Basis Vents Open Or Closed? If, however, you cowl the naked ground in your crawl space with an permitted vapor barrier materials, you only want 1 sq. foot of vent for each 1,500 square ft of house. Translated, this code requirement means that you want 1 sq. foot of http://deangmqtz.canariblogs.com/a-quick-analysis-about-identifying-criteria-for-sub-floor-installation-installation-12490885