Hong Kong has a humid subtropical climate characteristic of Southern China. Summer is hot and humid, with occasional showers and thunderstorms and warm air from the southwest. With this climate characteristic, building envelopes and humidity control are important issues for many buildings in Hong Kong. It will affect building materials, air quality, comfort, corrosion, hygiene and even virus/bacteria inflections. This technical seminar explains the concepts of humidity control and its relationship with building envelopes. In addition, the speaker will also focus on the sharing of humidity control techniques in buildings and analysis of critical causes to comprise most building failures in hot and humid areas. It will further introduce different ASHRAE standards and publications related to humidity control in buildings in hot and humid climates.