From what I've read it seems that it's a bad idea to cover central air conditioning vents. So what can I do to control the cold air coming through one vent without lowering the AC for the rest of the house? It needs to be easy to put on and take off as needed.

Is there any type of insulation or absorbing material that would absorb the cold part of the air and not block the airflow?

(Additional non essential info: We have one small room in the house that has a central AC vent, and because it's a small room it gets cold very fast. No window in the room.)

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    There might be a system balancing adjustment damper wherever that vent connects to the main duct in the basement. This adjustment is not convenient “to be put on and take off as needed” however adjusted correctly you shouldn’t need the ability to open and close on demand.
    – Tyson
    Commented May 24, 2018 at 11:13

1 Answer 1


They do make sheet magnets if your register is steel and not aluminum. Generally they have dampers in the registers for just such a reason. Just a word of caution, the heating and air conditioning system does require a certain amount of air to operate properly. If the system and duct work has all been sized properly then shutting off a small vent will probably not be a problem. But if the ducts are too small to begin with you could run into issues with the cooling coil freezing or liquid refrigerant getting back to the compressor. Or the furnace overheating. It is basically the same problem as a continuously dirty filter.

  • I agree. I don't think closing one damper would cause a problem, the cold air just goes to the other rooms. If you closed half the dampers...then problems could occur. Commented Sep 15, 2020 at 4:36

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