Rather than butt in on the other discussions, I would like to start a new on on a similar subject. I also have a hot second floor in the summer and cool in the winter even though it has fiberglass insulation. The rooms all have cathedral ceilings so I can not put more insulation in. Beside not enough fiberglass I am sure the mice have tunneled throughout the fiberglass further reducing its effectiveness.
My plan is to insulate my +100 year old farm house by taking off the tin roof and decking, removing all the fiberglass insulation, and sistering 2×4’s to the 8″ rafters. The cavities would be foamed, covered with 1/2 inch decking, then 1″ furring strips with another 1/2 inch deck. On top of that I would put new standing seam roofing. Screened vents would be installed at the bottom and ridge of the roof.
Am I crazy, any problems, has anyone done this before?