Whether or not to ventilate a crawlspace is probably the most controversial issue concerning crawlspace design. Many building code require vents to circulate outside air. Research has now shown that crawlspace vents can be counterproductive. Introducing outside air into a cool crawlspace during summer, when temperatures are most conductive to mold and decay actually raises crawlspace relative humidity. This practice can easily produce relative humidity of 80-95%, even in dry crawlspaces with dry soil or vapor barriers. Experts recommend, after addressing all other moisture concerns, to seal the crawlspace and install a proper vapor barrier. If needing, a dehumidifier can be installed to condition the crawlspace.