If a Jew turns on the heat on Shabbos

Hi,

If a Jew lives in a building in which another Jew turns on the heat on Shabbos for himself, and it's cold enough outside that leaving the building is not an option, then one may remain inside. One would not be obligated to close the vents in his individual room.

(Rav Moshe Feinstein, Igrot Moshe Orach Chaim 1:123)

Have a great day,
Mordechai