Gary,

Its actually "likely" where the moisture barrier was not installed on the walls before the lattice and stucco was put on the home. Condensation builds within the walls and they mildew from the inside out. We had a house we cleaned that weeks later mildew grew again but just on the second floor. We treated again and same thing happened. I though the answer was to call a priest! The builder finally ripped the stucco off and found there was no moisture barrier on the second floor walls. SOMEONE SHORT CUTTED!

AC