After scouring the internet, this thread is the closest I've come to finding someone else trying to do what we are. We just purchased a 1955 Mid-Century Modern house with vaulted cathedral ceilings. We do not want to lose the wood ceilings. Instead we would like to insulate by using 1.5" foam and installing a second T&G ceiling on top of the existing ceiling. We are in Southern California. There is no venting in the ceiling and never has been any and the wood is all in great shape. The roof of the house was put directly on top of the T&G. I am hoping someone can tell us if what we want to do is feasible. Can a second T&G ceiling be installed with no air space, directly on top of Tuff-R foam over the existing T&G ceiling?