Humidity is the amount of water vapor
in the air. The ability of the air to
carry water vapor increases with an increase
in air temperature. In water damage restoration,
we are most concerned with the relative
humidity. The relative humidity will help
determine how fast materials dry. It relates
to how much more water the air can hold
at a given temperature. Warm air will
hold more moisture than cold air. If we
take a colume of air that has a relative
humidity of 50%, and raise the temperature
of the air 10 degrees, the relative humidity
will decrease. More than any other factor,
the relative humidity helps control the
rate of evaporation. Because relative
humidity increases as the air temperature
decreases, a low temperature will result
in less evaporation. In a cold environment,
evaporation will be low.
A flooded room with 100% relative humidity
will never dry, no matter how many dryers
you have running. When the air is at 100%
humidity, the same amount of water that
evaporates from the carpet will fall back
into the carpet. In order to dry materials
in this environment, we must reduce the
There are several methods to remove
the water vapor from the air. If you live
in an area where the humidity is extremely
low, you just open all the windows. Since
humidity always seeks to balance itself,
it will leave the building. If you don’t
live in a low humidity environment, use
a dehumidifier. A dehumidifier is a machine
that removes moisture from the air. As
it reduces the humidity, the walls, floors,
carpet and pad dry at a much faster rate.
In basements or natural flood situations,
it is a must, for without one, the dryers
merely circulate warm, moist air, and
little or no drying takes place. Dehumidifiers
remove high humidity from the room, and
the dry air will pull moisture from floors,
pad, walls, and carpet.
There are three types of dehumidifiers
on the market today. The most well known,
is the standard refrigerant dehumidifier.
It works by passing moist air over cold
coils. When the saturated air passes by
the coils, the air temperature is reduced
to the saturation point. The moisture
then condenses on the coils and runs into
a collector bucket. It is a very simple
process and acts just the same as when
you have a cold drink and the water condenses
on the glass. A portable, high capacity
refrigerant dehumidifier can remove about
5 gallons in 24 hours and reduce the humidity
to 40% at 80 degrees F. The advantage
of refrigerant humidifiers is that they
are the lowest cost humidifiers readily
available. The main disadvantage is that
as the air becomes cooler, the performance
deteriorates rapidly. Below 68 degrees,
most refrigerant dehumidifiers will stop
removing moisture completely, although
the DrizAir 50 will operate down to 55
degrees. The performance of any dehumidifier
will vary with changes in temperature
Another type of dehumidifier uses a
desiccant to remove water from the air.
A desiccant is any material that has a
high affinity to water, high enough to
dry moisture from the surrounding air.
There are two types of desiccants: absorbents
and adsorbents. Absorbents go through
chemical or physical changes as they absorb
water. Salt, sugar, and lithium chloride
are all absorbent desiccants. On the other
hand, adsorbents do not change when picking
up water. They hold moisture on their
particle surfaces. Cotton and silica gel
are both adsorbents. Most desiccant dehumidifiers
use either an absorbent like lithium chloride,
or an adsorbent like silica gel as the
A desiccant dehumidifier works by passing
the flow of moist air through a perforated
cylinder holding the desiccant. This cylinder
turns slowly, allowing moist air to pass
through the perforations. As this happens,
moisture is absorbed. As the material
would soon become saturated, it has a
system of drying a portion of the desiccant
wheel with heat.
PRINCIPLES OF DRYING
Given any drying situation, there are
three factors that can be managed for
fast successful drying: temperature, air
movement and humidity control.
- AIRFLOW CIRCULATION
- TurboDryers are designed to deliver
a high volume laminar airflow over or
under wet surfaces for speed drying.
Airflow speeds the rate of evaporation,
helps prevent mold growth, and reduces
the risk of secondary damage. Circulating
air speeds evaporation by moving the
“boundary layer” of saturated
air that hangs near wet surfaces. The
moist air is whisked away and replaced
with dryer air.
- MOISTURE CONDITION
- The moisture condition of carpet,
cushion, flooring and walls along with
other structural materials and contents.
- HUMIDITY CONTROL
- Using TurboDryers to speed the rate
of evaporation in an enclosed area can
cause humidity to escalate. As humidity
elevates, airmovers become less effective
and the rate of drying slows. It is
vital that TurboDryers be used with
adequate dehumidification. For safety,
indoor humidity should not exceed 60%
Rh. For maximum drying porous materials,
indoor humidity should be maintained
below 45% Rh. This may require the use
of DrizAir Dehumidifiers. Even lower
humidity between 25-40% Rh is helpful
for drying saturated, dense materials
such as walls and floors. This is possible
To assist in the drying process, the
heating or air conditioning system of
the structure should be regulated. When
dehumidifiers are not available, exhaust
fans in the attic, kitchen and bathroom
can be turned on to remove some humidity.
