Hi, I am nearing (or I thought I was) completion of an ICF home in upstate NY. I have cathedral ceilings with 2x10 rafters for a roof. I used 8" r30 insulation between the roof sheathing and the ceiling, and now am dealing with moisture problems on the underside of the roof. I have some mold growth and had some ice build up that began melting and dripping through the ceiling. Obviously, I am not getting enough ventilation on the bottom side of the roof. It is a metal roof. For about two thirds of the roof there is only access from the soffit. The other third is in the loft where there is a knee wall crawl space where I can access the rafter spaces. I am wondering if it would be possible for a spray foam installer to spray the underside of the roof from the soffits? And also if there are any other solutions. Currently I have inserted furing strips and turned them on their side to improve air flow. Any and all suggestions would be greatly appreciated! Thanks, Eli

So you have a wood truss roof with blown in insulation (fiberglass or cellulose) within an unconditioned attic?

It is fiberglass insulation. I thought the 8" would allow a one inch air gap, but it turned out it expanded to fill the whole space in some spots.

so the roof is sheathed with plywood of some type with a membrane and the metal above that? 8" of fiberglass is well under code anyway, so you'll need to add insulation. I suggest "biting the bullet" and redoing the ceiling - remove the insulation, install some good vents such as 1-1/2" strips of foamboard onto the sides of the rafters with 1"foam board sheets fastened under that, then closed cell cellulose and sheets of foamboard under the rafters. the basic problem, other than the insulation depth is poor air sealing, so the insulation must be airtight. (Fiberglass, while cheap is crappy insulation anyway and it leaks air lilke crazy.) Aim for R50 at a minimum, or R-60.

If for some reason the insulation is in contact with the metal, it will always be a problem nomatter what else you do. you need a membrane under the metal to catch any water & send it down the roof.

Bob, Yes, the metal has a membrane under it with the sheathing below that. Removing the ceiling is not in our budget right now. I know r30 isn't the greatest, but it is what I thought would fit and allow an air gap. Any other suggestions until we can do it right?

Like the other guy said, nothing can be done except to redo it properly. There really aren't any temporary band-aids. Live with it until you can get the time & money to do it right.

I would recommend spray foaming the underside of the roof if you only have such a narrow attic area. Cathedral ceilings are nice but the problem comes back that the attic space is tight or in some areas, non existent. That is why I chose to go the steel SIP roof route on my cathedral ceiling. No way to get cellulose at a proper depth with stick frame or truss frame cathedral ceilings. A lot of people go the route of stick frame and then spray foam on the underside of their cathedral ceiling. It can get expensive and you still have the problem at the top plate and soffit areas. Best solution for a cathedral ceiling in my opinion is a steel SIP. You get your structural, insulation, air/vapor barrier and soffit, all in one shot. Much stronger than a stick frame roof and a lot lighter also. Plus you don't have to vent the steel SIP.