Then this thread isn't for you because it doesn't get hot where you live.
No sane person would live in a home without a central HVAC in an area that gets real heat. Swamp coolers and those portable window A/Cs just can't keep up.
High humidity is worse, and it's for at least 6 months
Ok this is getting pointless. I'm just stating that I use air conditioner, and Hong Kong is so fking small the median apartment size is like 430 sqft. Most households don't need and can't afford a vent.
Also put foil-backed insulation over any single-paned windows you don't use. Or do what I did and cover only half the window if you still use the room occasionally.
And if you have an HOA that bans this, placing the insulation behind the blinds instead of directly on the window will do the trick and make it difficult to see what you did, especially if you keep the blinds closed or only open them partially and angled downward.