We’ve started using a lot of Dense Pack Cellulose (DP Cellulose) insulation. While a great insulation product, it has presented us with some installation challenges. One being how to vent rafters. While the manufacturer of the cellulose tells us that we can use a hot roof system, good ole’ builder stubbornness tells us that we should vent. One reason to vent is to allow the insulation to dry to the outside. The other is to keep the bottom of the roof sheathing dry.
With conventional fiberglass batt insulation you use a foam baffle product like Raft-R-Mate to keep the insulation off the bottom of the roof sheathing. However DP Cellulose would crush the foam vents. So we’ve started to double sheath our roofs. The pictures below show: 1) DP Cellulose installed, and 2) double sheathing with furring strip installed.