venting per square feet for crawl space
You only need vents if you have a crawlspace that has soil on the bottom. A basement or cellar does not need them. A crawlspace requires 1 square foot of ventilation opening for every 150 square feet of floor space. In addition, a ventilation opening must be within 3 feet of each corner of the space. There are exceptions to this code; let me know if you would like them.