I live in the Houston area and have a 1975 two story home. I have noticed a very small amount of mold on the vents. After further inspection the mold is only on the downstairs vents. Also all of the downstairs vents have what looks like insulation right behind the vent. There is a round duct that is bare sheet metal and where the round duct transitions to the square vent there is the insulation material. The insulation is very nasty and blackish grey in color.
Why is there insulation behind the vents and why only downstairs?
Is the insulation causing the mold?
If i dont see any mold in the sheet metal duct can I assume it is only right at the vent? (I do have a access to a bore scope so I plan on looking as far as I can into the duct)
Thanks in advanced for any information on the issue.