Where to staple paper-faced insulation?
Is it better to staple paper-faced insulation to the face or to the side of the studs? Is this topic addressed in the building code?
Roe Osborn, Woodbury, CT
Gene Leger, a home-energy consultant and former building official in Nashua, New Hampshire, replies: When I was a code-enforcement officer in Nashua, I banned side-stapling of paper-faced insulation to studs and joists for two reasons: fire safety and energy-efficiency. Section 320 of the 2000 International Residential Code (IRC) addresses the fire rating of insulating materials.
Side-stapling creates air channels next to the studs and reduces direct contact between the facing and the back side of the drywall, which creates more airspaces. Coupled with holes in the framing for wires, these channels and airspaces are like raceways for fire to spread through a house. The potential for flame spread is reduced greatly when the insulation’s facing is in direct contact with the drywall.
There’s also an energy penalty because fibrous insulation is dependent on trapped air. Side-stapling not only creates the aforementioned air channels and airspaces but also compresses the insulation. Compressing the insulation decreases the amount of trapped air the insulation can hold and so reduces R-value. Air circulating within the wall cavity also decreases R-value.