hi im plumbing my base board heaters i want to have 2 thermostats up stairs and down stairs my home is a open florr pan now i really dont understand zone valves from what ive read the thermosta controls the valve but do i use a 2 way or a 3 way whith the 3 way i was under the impression i would put the valve in the supply linne and the other port would run to the return but that idea was blown to peices after i found out they are normally closed so how would i get any heat it would just retun to the boiler please explain this or send me a diagram on how to pipe please help also do i need flow valves thanks