One room in the house we smoke, but when a window is opened all the smoke is sucked through the ac ducts to the main intake which is in a hallway right outside all the bedrooms. I believe this is because the room is generally ~10 degrees warmer than the main part of the house which the hallway is off of because it is a large, open area which is less insulated because of a vaulted ceiling and many large windows. I am looking for a way to seal the room off from the rest of the house without disabling the functionality of the AC/Heater. I've found this HVAC Damper which I think could work, but it's a bit pricey, and it's supposed to be hooked up to a controller unit, so I don't know if there's a way to hook it up to either the fan or thermostat so it just opens when the AC/Heater/Fan is on, and the closes after. I had also been thinking about building a box with a large, one-way valve, but the only design I can think of is a bit beyond my fabrication abilities. Any help, hints, or suggestions would be appreciated, thanks.