Posted on May 23, 2011 by Scott Gibson
Ted Storm is in the midst of a construction project and at a point where he needs to make a decision about attic insulation. The unvented roof consists of standing-seam metal over synthetic felt and oriented strand board (OSB) sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen.
. Both HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. equipment and air ducts will be located in the attic of this house in Climate Zone 4.
Three insulation contractors are unanimous in their recommendation to spray a 6-in. layer of open-cell foam on the bottom of the roof deck.
While the advice is consistent, Storm is having second thoughts about his decision not to vent the roof.