www.epa.gov/iaq/moisture
Figure 1-7 Condensation behind vinyl wallpaper in a warm, humid climate.
Condensation and mold growth occurs behind the vinyl wallpaper on both
exterior and interior walls. Air leaks in the return plenum of the air handler
depressurizes the interior and exterior wall cavities. Warm, humid exterior air
is drawn from outside through air leaks in a heavy masonry wall.
Figure 1-8 Rainwater leaks in a rooftop parapet wall result in damaged plaster
and peeling paint. Rainwater is drawn into this brick assembly by capillary
action, and the moisture is aided in its downward migration by gravity. The
peeling paint contains lead and results in an environmental hazard as well as
physical damage to the plaster.
Figure 1-9 Interior plaster damaged by rain seeping around a window in a
brick building. The inside of the exterior wall is insulated with closed-cell
spray foam. Consequently, the wall cannot dry to the interior, so it retains
excessive amounts of moisture. At the point where the plaster on the window
return meets the brick wall, rainwater wicks into the plaster causing the
damage seen in this photo.
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