Insulating a cathedral ceiling
Hello! Looking for some advice on current predicament. We have a new 2nd story addition consisting of vaulted 7/12 pitch (14′ max. ceilings), 2×12″ hand framed. Addition was framed with idea to vent vaulted ceiling from eave to ridge. Builder is proposing installing baffle at eave end ONLY in each bay and installing 10″ batting to ridge, which leaves a 2″ air space above insulation. We have installed Metal Sales Image II standing seam metal roofing with ridge vent on roof. I am now, in the 24th hour, second guessing this design and wondering if a hot roof would be more efficient and allow us to get highest R-value. We are in Lansing, Michigan, Zone 5. Contemplation points are as follows:
1) if batting is used, it seems wrong to me that builder isn’t extending baffles continuously from eave to ridge. Seems like moisture will condense over time in batting as well as dirt, dust, and air contaminants severely degrading the R-value over time. He says this is how it’s “always” done. Is it? I don’t want to be tearing down my drywall ceiling 10 years from now due to moisture damage and inability to keep room comfortable temp.
2) I had a spray foam company come and give an estimate on filling the cavity 5.5″ with closed cell, below a continuous baffle allowing 1″ air space. (They thought I was odd wanting to do it this way). My concern is finding a baffle that can hold up to the pressure of the closed cell without cracking (thus losing our VENTED chase). The company couldn’t offer a great resolution to this other that build your own baffle from furring strips and osb (time consuming) OR let us make it a HOT roof. So now I’m thinking maybe it’s better to make it a HOT roof? We are set up for a COLD roof. I have an open ridge with baffles already in place under the metal ridge cap. Sealing the eaves is easy, but if we pump foam in the ridge crack that’s been cut in the OSB, could I have potential moisture issues under the baffled metal ridge vent?
Our goal here is energy efficiency, maximizing R-value and saving on cooling/heating costs while maintaining the integrity of the sheeting/framing and new standing seam roof. I do realize that closed cell is not a “green” product.
Any input would be greatly appreciated!! Thank you.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part