Moisture on the ceiling

Question from Scott: I have a hip roof on my house. It has a 26x26 great room with a pine tongue-n-groove vaulted ceiling in the center of the house. There is a circular attic around this great room (donut shaped). I have moisture problems in the winter and summer at the peak area of my vaulted ceiling. The rafters in the vaulted ceiling is stuffed with bat insulation, and no air space. Do I need to vent the peak? Do I need to install ridge vents? Do I need to pull the bat insulation out? Cupola?

Jake's Answer: 

Scott,

Yes, you have a moisture problem and proper ventilation is the answer. 

You should have both lower and upper vents, and all joists spaces need to be vented. This may be accomplished by running a continuous ridge vent and soffit vents. If the existing insulation has been compromised by moisture you may need to replace this insulation. It can be difficult to really properly ventilate these types of vaulted roofs.  You need at least 10” inches of insulation plus 2” of air space above it.

To get around this air space and thickness problem we have been using a spray on type foam called Icynene.  Check it out at www.icynene.com.  This is a really cool product that works great on vaulted roofs.