20C in wintertime is quite cool for North America, in my opinion. I think 23C is commonly considered "comfortable," but obviously that will vary significantly by individual.

Chicago building codes require 68F as a minimum for residential in winter conditions, so I think that's reasonable as a "habitable minimum yet not necessarily ideal" benchmark: https://www.chicago.gov/city/en/depts/bldgs/supp_info/chicag...

Wow. Obviously there are humidity differences during different seasons, but 23°C is probably the limit of "this is uncomfortably warm" for me if I set my thermostat above that.