Nobody would worry about moisture in buildings were it not
for the multitude of moisture-related problems, one of which is mold growth.
Mold not only releases toxic particles into the air, mold actually “eats”
The microorganism extracts the carbons out of building
materials and uses them as nutrients to live; dry rot is a prime example of
mold’s destructive capabilities. Like all living organisms, mold needs
nutrients, air and moisture. All three ingredients are readily available in the
building envelope. Of the three, people can most effectively control moisture.
Where's All This Moisture Coming From?
Many building materials contain moisture. They are
hygroscopic, absorbing or releasing moisture until equilibrium with the
surrounding air has been reached.
A newly constructed building already comes with a lot of
extra moisture built-in, and drying continues even after the building is
finished. Construction lumber installed at 19% will dry down, concrete slabs
are still curing, the drywall could have too much moisture picked up during
storage and transportation. During the first year a building is supposed to
lose its extra moisture, and ventilation is necessary for a healthy start.
Many moisture problems develop later on. Ground moisture
could creep into the foundation and adjacent walls. Leaks from roofs or badly
installed windows are another source of moisture problems. Floods and other
disasters can catastrophically affect a building. Speedy drying-out after water
intrusions is essential to avoid additional problems.
Condensation is another dreaded source of moisture problems,
as it’s often hidden in the structure and can cause considerable damage.
Condensation occurs when warm air reaches cold surfaces. Buildings in climates
that require heating in the winter are more likely to develop condensation
problems, as heated air from the inside infiltrates wall cavities and
condensates on colder exterior materials. For example, damage from condensate
is often seen on windowsills. In severe cases the framing lumber and the siding
around windows are also affected.
When high moisture is allowed to remain inside a building,
problems are unavoidable. Unfortunately, moisture problems often start where
nobody can see them: behind walls, below carpets, etc. Noticeable signs are
buckling hardwood floors, lifting of linoleum floors, dry rot in wood, musty
smells or mold growing on walls. Sometimes there will be complaints about lung
irritation and unexplainable coughing. For successful repairs, the source of
the problem has to be identified and eliminated. Otherwise, the same problems
will come back.
Handheld moisture meters and Thermo-Hygrometers are the
instruments to use when tracking moisture problems. Pinless and pin meters are
available to measure the moisture content in wood, sheetrock and other building
materials. Accessories for pin meters allow for penetration deep into walls to
locate problem areas. Thermo-Hygrometers can measure relative humidity and
temperature; high humidity levels usually indicate a moisture source is close
The latest generation of moisture monitoring equipment has
the capability to record relative humidity and temperature or moisture content
of wood, sheetrock, concrete and other building materials at intervals anywhere
between 30 seconds and 24 hours. LEDs indicate when preset min/max limits are
exceeded. These devices are designed to monitor crawlspaces, attics and other
critical areas where moisture problems are suspected or leaks have been fixed.
Some systems use multi-function wireless transmitters. The
measurements from all transmitters in a test area are sent to a central
collection hub. The hub collects the data in pre-set time intervals. On-site data
retrieval is possible by connecting a PC and downloading the information.
Remote Web-based data retrieval is possible using cellular, Wi-Fi or Ethernet
Following is an example of two moisture problems in a
residence. A handheld moisture meter and a wireless monitoring system were
The monitoring system consisted of three transmitters and
one collection hub. One transmitter was installed outside under the roof to
record the outside relative humidity and temperature. The other two were
mounted inside. The collection hub was placed in a cabinet in the upstairs
living room. All readings were sent via cellular connection to a Web browser.
Two problems were identified: Water was dripping from a leak
in the roof into a window frame in the upstairs living room, discoloring the
paint and living puddles on the window sill. A musty smell in the basement was
constantly present, but there were not yet any visible signs of mold.
The leak in the roof was fixed. One transmitter was
installed inside the window frame to monitor the moisture content of the wood
and to see if the leak repair was successful.
More research was necessary to find the source of the musty
smell in the basement. Possible intrusion points for the extra moisture
included the foundation and the outside walls, which were partially under
At first, a handheld meter was used to obtain moisture
measurements from the sheetrock walls. Readings taken from the sheetrock on an
inside wall close to the floor showed 0.7%. In the opposite corner, moisture
readings were over 2%.
A series of readings was taken along all walls from the
floor to the ceiling. Walls not facing outside showed acceptable values for
sheetrock. All readings on the outside walls from 3 feet above the floor to the
ceiling were in the normal range. Mapping readings from the 3-foot level down
to the floor clearly indicated that the greatest moisture concentration was at
the base of the two walls facing the outside.
The carpet was also measured with the same meter: readings
showed the moisture increased toward the two outside walls.
To see if any changes in the high moisture levels occurred,
the third transmitter was installed in the wettest corner of the room. The
transmitter measured the relative humidity and the temperature, the moisture
content of the drywall and the surface temperature.
Moisture readings in the drywall stayed at a constant high
level for months; relative humidity readings in the wet corner were always
between 80%-90% and did not change much, even during the summer.
The structure and the ground around the building had soaked
up too much moisture during the wet winter.
Proper drainage needed to be installed around the building,
and the outside walls needed to be sealed to prohibit moisture migration. Then
the basement could be dried out successfully and hopefully will stay dry.
To preserve the health of a building and of the people
living inside, moisture problems need to be addressed as soon as they are
noticed. It does not help – and in fact, only exacerbates – the problem to
cover it with paint, install a new floor or perform any number of cosmetic
fixes if the source of the excess moisture has not been removed.