If your attic has passive ventilation, you might experience seasonal heat and dampness. Is your attic ventilation enough for summer? If not, temperatures could rise as high as 140 F. Even adequate passive ventilation gets overwhelmed on high heat super-sunny days. The answer is to exhaust hot attic air and exchange it for cooler outside air with a thermostatically controlled power ventilator (roof-mounted or installed just inside the existing vent). Then, when temperatures reach 90 F, it will kick on. Heat will exit, and when it's cold, moisture and condensation will be reduced.