A thermo-hygrometer may be used to determine
the indoor relative humidity.
It is possible to dry both the stretched
in carpet and synthetic cushion at the
same time on many flood jobs. TurboDryers
are used to force air under the carpet
so that a cushion of air floats the carpet
off the floor. Along with humidity control,
the high volume airflow will usually dry
most carpet, cushion, and flooring.
When hardwood flooring is present under
wet carpert, strong consideration should
be given to removing carpet for drying.
Consideration should also be given to
removing water damaged carpet cushion
when it has a non-porous plastic “skin”,
when it shows signs of severe wear or
in contaminated situations.
DRYING OUT YOUR HOME
Floodwaters affect a house in 3 ways:
- The water damages materials. Wallboard
will disintegrate if it stays wet for
too long; wood can swell, warp, or rot;
electrical parts can short out, malfunction,
and cause fires or shock.
- Mud, silt, and unknown contaminants
in the water not only get everything
dirty; they are also unhealthy.
- Dampness promotes the growth of mildew,
a mold or fungus that can grow on everything.
DRY THE CEILINGS, WALLS &
Flood-soaked wallboard should be removed
and thrown away. Plaster and paneling
can often be saved, but you still need
to get air circulating in the wall cavities
to dry the studs and sills. Different
approaches are used for different materials.
WALLBOARD – If
dirty floodwaters soaked the wallboard
at least 4 feet aboce the floor, take
down all the wallboard and replace it.
If the water was less than 4 feet deep,
remove the lower 4 feet of wallboard.
You can fill the gap with new 4ftx8ft
wallboard sheets installed sideways. If
you have Styrofoam insulation-or no insulation-and
the wallboard was soaked with clean rainwater,
you can dry the walls without removing
the wallboard b using the technique explained
below for plaster walls. But you will
need to remove wet insulation if it is
PLASTER WALLS –
If the plaster or wallboard is clean and
in good shape, you can drill or cut ventilating
holes in each wall cavity. Place holes
low enough so they will be covered by
the baseboard after the wall dries out.
Open up the wall on both sides of interior
walls. For exterior walls, drill or cut
holes only on the inside of the house.
However, if there is wet insulation, you
will have to remove the plaster or wallboard
in order to take out all the insulation.
CONCRETE BLOCK –
The cavities in a concrete block wall
will drain on their own. The water will
not damage the concrete like it will wood
WALL COVERING –
Vinyl wall covering seals the wall and
keeps it from drying out. Wallpaper paste
is also a favorite home for mold and mildew.
For these reasons, you should remove all
wall covering that got wet and throw it
out. (If vinyl wall covering is loose
on the bottom, you may be able to save
it by pulling it off the wall up to the
flood level. Clean and reapply it after
PANELING – Carefully
pry the bottom of each panel away from
the wall. Use something to hold the bottom
away from the sill so the cavities can
drain and dry out. You can nail them back
into shape after they and the studs dry
out. However, if there is wet insulation,
you will have to remove the paneling in
order to take out all the insulation.
FLOOR – Air needs
to move around flooded floors so they
can dry out. This usually means that you
must remove the floor covering. Because
floodwaters contain mud and dirt, most
soaked floor coverings should be thrown
away. Keep a piece of all discarded floor
covering so the adjuster can tell its
Air needs to circulate below the floor
to dry it out. If the crawl space of your
house is flooded, pump it out. Remove
any plastic sheets, vapor barriers, or
insulation from underneath the floor.
(Be sure to replace them when the floor
and foundation are completely dry.)
If a house with a basement was flooded
over the first floor, remove finished
basement ceilings, or cut or drill homes
between the joists to allow circulation.
Don’t cut or drill near electric
lines or pipes.
CLEANING FLOOR COVERINGS
- Small throw rugs can be saved and
cleaned in a washing machine.
- Indoor/Outdoor carpeting can be hosed
off and hung up to dry.
- Large area rugs and any rug with
foam backing should be discarded. (Usually
only valuable carpets are worth the
cost of professional cleaning.)
- If wall-to-wall carpeting was soaked
with floodwaters, it usually must be
thrown away. To make the job easier,
cut it into strips and discard it in
pieces that are small enough to carry.
- A wall-to-wall carpet that was soaked
by clean rainwater can be left in place
- Remove tile, vinyl, or linoleum flooring
if it is warped, loose, or has a foam-runner
pad (which should be thrown away).