I have a large attic with a ridge vent, but no soffit vents or other vents for air intake. As such, the attic gets very moist and cold/hot. I would like to finish the attic for additional living space. As such, would blow-in insulation be suitable to insulate and seal the attic prior to finishing? As I live in the Northeast, would I need to extend the rafters to get adequate insulation? Also, would I remove the ridge vent and leave in the floor insulation?
Insulating in small spaces is often tough. When your rafter is only 8" deep, you can use only 6" of fiberglass insulation as the rest needs to be saved to allow for ventilation, which is hardly enough. Additionally, it is very difficult to get insulation into such a tight space.
However, spray foam insulation can fill in the entire cavity. It has a higher R-value and doesn't need to be ventilated, and in my view, the best way to insulate a finished attic or cathedral ceiling. The Money Pit Guide to Insulation might be a useful resource. Good luck with the project.