On Feb 25, 10:24*am, Bert Hyman wrote:
Guy wrote:

The worst heat happens when there is no wind. *If there is no wind, your
wind-powered vents will not turn, and the temperature in your attic will
rise - probably to 140f or more.

What "killed" our shingles was time.

Convection moves air from the soffit vents to the roof vents.

--
Bert Hyman * * *St. Paul, MN *

high attic humidity from lack of ventilation can also shoten roof
lives, and worse damage the decking