Up On The Roof (again)

Here is a little bit of a differnet view of the house that I don't think I've shown before. I like this because you can see all the way thru the house. We finished insulating the entire roof now and are ready to order the metal decking. I will be glad when the roof is done; the rest of the work moves faster. Pablo had some interesting questions about my last post and since I did not get to answer him when he first left the comments, I thought I would just answer now because some other people might have been wondering some of the same stuff.
As far as how much we are insulating; Alabama winters can and do get fairly cold. I think our average daytime temperature in Dec., Jan. Feb. is low 50's but quite often in the 40's and nights regularly go 30's but can get down in the teens. I remember one Christmas Eve night when I was a teenager it was 7 degrees. But here is the thing; your primary source of heat loss from inside your house is through the roof. There is some through windows and walls etc. but hot air rises and so it transfers itself out that way. It's not to keep the cold out so much as to keep your heating source from having to work so much by retaining as much heat as possible. However, in the summer, good roofing insulation does work by keeping heat out because of heat transfer. The roofing will heat up and in turn heat the decking, then the attic, then your ceiling etc. until it migrates into your living space. Good insulation and air spaces help prevent this. As do light colored roofs. Basically, insulate as much as you can possibly afford to.
Now, on the bullseyes on the roofing membrane; you would not normally use that membrane the way we did (which you may know). It would normally be put down directly on the plywood decking, under the shingles or whatever and when you nail down felt or this stuff, you are using short felt caps and it doesn't matter if you hit rafters or not because its in the attic. Now, this does bring up something I failed to mention. We don't have any attic in the living room/ kitchen area of the house, so what are we doing about that? When we nailed down the sleepers (the 2x4's that are sandwiching the insulation panels) we did take care to hit the rafters so that no nails would show on the ceiling. The insulation panels are not nailed but they do have metal clips on top of the sleepers holding them down. The fancy roofing membrane is nailed to the sleepers and glued also so we don't have to worry about nails showing from that. I hope I am able to explain this correctly, if not please ask more.