said by lazidazi :
Okay, now - please don't anyone get fussy with me for asking an ignorant question.
RE Xcal's pictures, insulating attic with rigid foam board on the bottom edge of roof rafters: When one does this, is insulation at/between the ceiling joists then not needed? Is the rigid insulation at the rafters all that's needed for the attic? [including, of course, what he's done on the gable ends, et al]
You use fiberglass insulation under the rigid board to create a higher r-value insulation while moving the thermal envelope. R-19 fiberglass is the most common under the rigid board which is R-13 for a 2" thickness for a total of R-32. If you can get more then R-19 under the rigid board that's great. Some people use foam instead of fiberglass.