[groveport]

Does circulation of air inside the structure affect the amount (or lack of) the green/black growth on the outside? Does the presence indicate the structure is not built properly in relation to overall ventilation, insulation, or permitting heat to build in the attic and cause a sweat?

[ballengerb1]

Usually not anything to do with how the home is built. Is the mildew on the shaded side of the building?

[joypulv]

Homes built properly allow moisture out through the wood, insulation, Tyvek or Typar, and the weep holes in the vinyl siding. After that, you are dealing with the outside. The mold on the outside is from not enough sunlight and too many trees and a damp climate. You have to wash vinyl siding so the mold doesn't pit into the design if it has one.

Moisture (and heat) in attics has to get out through soffit vents under the eaves, gable vents, ridge vents, or other types of roof vents.

Anywhere in a house it's important that moisture not condense inside a wall or roof, where it in water form rots wood and molds insulation. That's why you have faced insulation or plastic sheeting on the inside of the walls and breathable Tyvek type material on the outside, and a breathable siding - wood, vinyl, wood composite, concrete, stone, brick.