Crawl Space Ventilation - Vents Below Grade

With an unconditioned crawl space (usually dirtthere is an opening in front of and below the vent.
covered with a plastic vapor barrier and openPersonally, I like to see the well dug a few inches
foundation vents) a home inspector does notdeeper than the vent, then the space filled with
want to see the vents below the level of the soil.pea gravel up until about 2" below the vent.
When vents are below grade, rain and runoffAnother issue is that often people block the vents
water are likely to enter the crawl space -- whichin an unconditioned crawl space. Although this is
can attract wood destroying organisms or lead tosometimes justified in winter, when there is a
fungal issues such as rot or mold.danger to pipes from severe temperatures, in
If vents are far enough below grade, the dirt canWashington State blocked vents in an
block the openings so air will not circulate. Theunconditioned crawl space are defined by the
vents will not ventilate! When home inspectorsWashington State Department of Agriculture as
see this condition, if vents cannot be fixed byconducive to attracting wood destroying
removing or grading soil, the inspector willorganisms. A state licensed structural pest
probably recommend that the client put in ventinspector should, in most cases, site blocked vents
wells. The most simple vent wells consist ofas a conducive condition. In the Pacific Northwest,
frames made from pressure-treated lumber.if pipes are wrapped, foundation vents can be left
However, metal or plastic vent wells, speciallyopen year-round most years. This basic
made for the purpose, can be purchased atinformation might not apply in severe climates or
building supply stores. The well is dug into the soil,in partially heated or "conditioned" crawl spaces.
in front of the vent and deeper than the vent, so