So fiberglass batts 12" thickness. The goal is to not let the insulation become compacted or have gaps between unconditioned and the conditioned space.
When a drywall nailer is fastened to the top plate of a wall that means if projects into the attic space. The fiberglass forms an arch over the protrusion.
Is the most preferred method to slit the kraft paper and hollow out fiberglass so it sets flush with the future ceiling plane? Is there a gain doing this…assuming the insulation would otherwise just have a crown in the attic meaning still the same thickness?
Best Answer
no.no.no. don't slit the paper. its there as a vapour barrier. having your insulation humped up over the backing is no issue, as long as your vapour barrier and insulation are complete and with full integrity. just make sure that there are no gaps between the adjacent insulation and your humped piece of insulation (ie. where cold air can get down against the cold side of the drywall. here in Ontario, nobody has used paper backed insulation for years. we have the requirement of a seamless plastic barrier, taped, pocketed and sealed at all penetrations to make a giant air balloon out of every heated space. the logic is the same for any place on earth, even if you are working with old materials or new materials that use old technologies.