I have a room which is getting too hot during winter and I want to disconnect the hot water baseboard in it from the heating system. Problem is that heating system is a loop and room is in the middle. Do I have to open the wall and rewire the pipes behind it ? Is there a less extensive solution ? Could a zone valve help here?
If you put the housing back together you will see that there is a movable damper that allows you to block airflow and reduce the amount of heat that gets transferred to the room.
If you are sure you don't want it to put heat into this room, you could remove the finned radiator part and replace that section with a straight copper pipe. That will allow other rooms that this loop serves to continue to get heat. A "zone" valve will affect all the radiators on that loop which is OK if that's what you want.