If you have a hot water system (hydronics) you can use non electric zone valves on the supply OR the return line if this is NOT a loop system to balance out the heat where you want it.
If it is a hot water system you could also try bleeding out the air from the cold radiators.
If it is a Steam (vapor) system you should change ALL your air vents using the smallest orifice sized valve closest to the boiler.
By properly sizing your air vents the system will balance out properly.
If your not sure then HIRE A LICENSED Plumber to teach you how to properly maintain this GREAT SYSTEM