Understanding Airflow: The Truth About Vents and Diffusers

That is where your infiltration is coming from. The window, the wall, whatever's on the outside is— whatever's on that perimeter is what the vent or AC unit or heating unit is trying to attack and trying to condition that space. So if you did a smoke test on that vent on the floor You got a wall right here, could be window, it doesn't matter. You'll see, you see the air come up, it'll hit the ceiling almost like a mushroom. You'll see it come up, hit the ceiling, and then curtain down and condition that wall. So you see it come up, hit the ceiling, wall, up, ceiling, wall. That's why plastic diffusers, which blows the air into the middle of the room It's not a good idea because it's trying to— again, it's trying to condition, attack the outside wall. So you should never close your vents. You should never use plastic diffusers. You should never block your vents because it's getting in the way of it doing its job, trying to condition the outside walls.