A. As long as the crawlspace is reasonably dry, vents on only three sides should be adequate to vent the crawlspace. If there is good drainage (the slope would indicate that this is likely), and a plastic ground cover is installed, there shouldn’t be much problem. But while vents on all sides may not be needed, don’t forget that it is much easier to install them during construction than to cut them in later, if the need ever arises.
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