I have a very small cast iron radiator which works great, but when really cold temperature hits outside, it is not enough to heat that particular room (and it is on the third floor so 2nd zone is not an option now).
I want to add baseboard radiator to run along the side of the wall next to cast iron radiator. Given that small radiator is sufficient 80% of the time, I would like to be able to shut off baseboard one and turn it on only when needed.
How can I connect both? And what type of shut off valve to use for baseboard one?