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About Dehumidifiers For
Drying Water Damage
Dehumidifiers are needed to
properly dry most jobs.
Excessive humidity in a
structure is typical after
water intrusion. Then, as
the contractor uses rapid
and massive airflow to
evaporate moisture from
materials, much more water
vapor is added to the air.
Evaporation will slow and
materials will not dry
quickly unless the humidity
is reduced.
High humidity must not be
allowed to continue, for two
reasons. First, sensitive
contents and materials run
the risk of absorption,
delamination, swelling, and
so on. Second, indoor air
quality is threatened by
mold and other biologicals,
which grow best when
moisture levels are
abnormally high. Microbial
growth is the number one
indoor air quality problem
in the nation, according to
a 10 year study by Healthy
Buildings International (Indoor
Air Review, July,
1994). And the primary cause
of excessive microbial
growth is abnormal moisture
- excess moisture content in
materials, and excess
humidity in the air. Just as
mold can grow in a shower
stall that never dries out
thoroughly, it can grow
explosively after a water
damage situation if the
humidity is not controlled.
While the issue is
complex, several criteria
help determine when
dehumidifiers are required.
- Whenever the indoor
humidity exceeds or will
exceed 60% Rh,
dehumidifiers are
required for rapid
drying, for mold
reduction, and for
indoor air quality. The
Environmental Protection
Agency, the Hardwood
Flooring Association,
and the Institute of
Inspection, Cleaning and
Restoration all
recommend that indoor
humidity should never
exceed 60% Rh.
- When porous
materials like carpet
and carpet cushion are
wet, the most cost
effective indoor
humidity for drying is
40-50% Rh.
- When structural
materials like walls and
floors are wet, the most
effective humidity for
drying is below 45% Rh,
and a target of 25-45%
Rh is helpful. In many
cases, dry air is
extremely beneficial in
reducing the need for
reconstruction costs, or
for mold problems days
or weeks after the job
is apparently complete.
It is true that not every
job requires dehumidifiers
during water damage
restoration. For example,
when the outdoor humidity is
below 40% and the
temperature is above 60 F,
dehumidifiers may not be
necessary if doors and
windows can be left open
safely
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