Try to explain this one to me??

[Greg Veal]

Chris,

It could be something as simple as the register has been turned off/louver damper closed, causing a sweating/condensation on the metal register.
Lots of people do that to save energy in regularly unused rooms. People sometimes close registers to help force air further down line to areas not getting enough air.
All sorts of reasons may be possible, including a real problem with the Mech. operation of the system.
Typical design of HVAC systems in Multi-Family properties, have been marginal to poor at best, typically due to cost cutting, space constraints for ductwork design, etc. Usually no design for balancing the system airflow, except by the registers.
By the way, I have seen mildew, mold, etc on Plastic registers as well.

[Christopher Rich Iii]

Thanks Barry.. I was just sitting here thinking a similar senario. Register vents in ceiling, warm air rises and condenses on cold metal air register vents, back of home faces SW. Fifteen years later this is what they look like. Any help on wording this in my report???

[Christopher Rich Iii]

Thanks Greg!!