If you don't have multiple zones you can still effectively have zones by opening/close the registers/vents. This will prevent hot or cold air from entering the

If you don't have multiple zones you can still effectively have zones by opening/close the registers/vents. This will prevent hot or cold air from entering the room. However, it will also increase duct pressure and that could be somewhat problematic. Either way, "smart vents" are on the market. They're ridiculously overpriced though and one could hack together an alternative for under $50 per vent (source: personal experience). Probably less if they are clever. Of course then there is the problem of running power to the vents or having sufficient battery. But that's an exercise left for the reader.