My 45 yr old home in Atlanta,GA has an 800 sf (25x32) crawlspace containing 2600 cu ft. The dirt portion is covered with 2 layers of 6 mil plastic sheeting. Furnace, fan, and evap sit on a 10'x10' slab in the crawlspace. Current crawlspace temp and humidity aver. 68 degrees and 64 percent. Outside temp/humidity 92/41. Dewpoint 67. Trying to reduce musty crawlspace odor and humidity being sucked into a/c system. Can I cover the 4 outside air vents in the concrete block foundation and hook up a portable humidifier? Do I need to worry about how much outside air will be taken in, after sealing the 4 vents. Any other suggestions? Thanks for your response.