If you begin shivering at 20C, put on a woolen sweater or the like. It's more comfortable anyway, because your body keeps the temperature that's optimal for it.
That got me curious, so I went looking: the official guideline for Brazil is in the range 23C - 26C in the summer, and 20C - 22C in the winter (http://portal.anvisa.gov.br/documents/10181/2718376/RE_09_20...). But I question that division between "summer" and "winter": it's in the middle of winter right now, and the predicted high temperature for today is 33C (it's been feeling like summer for several weeks already).
> If you begin shivering at 20C, put on a woolen sweater or the like.
It seems wasteful to cool the air from over 30C to 20C, just to have nearly everyone wear heavier clothing, instead of cooling it to something like 22C where everyone can use normal street clothes.
Oh I agree, I was talking (not clearly), from my own context where we don't have to cool the office, but heat it, in that case it's the efficient choice.
All air conditioner remote controls I've seen default to 24C whenever the batteries are replaced, so I believe 24C is the "standard" room temperature that AC manufacturers aim for.