have a ridge vent to allow the moist air to escape? If you don't drilling holes (fairly large ones I might add) won't do anything.
 
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