Okay, I searched and cannot really find my answer. I have an unfinished basement in 2 story with approximately a 1000 sq ft footprint. We had an energy audit a while back and one of the recommendations was to use spray foam in the rim joists to seal air and moisture that come in along the sill plate and the joist cavity. About 5 years back I had insulated the joists with fiberglass, but the energy auditor claimed that moisture and air still come in, especially in the summer when the A/C is running. He claimed this is one of the reasons that basements smell damp in the summer is that as the hot air rises warm moist air is sucked in from outside, but this would not be as much as an issue in the winter which is why basements don't smell as much in the winter.
Anyone able to verify/comment on this? Obviously the auditor's company wanted to help me by doing this, but I can't find much info out there on it.