Is Venting a Wall Recommended for Exterior Building Walls Covered with Foil-Faced Exterior Sheathing?
Our photo at page top shows a super-insulated building addition constructed by the website author (DJF) in1978. Walls were framed with 2×6 studs, insulated with 6″ of fiberglass batts, and sheathed on the wall exterior with 1-inch “High-R” foil-faced foam insulating board. An additional layer of 15-pound felt was installed over the wall, topped with furring strips to give a 1/4″ air space ( for a total wall R-value of about R28) over which we installed plywood T-111 grooved building sheathing. The wall interior surface received a continuous 6-mil poly vapor barrier over which drywall was installed. This was an early experimental “superinsulated” design in response to soaring home heating costs during the U.S. oil price spikes in the 1970’s. By 1983 we heard that concern for possible wall cavity condensation had led manufacturers of foil faced sheathing to recommend corrugated vent strips nailed at the sills and wall top plates to ventilate the insulated wall – an idea that seemed odd a
