In situations where there is mold or mildew in dwellings, and it appears that it is coming from damp soil under the dwelling, some recommend laying poly on the soil. Wouldn't that exasperate the problem by trapping the moisture under the poly, causing mold to develop between the earth and the poly? If there appears to be plenty of cross ventilation, and the moist soil does dry out every year, but you still have the problem, wouldn't it be better to attach the poly to the underside of the joists? Or is this going to create even more problems because air can't circulate through the joist area, and the foundation vents are now in the joists, not allowing any air to circulate between the poly and the damp earth? Would it be better to install fiberglass bats between the joists with the vapor barrier down, and not install any poly at all?