My baseboard heat in the kitchen runs along the left wall as you look into the kitchen. The heat can just continue in a straight line into the new room.
The question is how to handle the return. My father mentioned that we shouldn't run the return under the new floor because it will be exposed (even though it will be an enclosed area). He suggested we raise the baseboard on the wall a bit and run a 1/2 return pipe underneath the fins. The old & new baseboards won't line up in height where they join but we could always put something in front of it.
I haven't had a chance to talk to the contracters yet, but I was wondering what people thought of that idea and whether having a section of the pipe go under the floor could cause problems with the cold weather (Eastern PA region). I think their plan is to run the baseboard all the way around the room & go under the floor to get around the exterior door.