Domestic buildings in 36 sqm and 45 sqm were manually examined to see the appropriate window design in supplying recommended ventilation flow rates, which is 30 ach for warm humid regions. The detailed window design to be checked is position, dimension and style of windows. This study showed that in a very slow outdoor windspeed, the indoor air velocity and the amount of air velocity approximately 1 m/s, the small domestic buildings require no one fifth the floor area, as it is known before, but at least one half the floor area. Moving from suburb to city centre, similar buildings design requires more and larger openings in order to meet health and well being of residents.