Abstract: A crawl space ventilator includes a molded plastic self-contained support frame 20, with low voltage fan(s) 40 mounted therein. The frame 20 including a screened face plate 14 with adjustable hooks 22 or other such means for attachment to existing crawl space screens 12. On the upper surface of the frame 20 is a sloping rain guard 24, molded into the frame 20, to direct rain or irrigation water off the unit and vertical perforated tabs 26 on either side, that can break, off to allow for adjustment to for the ventilator to fit different sized vent screen 12 sizes. The tabs 26 have a secondary purpose, in that they have holes 27 that allow for nails or screws to penetrate through the holes 27 and into the foundation wall surrounding the crawl space opening 12, and is intended as an alternative method for installation.