What are the remedies for mold found on two Heat Pump air vents/registers and in the HP air handling unit?.
Moisture is the cause, but is it due to inadequate insulation in the exterior walls? The mold does not appear regularly (i.e. on the two air vents and no other vents is the mold seen). A UV light was installed five years ago by a HVAC contractor and the air filter is changed every 30 days without visible evidence of mold. A dehumidifier is run in the basement regularly as a percaution. Ducts were cleaned 4 years ago and we are planning another cleaning, though the contractor inspection of the ducts did not report any mold then or now (new contractor giving estimate), but ducts have accumulated enough dust to warrant another cleaning.