connecting baseboard on infloor radiant system

Hi

I installed a very simple system with cast iron boiler (slantfin) and zoned per floor with thermostats. So 1 manifold with loops per floor (per zone). I am doing an addition and bringing from the boiler 1" pipe and return to a manifold that will serve the addition which has 2 floors. I am thinking about installing a zone valve with thermostat after the return manifold for the first fland would like to install for the second floor 2 baseboards. I was wondering what would be the way to do this if I can? Thanks, Marc.