It's very uncommon for homes to be as cold as 16C in Sweden, in fact if you rent you can demand that the temperature doesn't get lower than 18C, or 16C on the floor. It's probably because of better insulation.
The law in NYC is something to the effect that between October (I think) and March, if it's colder than X degrees outside the landlord must heat the apartment to 65F in the daytime and 55F at night.
