Hi All! I have a new constuction home with dual zone HVAC system, 1 zone per floor as standard setup. My question is for the return air system, should the return vents be active in both zones when only one of the zones is actually heating or cooling? I found it strange that when the heat was off downstairs but was on upstairs, that all the returns in the house were active, on both floors. Felt like it was sucking all the hot air from downstairs while it wasn't replenishing it. Any help or insight on this would be appreciated to see if I have a problem or if this is the way it should be! Thanks!