Forced hot water? And you rent? Call your landlord immediately.

We have forced hot water heat in part of our home and our furnace guy told us to turn the thermostat up to 73-74 and keep it there when it gets to single digit temps. If a certain zone in the system isn’t calling for heat, in extreme temps there can be small stretches of pipe that are fairly close to exterior siding and if there isn’t constant demand for heat, they can freeze up if the house gets cool like that. Your landlord will know if this is an issue in your house.