Achieving desirable comfort conditions in a place where the climate is hot and humid can be challenging. This paper investigates the environmental performance of a number of buildings by Geoffrey Bawa. This paper firstly reviews Bawa’s architectural works in a chronological order and studies his approach to facade design for controlling internal comfort conditions in the ‘selective’ mode. Secondly, the paper focuses on one of the most representative facade design, ‘Monsoon Window’ facade in his works to investigate its environmental performance and explores its potential wider application in the hot and humid climate zone. The limitation of the original ‘Monsoon Window’ was identified through simulation with parametric variations. The findings show that selective use of a well designed ‘Monsoon Window’ can enhance the indoor environment and substantially reduce the reliance on air conditioning in office buildings.