:mad: We had our heat pump replaced and all the ductwork replaced. Before they completed I expressed concern about moisture. There had never been a problem before. After 5 visits we still have condensation on a bedroom duct grill and a bathroom duct grill which is ruining our ceiling. My question is what could be the problem? Flexible ductwork replaced rigid ductwork and a high effieciency unit with an environmental control thermostat. We have heard don't touch the thermostat, it is incorrectly pressurized, and the heat difference from the skylight is causing a problem. So now what??

Without the benefit of seeing the problem firsthand, it sounds like the duct insulation is insufficient, the ceiling insulation has been displaced, the supply airflow is too low, or a combination of all. Cold surfaces attract moisture; if the surface temperature is lower than the dewpoint of the surrounding air, condensation will occur.