Where back, the weather has been pretty good so it's been awhile. Anyway the other day I had a customer who had his roof done about 4 years ago. He install a 30 year laminate shingle, unfortunately they installed it over a vaulted ceiling area. He now has a bad condensation problem, and it,s so bad that his ceiling is staining. The old roof was cedar shakes, he did not have a problem till he changed the roof system to laminate shingles.

When roofing over a vaulted ceiling area you must have a 2 1/2 inch air space between underside of roof deck and top of insulation. more time that not when we re-roof over vaulted ceiling area you are removing cedar shakes. This type of roof system is more that likely venting itself, and owner's don't have problems. But when you change you roof system from shakes to adding new plywood deck and underlayment complete with fiberglass laminate shingles problems can arise.

What should be done? You remove strapping, set aside to be reinstalled. Cut fiberboard the width of the rafter space, and set between each rafter space. Reinstall strapping. Now push down on fiberboard to compress insulation 2 1/2 inches then nail 3 1/2 inch nails through strapping enough to keep fiberboard down. At ridges install continuous ridge venting. Important make sure that your fiberboard is compressed at out side wall or you will not have any intake. ridge vent acts as exhaust for air circulation.

HOPE THIS HELPS