While out driving around today I saw several houses in a subdivision that all had this problem.
(https://i53.photobucket.com/albums/g73/Lovett1/DSCN1895.jpg)
This is a synthetic stucco siding; some call it EIFS I think. On one house it looked a little
like mold growing in between the studs on the outside surface.
Anybody seen this before?
Never on a wall.
I see effects similar on roofs here on frosty cold mornings. The roof will have a frost all over. Those with less well insulated ceilings will have the frost melting off between the rafters.
I wonder if it's related to some similar heat transfer or conduction thing? ???
Think Don nailed it...It would be interesting if you were to drive by on a few other occasions, at different times and during different weather conditions, and see if things have changed...
Unfortunately, here in the hot southeast, I see it a number of times in subdivisions that are just a few years old. Like already suggested, I've always attributed it to poorly assembled walls .... skimpy insulation, missing drain/vent planes, inadequate vapor retardents, etc. I'm convinced if the walls were opened and inspected ... a triving mold culture would be found.