Thanks you guys.....I grew up in agriculture(different kind).....Know all about the alien invaders.....I was going to pull air from under the house...exhaust through the attic. The house is built on a foundation...about 3 feet between the ground and the floor. Was thinking of using a ducted fan so i could just screen off the bottom of the duct to keep out the vermin....using a small closet...about 4'x2'....thanx again