Although it may seam more difficult to close your foundation vent with a concrete block it is actually not that hard and far more cost effective. The franchise companies sell their “vent covers” for around $25 each. To close your vent with a cement block will cost you about $3. Vent covers will not keep out the winter temperatures or keep the mice out (I have see them chew through metal)....

Homes built on a crawl space needs ventilation! Right? Right! Notice I did not say “Needs vents”, that’s because a crawl space does not need the foundation vents (that go outdoors) if, and I quote:IRC 2006 and 2009, Section 408.3Unvented crawlspace Ventilation openings in under-floor spaces specified in Sections R408.1 and R408.2 shall not be required where:Continuously operated mechanical...