Quote Originally Posted by SoCal gunner View Post
Yes, it's the supply register. No return in this room.
Well that's the thing then. When the heat (or air) comes on, the dynamics of the whole thing change. What if it's a scorching hot day and the HVAC is running the whole time or the majority of the time? Now your fresh air is coming from the vent, not from under the door. And is that going to outrun your exhaust and start pushing the air out underneath the door? And now you've got the supply air and the exhaust vents on the same side of the room if you only have the two vents over there, far from the door... so smoke will probably hang in the air over near the door. I'd probably have to put in 4 vents, I couldn't resist; 1 in each corner of the room. Then I'd use a relay to toggle back and forth between the two sets of vents - running the ones near the door when the HVAC is running and the two far from the door when it's not. I tend to get technical like this but it's sure satisfying when it all works like a charm in the end... that and I love relays...