I am really sorry but I do not know as we didn't require heating when we stayed here.
We loved everything about this Hotel when we visited in June - summertime - the room we had was excellent with double glazed windows and special sealed doors. It had a really large radiator panel which looked quite new - so I'd be expecting that the place was nice & cosy in Winter! btw, the staff were great & very friendly. Dave.
We visited the Hotel in August so can not directly comment. They did have a reasonably sized radiator in our room so would expect it to be warm. However, what level of heating is acceptable in January is a personal thing as I will accept it cooler than my wife.
Get an answer from Trierer Hof staff and past guests.