Health Concerns
How to Identify
the Cause of a Mold and Mildew Problem
Mold and mildew are
commonly found on the exterior wall surfaces of corner rooms in
heating climate locations. An exposed corner room is likely to be
significantly colder than adjoining rooms, so that it has a higher
relative humidity (RH) than other rooms at the same water vapor
pressure. If mold and mildew growth are found in a corner room,
then relative humidity next to the room surfaces is above 70%.
However, is the RH above 70% at the surfaces because the room is
too cold or because there is too much moisture present (high water
vapor pressure)?
The amount of moisture in the room can be estimated by measuring
both temperature and RH
at the same location and at the same time. Suppose there are two
cases. In the first case, assume that the RH is 30% and the
temperature is 70oF in the middle of the room. The low
RH at that temperature indicates that the water vapor pressure (or
absolute humidity) is low. The high surface RH is probably due to
room surfaces that are "too
cold." Temperature is the
dominating factor, and control strategies should involve
increasing the temperature at cold room surfaces.
In the second case,
assume that the RH is 50% and the temperature is 70oF
in the middle of the room. The higher RH at that temperature
indicates that the water vapor pressure is high and there is a
relatively large amount of moisture in the air. The high surface
RH is probably due to air that is "too moist." Humidity is the
dominating factor, and control strategies should involve
decreasing the moisture content of the indoor air.
For information about
mold and related health hazards please see, http://www.epa.gov/mold/moldresources.html |
