7 inches of R-38 really necessary?
If you already have R-30 in insulating value, it's certainly more than one inch. (It could be one inch of fiber glass fluff plus several inches of somethine else underneath.)
If it is really just one inch of insulation over the ceiling panels or plaster then the R-value is certainly much less than R-30.
Fiber glass batts intended to provide R-40 of insulating value will actually provide much less if squashed to less than the intended thickness.
It is okay for insulation in the ceiling to extend above the tops of the joists. If you wanted to add an attic floor at a later date, you would need to shim the tops of the joists so the floor boards or panels don't squash down the insulation.
The disadvantages of crab apple trees. In summer, the apples are too sour to pick and eat. In winter the birds come and leave dropping all over the place.
Last edited by AllanJ; 10-05-2012 at 10:06 PM.