I have always heard 72°;F
4/7/2018 at 1:08 PM
Personally, talking in Celsius, I like 20-22°. I prefer to not wear a blanket or sweater. ;) Now when I sleep, 18° feels cool...but then I have a blanket.
Because I was curious what the internet had to say, I did a little search. This is what I found...
https://simple.m.wikipedia.org/wiki/Room_temperature
https://www.quora.com/What-is-room-temperature-in-Canada
https://www.quora.com/How-was-72-degrees-established-as-a-normal-room-temperature
I think that insulation and drafts in the home need to be considered as well as personal metabolism (some folks are natural self-contained heaters...and some not so much). What you eat can also affect how comfortable you feel at some certain temperature compared to what others feel at that same temperature.
12°C is too cold. It is okay for an empty building, but not proper for comfortable living.