Here is an option for those who already have a pre-existing HVAC system to bring in fresh air. This option can also be used as a "stand-alone" unit. (To directly connect in a room or rooms and supply fresh air and exhaust stale air)
This option is a Heat Recovery Ventilator (HRV) or an Energy Recovery Ventilator (ERV). This link will give you a listing of some manufacturers I found along with an explaination of what an HRV and ERV do.
(BTW...thanks Sharward for turning me on to this!)
http://johnlsayers.com/phpBB2/viewtopic.php?t=4384
The good thing about the Energy Recovery Ventilator is "SOME" models can "ASSIST" in humidity reduction. Be sure to read the info on HRV or ERV units and call the manufacturer if you have questions. I plan to purchase the Fantech ERV 1504 unit because of: price, the fact that it ASSISTS in humidity control, it can be tapped into an existing HVAC system, it has frost protection when the temps get down low, it has one of the better OVERALL warranties out of most of the the sites I visited (and I DID visit ALL of the sites I listed), it has an optional multi-function wall control I plan on putting in my control room, the unit does not automatically transfer the same humidity levels from one air stream to the other, it helps with ridding the air of mold, bacteria and airborne pollutants, it's equipped with "balancing dampers" which are suppose to balance the incoming and outgoing air levels to be equal (same amount of air going out as coming in) and the unit is suppose to assist in lowering energy cost from my HVAC system.
You make the call if this is the thing for you, but as far as bringing in fresh air in areas of the country (or the world) that have colder temps or high humidity levels, these seem to be a good thing to look into.
Stan