Air Vent’s 20-watt solar powered fan Model NSP20WW provides exhaust ventilation for attics up to 1,500 square feet. The CFM of the fan is up to 1050 with direct sunlight to the solar panel. NOTE: Anyone can calculate the estimated CFM of a power fan once the attic square footage the fan can service is known by using the Home Ventilation Institute’s industry-accepted formula. (Attic square footage x 0.7 = cubic feet of airflow per minute to create 10-12 air exchanges in the attic per hour). For more information visit www.hvi.org.