A.Bill Rose, architect and building researcher at the University of Illinois Urbana-Champaign, responds: There are four purported reasons to vent an attic space. The first is moisture control. Moisture control matters in the northern states, but in the humid South, only carpetbaggers would say that venting is necessary for moisture control.

The second reason for venting attics is to reduce ice dams, which are not a problem in Virginia. The third reason is to enhance the service life of asphalt shingles. How much effort and expense are you ready to put out so that the roof lasts 22 years instead of 20 years? (Use your own estimates of how long shingle roofs last — these are my...

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