Cathedral cieling...adding insulation

Jason Duke
1/11/2012
I have a metal roof and an unfinished second story home. Upon checking my insulation, I realized something that may be a problem. First, my roof joists are 2x10, and they insulated them with batting. They used R19 faced insulation, and because it doesnt fill the cavity, there is a channel between it and the roof...which I think is OK. The problem is, this is how the cathedral ceiling in the living room was done. That means its heavily under-insulated (drwall, R19, airspace, deck, roof paper or whatever, and then metal roof). Since that part is finished, is there any way to properly insulate that area without taking down drywall? Any solution I can think of involves pumping the cavities completely full of insulation, thus cutting off any airflow under the decking between the joists. I do have radiant barrier decking, if that matters at all.
Todd Miller
Isaiah Industries, Inc.
5/4/2012
Do you have any ventilation in the cavity currently? And if so can you please describe to me what you have?
Eric Novotny
An informed customer is the Best Customer!
5/5/2012
You have two options when it comes to insulating that ceiling, dropping the drywall or removing the roof. If the roof assembly is currently vented, it will need to remain as such unless you actually can add sufficient insulation to prevent any condensation and your air barrier detailing is spot on. Converting a vented roof to an unvented roof is impossible via blowing in more insulation from below. Your radiant barrier decking has nothing to do with the ventilation of the roof and will not eliminate any of the potential moisture issues. If you are getting ready to replace the roof, there are several ways you could do it and covert that roof into a hot/insulated roof effectively.
Guest User
1/11/2013
The roof assembly and attic is currently vented. The cavity on the vaulted ceiling is ventilated by using R19 in a 2x10 rafter. It if forcibly cupped to allow air to flow. There is no baffling, but the effect is the same. My question is that I have another area upstairs that is very very similar, and it is unfinished, and I need to know how to properly insulate it considering I don't have enough space to put R30 insulation, AND maintain the air space for proper ventilation. Ive been told that since it has a radiant barrier and a metal roof, R19 insulation exactly as it is installed will provide more than enough insulation...but that doesnt technically meet code requirement I don't think since its R30 for my area.
Jason Duke
1/11/2013
The roof assembly and attic is currently vented. The cavity on the vaulted ceiling is ventilated by using R19 in a 2x10 rafter. It if forcibly cupped to allow air to flow. There is no baffling, but the effect is the same. My question is that I have another area upstairs that is very very similar, and it is unfinished, and I need to know how to properly insulate it considering I don't have enough space to put R30 insulation, AND maintain the air space for proper ventilation. Ive been told that since it has a radiant barrier and a metal roof, R19 insulation exactly as it is installed will provide more than enough insulation...but that doesnt technically meet code requirement I don't think since its R30 for my area.

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