In the hot summer and cold winter zone, due to its typical climate characteristics, moisture-laden outside air poses real problems for proper ventilation, air-conditioner sizing, and strategies to overcome the reduced dehumidification capacity of more energy-efficient AC systems. Based on the papers [1-3], this paper provides further the occurrence and characters of moisture resource. After a detailed presentation of the technical issues, this paper gives specific recommendations for providing adequate ventilation, moisture control and dehumidifying in hot-humid climates.