Abstract: A sealed attic insulating and roof ventilating system includes a plenum formed in part by a barrier material attached to adjacent pairs of rafters and having a radiant or reflective upper surface and a corrugated lower surface to which an insulation material may be secured. This arrangement creates an uninterrupted air chamber or ventilation plenum between the barrier material, the adjacent rafters, and the roof decking through which exterior air can circulate unimpeded from the lower vents to the upper vents of the roof. The circulation through the ventilation plenum prevents moisture from accumulating or condensing under the roof decking and warping the roof decking, which ultimately leads to deterioration of the roof decking and failure of the roof covering, and eliminates ice damming on the top surface of the roof covering.