1960's rambler attic has fiberglass blown into 3 gable vents and numerous sofits. last year we replaced all the windows new furnace and air . this winter i peeked up into the attic to see frost on the plywood below the shigles. live in minn.would a power vent be a good option? did find gabel vents had screens on them that were plugged removed sceens cleaned next night it was much cooler with air flow.?