It chokes the blower and raises static pressure. Drag the dampers and watch the gauge tell on you.
Manufacturer limit is 0.80 inches of water column. Past that the blower moves less air, not more.
Residential blowers are rated to move their air against 0.80 inches of static pressure. The average system we test in Atlanta is already sitting at 0.94 before anyone touches a vent.
Close half the registers in the house and you are not sending that air somewhere better. You are making the blower work against a wall, pulling less total air, and shortening its life.
An undersized branch. A flex run crushed behind storage. A trunk that was never sized for the addition somebody added in 2004.
Those are duct problems with duct fixes, and none of them are solved by a damper. Balancing gets you the last fifteen percent once the ductwork itself is right.
Typical installed pricing on a single-system Atlanta home. If yours is not typical you will hear that before we quote, not after.
Static pressure across the coil and filter, CFM at every supply and return, and a temperature split at the plenum. You get the sheet whether or not you hire us for the fix.
When a run is simply too small for the room it feeds, no amount of balancing fixes it. We pull the undersized flex and replace it with correctly sized rigid or hard-drawn.
Mastic on every joint, boot and plenum seam, then a blower-door verified leakage number. Most Atlanta attics leak a quarter of their conditioned air before it reaches a room.
The last step, never the first. Once the ductwork can actually carry the air, we set every damper to a measured number and label them so nobody guesses later.
Undersized returns are the most common cause of high static pressure we find, and the cheapest to fix. Usually one added return solves what a new system would not.
"Static pressure was 1.1 and nobody had ever measured it. They added a return and the upstairs finally holds temperature."
"I had been closing downstairs vents every summer for six years. Turns out I was slowly killing the blower."
Name the room and roughly when the house was built. That tells us most of what we need before we arrive.
(404) 555-0176The airflow test comes off the bill if you have us do the work.