Abstract:Based on the definitions of air conditioning period, dehumidifying period and heating period, this paper puts forward the exchanging conditions and psychrometric process of ventilation system in residences. Because of the remarkable humid climate in hot summer and cold winter regions, the ventilation dehumidification becomes a more important part of the air treatment system. In order to improve the indoor thermal environment quality, new strategies must be founded to control both temperature and humidity of ventilation system.