This is the final article in a two-part series on crawl spaces in residential
construction. For more information about DocAir's Proof Positive™
technology designed to solve the crawl space moisture problem, please
contact us.
Toxic
Mold
Toxic mold is a monumental problem for homeowners, commercial property managers,
schools and insurance companies. Moisture trapped in wall cavities promotes the
growth of fungi and other microbial contaminants, which can result in
significant health problems and major property damage. Billions of dollars are
spent each year to treat the symptoms. However, unless negative building
pressure is corrected, the mold will return.
Indoor air quality professionals must be able to identify moisture pathways into
buildings; however, they often overlook the crucial role that negative air
pressure plays in causing mold problems by forcing moisture into a building.
Barry Westbrook, founder and President of DocAir (www.docair.net),
an indoor air quality consulting firm, said, “The volume of air entering a
building must equal the volume of air leaving. This is basic physics. Because
homes, offices and schools are constructed more tightly than ever to save
energy, air lost to the outside through various routes (often through
ventilation fans) results in negative air pressure. Negative air pressure sets
the stage for a number of IAQ problems, such as excess moisture, mold and even
radon gas."
The Problem
There are three things that destroy materials in general, and wood in particular
— water, heat and ultraviolet radiation. Water is by far the most important. A
dirt crawl space under a home is a very bad idea. The earth has very high
humidity in the soil. This water vapor moves easily into the crawl space and
upwards into the house. Mold, insects and structural damage are the consequences
of moisture intrusion.
Mold thrives and reproduces by producing airborne spores by the millions, and
some molds are toxic. Mold spores are in the air everywhere. All they need to
grow is organic material such as wood, the right temperature range, and
moisture. Dirt crawl spaces have the humidity necessary for mold growth.
Humidity levels from 50 percent to 90 percent are easily found in dirt crawl
spaces that have never flooded.
Mold can grow on dirt, insulation, framing and even under carpet. Mold destroys
organic materials as it feeds on them. Mold reproduces by producing millions of
floating airborne spores, which some people are very sensitive to. Spores can be
dormant for many years, waiting for the right conditions to grow. Some molds
produce mycotoxins, such as the black mold Stachybotrys. There is a solution.
Mold will not grow when the humidity levels are reduced to below 40 percent.
The natural airflow in a house is from bottom to top. This sucks the moist air
and everything in it up into the living areas of the home. Mold spores, odors,
humidity and critters create a very unhealthy environment for people. Many
people are allergic to these things, and don’t realize that their dirt crawl
space is affecting their health.
Dirt crawl spaces are great places for bugs to live and reproduce. Insects and
critters of all kinds love damp environments and wet materials. Rot and decay
occur in damp environments causing structural damage.
Moisture is the prime factor that causes structural damage. Over time, rot and
decay from a moist environment damage framing and steel structural members. Dirt
crawl spaces do not have to be wet or flooded to be extremely unhealthy. Heating
and cooling costs are higher in a home with a vented crawl space.
The Solution
The encapsulated crawlspace can be combined with other devices and techniques to
prevent indoor air quality problems. A dehumidifier equipped with a humidistat
can be placed in the crawl space to further protect the homeowner against
moisture intrusion. With a few minor adjustments to the HVAC system, the home
can be placed under positive air pressure, meaning conditioned air is forced
out. In many homes, negative building pressure actually sucks air from the crawl
space into the home, providing an avenue for mold spores and radon gas to enter.
Under positive pressure, these potentially harmful agents are forced to the
outside and exit through the foundation vents or the building skin.
Until the construction industry fully grasps the concept of relative humidity
and the damage that vented crawl spaces can cause, homes will continue to be
built with foundation vents. The best way to prevent moisture problems in your
crawl space is to encapsulate it. Crawl space condensation is both costly and
preventable. Ask yourself, what reason is there to allow your home to rot away
beneath your feet?
Toxic
Mold