bbhack wrote: ↑Fri Jan 13, 2023 4:37 pm That air is not coming from the attic but from the return. The return air should be 70F or whatever the air temperature was when the thermostat said stop. If it's getting that cold between the return intake and the supply registers, it sounds like you really need the ducts to get reinsulated. I guess it's possible that they were not insulated initially, which would make your bills crazy.
or, if the return duct or unit is in the attic, the return duct work is breached in the attic.
We had something similar happen at work with an attic unit. The AC would run normally in the cool of the morning then by the afternoon wouldn't cool enough to turn off. After crawling up in the attic I found panel had fallen off. Reinstalled and all was good.