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Closing registers to control A/C?

12 years ago


I have a 3-story home, where the bottom level is a basement. When I turn on A/C, the basement is too cold and the upper floor is not cold enough.

I know a two-zone system would be best, but my central unit is just one zone. So I'm wondering is it ok to just close all the registers in the basement to force as much air out the upper floors to help this problem?

I asked a few local hvac contractors and some say yes, this should be done while others say no, doing this will cause cold static air to reside in the ducts leading to the closed registers and cold static air will cause moisture and mold problems over time. They say that all registers have to be fully open when using A/C to minimize mold and moisture problems in ducts.

Who is right and who is wrong? Can someone enlighten me? Thanks in advance!

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