Why vent in an unvented roof design for snow region?
In Joseph Lstiburek’s book ‘ Builder’s Guide TO Cold Climates ‘ ,in discussing unvented roof designs, he says ” In extreme snow regions it is necessary to add a vented air space between the roof cladding (shingles) and the rigid insulation to flush heat trapped due to insulating value of the snow…”
Why does this heating of the cladding require venting ? condensation ? ice dams ?
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