Automatic Foundation Vents

Calculating Number of Vents Needed:

• 80%-90% Polyethylene Ground Cover: One vent per 150-250 sq.ft. of crawl space depending on moisture conditions.
• No Ground Cover: One vent per 60 sq.ft. of crawl space.
• Some codes allow one vent per 600 sq.ft. with ground cover, but many experts believe this is too little ventilation. Vents should be placed within 3' of corners and near dead spaces to provide cross ventilation. A minimum of 4 vents is always required.

Automatic foundation vents close at 2°C(35°F) and open at 24°C(75°F).