The above drawing is from a new air conditioning building (designed 2020), an interior vapour barrier is stupid!
Why? The external vapour pressure is significantly higher (approx. 1kpa higher) than the interior vapour pressure in the air conditioning space, causing moisture flows toward and into the room.
However, the internal vapour barrier stops the flow, and traps moisture saturating the thermal insulation with water and destroying its thermal properties, and increasing the building energy consumption.
HKGBC recent asked for ideas to promote nett zero and lower energy consumption, the first step I suggest must be stopping architects doing stupid things!