Circulating damp outside air grows mold inside of buildings. Keep the inside of your building <50%RH. When the outside air is humid, dehumidification is needed for absolute humidity control. Every nite outside air is wet, rainy days outside is wet. Wet air grows mold. When outside air is wet and below 50^F, heating it to 70^F reduces the %RH to 50%RH. So ventilating with cold air and heating the space will dry the space only when the outside temperature is <50^F. Get a dehumidifier thats big enough to keep the space <50%RH. You need 1 pint of dehumidification per 20sq.ft. of floor space. Check epa web site for capacity and efficiency. http://yosemite.epa.gov/estar/consumers.nsf/attachments/dehumid_prod.pdf/$File/dehumid_prod.pdf?OpenElement