Use and Care Guide

Keep Crawl Spaces Drier
The practice of adding vents to crawl space walls is
meant to help dry out the crawl space area. However,
vents actually allow moisture to enter the crawl space,
and do little to help it dry out.
Moisture that enters through these vents clings
to floor joists, batt insulation, HVAC equipment
and plumbing fixtures. In this moist environment,
mold and mildew can quickly degrade the space’s
contents, as well as compromise indoor air quality.
In addition, wood-eating insects, dust mites and
small creatures can enter through the vents to take
up residence.
A popular alternative to the vented crawl space
is the unvented, properly insulated crawl space.
Rigid foam insulation serves an important role
in an unvented crawl space, helping keep the
area dry and the home more energy efficient.
THERMAX
™
Sheathing polyisocyanurate insulation
and STYROFOAM
™
Brand XPS Foam Insulation
products can be left exposed on crawl space
walls as stated in ICC NER-681 and ESR-2142,
respectively.
Rigid foam insulation on the
interior of unvented crawl
space walls keeps the crawl
space warmer, reducing the
potential for condensation
and related moisture issues.
Moist air in a vented crawl space can migrate
to the interior of the home, increasing
indoor humidity levels. One consequence of
increased humidity is wood components and
furnishings absorbing moisture, which can
cause warping and swelling.
Photos courtesy of Jeff Tooley, owner of The Healthy Building Company
®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow
5
®™Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow