Under Oregon law—specifically ORS 90.320—landlords have a clear duty to maintain "adequate heating facilities" that conform to code at installation and stay in good working order throughout the tenancy. The dwelling has to remain habitable, meaning if the heat's out and it's freezing, that's a big problem. No, there's no magic number like "must keep it at 68 degrees," but courts generally view a non-functional system as a habitability violation, especially when temps drop low