Moisture Control
With a simple hand-held device, moisture in wooden members of the substructure
in the crawl space can be determined. Readings over 20% are conditions
conducive to pest infestation as well as wood-decaying fungi, mold, and mildew
growth. Relative humidity in a crawl space should be kept below 55% as
well. (Which is hard to do with open foundation vents and
humidity levels at 80% or higher in the Southeast much of the year. See
below)
Whenever moisture readings in excess are discovered a moisture control plan
is often proposed to remedy the problem. Sometimes the plan is as simple
as repairing a plumbing leak. Sometimes guttering, land drainage, or other
exterior problems must be address. Often the moisture that naturally
accumulates in a crawl space must be controlled via the methods described below.
Moisture control in a crawl space has changed a lot in the
last few decades. In the past, it was suggested that a crawl space be
ventilated to keep moisture levels down and wooden members of the substructure
dry. With the advent of central air conditioners, this point of view has
changed.
Outside of drainage or a pipe leak, the most common source of moisture in a
crawl space is the condensation that gathers on air ducting under the home.
This moisture drips and lays on top of the ground or vapor barrier (if
installed) only to be wicked back up into the wooden members of the sub-floor.
The Department of Energy has also found, particularly in the Southeastern US,
that high relative humidity leads to moisture troubles in a crawl space as well.
So instead of ventilating the crawl space with the outside air, it is now
suggested to close and seal the foundation vents, install a poly-vapor barrier,
and export crawl space moisture with a commercial grade automatic dehumidifier.
Installing these systems has shown increased air quality inside the home,
reduced mold and mildew inside and under the home, and better energy efficiency.
To learn more, scroll down to Conditioned Crawl Space below.
Poly-Vapor Barrier
This is the most basic of moisture control in a crawl
space. A stand-alone poly-vapor barrier impedes ground moisture from
rising to the wooden members of the home. Most times, these are left with
"breathing" room around the edges of the barrier next to foundation elements.
These moisture barriers are often dislodged and damaged by people or animals in
the crawl space. They also do nothing to export moisture from under a
structure. Bill's Exterminating Company/Peeler Environmental will install these upon request,
but we advise a better, more continuous type of moisture control as described
under conditioned crawl space.
 Foundation Ventilator
For homes without sufficient airflow beneath them, we can
install additional foundation ventilators or install automatic foundation
ventilators where current manual ventilators reside. A better form of
moisture control under the house is to close/seal it and export the current and
on-going moisture to the outside as described under conditioned crawl space. We
sometimes use these for open crawl porches when we close/seal the rest of the
crawl space. While we will offer foundation vents, we recommend that all
of our clients consider a conditioned crawl space installation.
Conditioned Crawl Space
There are various levels of moisture control in a crawl
space. The most effective and economical is installing what is known as a
conditioned crawl space. By installing a poly-vapor retardant to 100% of
the ground, closing and sealing the foundation vents, and finally installing a
commercial grade dehumidifier, we can keep moisture levels of the wood and
ambient air at acceptable levels. Keeping these levels in check controls
and prevent wood damaging fungi, mildew, mold, and even insects while providing
a much cleaner environment under the structure resulting in cleaner air rising
into the living space.
These are examples of clean/conditioned crawl spaces.
Dehumidifiers installed:
Encapsulated Crawl Spaces
Encapsulated crawl spaces are also available. The
only difference with the conditioned crawl space is that encapsulation involves
installation of a poly-vapor retardant to the foundation walls and piers, sealing, and
anchoring it. (labor intensive) There are also various options to this
installation as well, pending the customers desired level of controlled
crawl space under their home or place of business. Full encapsulations go
further to reduce moisture infiltration by blocking capillary moisture entry
into the crawl space via the foundation wall. This also has a beneficial
by-product of increasing energy efficiency of the home by retaining warm air in
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crawl space in the winter, lessening the load on your heating system. We
can take this a step further by installing foundation wall insulation as seen in
the following photo.
Conditioned and Encapsulated Clean Crawl Spaces are available with poly-vapor
barriers of 6mil (opaque), 8mil, 12mil, and 20mil (all in white). 20mil is
the thickest and most durable. A 20mil poly-vapor barrier is much like
adding a nice white, clean floor to your crawl space.
Click these thumbnails for photos from an encapsulated crawl space installed
by Bill's Exterminating/Peeler Environmental
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Crawl Space Service Options
We can add the following service options to the moisture
control methods above:
- Mass Moisture Export (drains, sumps)
- due to
some land grading and construction techniques, rain water often enters a crawl
space. When possible, we divert the rain before it enters the crawl space
through downspout extensions and re-routing. In some cases, a sump basin is
needed. Crawl space water is directed toward a commercial grade basin and
sump system that will then export the water outside of the foundation wall into
daylight away from the home. We also install gravity flow foundation
drains at the foundation wall-ground juncture in the crawl space and route the
water to a sump or through the foundation wall to daylight away from the
structure.
-Wood Debris Removal
-all wood
debris on the crawl space floor should be removed before a poly-vapor barrier is
installed (wood remaining on the ground under a crawl space is a condition conducive
to wood destroying insects (termites))
- Subfloor Treatment to reduce
mold/mildew
- a crawl
space dehumidifier will reduce proliferation of mold and mildew over time as the
moisture levels are reduced under a structure. Customers who want existing mold/fungi immediately
remedied under a structure may elect to have the subfloor treated. This
treatment is applied to all of the exposed wooden members of the subfloor.
The material kills surface mold/fungi and penetrates the wood protecting it from the growth of wood decay
fungi, mold, and mildew.
Monitor the Status of Your Crawl Space Humidity
Some clients want to be able to see the measured results of their conditioned
crawl space. With this device and a remote sensor located in the crawl
space, you will always know that the humidity levels are in an acceptable range
and that the installed dehumidifier is functioning properly. (hasn't
accidently become unplugged or circuit breaker tripped)
In the picture to the left, the middle section represents the readings of the
remote sensor in the crawl space. This customers crawl space humidity is
now at 39%. Excellent!
These are available at the time of installation or can be added to any
existing conditioned crawl space system. Even homes without a conditioned
crawl space can benefit from knowing the humidity levels under the home.
We can install these for you or offer them to the "do-it-yourselfer."
Contact us for more information!
Word of Warning for the Curious Homeowner
If any of this information has sparked your interest to go
into your crawl space and have a look around, please use a NIOSH respirator to
protect yourself from mold/mildew/fungi spores and other airborne matter that
may irritate your lungs and/or make you ill.
Contact Us today to see what Bill's
Exterminating/Peeler Environmental can do to make your crawl space a drier, healthier,
and more energy efficient part of your home!
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