A.Contributing editor Ted Cushman responds: With few exceptions, installing shingles on an unventilated roof deck will void the warranty. The fact that your local building department okayed the installation probably won’t help: As one warranty (from the Canadian firm EMCO, which makes Esgard shingles) states, "Where local building codes have specific [ventilation] requirements that differ from the National Building Codes, the more stringent requirement must be followed."
In fact, as you might guess from that quote, just having the roof ventilated may not be good enough. The shingle maker has to agree that the ventilation is up to its standards. If the warranty excludes installations with "improper ventilation," that language may be enough to deny a claim.
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