Venting above an Insulated Cathedral Ceiling.
GBA Editor| Posted inEnergy Efficiency and Durabilityon
Situation:
Building with 6″ fiberglass insulation in rafter bays in cathedral ceiling on half the the house and 6″ fiberglass insulation in the rafter bays PLUS 1.5″ ridgid polystyrene pink board on the underside of rafters on the other half. Have had serious problems with ice dams over the years.
Due to storm damage, am going to replace entire roof at this time.
Queation: Would it help to VENT the roof above the insulation, given the different R values of insulation sue to different construction techniques?
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Replies
Tom,
Where are you - what climate zone? R-30 is the code minimum ceiling insulation in Miami. R-19 is inadequate anywhere in the US, and 1½" of XPS won't get you up to Miami's minimum requirement.
But, yes, roof venting along with a good air barrier and adequate insulation is the way to prevent ice dams.