Crawl space vents/Foundation vents

Crawl space vents/foundation vents

Most people are familiar with crawl space vents or maybe you call them foundation vents.  We see them on most every home with a crawl space.

Expectations of the crawl space vent:

Vent for moisture. The original idea for these vents is to allow air in to the crawl space and circulate air hoping to help the crawl space dry out.

Old rumors say to open the vents when the temperature is above 60 degrees and close before winter to prevent freezing.

The house stack effect: As the home breathes from the bottom to the top, air is sucked in from the bottom or these crawl space vents the home pulls the air up through the home and out the attic. A home literally pulls unconditioned air in from the bottom and pushes it up through the living areas.

Our manager here compares your foundation vents to basement windows, they are essentially the same thing. If you would not leave you basement window open you should not leave your crawl space vents open. 50% of the air in our home comes from the air in the crawlspace below, some through leaky air ducts, holes drilled for wires or pipes, poorly insulated floors, etc.

Open crawl space vents provide the perfect habitat for mold growth. Temperature above 60 degrees, moisture humidity above 55%, and dead organic material (like the wood of our floor joists).

Open vents also allow for bugs to get in the crawl space. Spiders, snakes, and rodents follow hunting the bugs or for refuge from the conditions outside.

Reality of crawl space vents:

Allow for humid air

Bugs, Rodents, other pests