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Why Do I Have Mold In My Crawl Space? Part 4

Date Added: July 23, 2009 06:08:25 PM
Author: American Home Inspector Directory
Category: Real Estate & Home Inspection Articles

Why Do I Have Mold In My Crawl Space?

Part Four

This is the fourth and final article in a series on crawl space mold.

If you wouldn’t want to continuously breathe the air in your moldy crawl space, then you will probably be concerned to know that much of the air that you breathe in your house came from there.

Mold not only produces airborne spores, but it can also generate noxious volatile organic compounds (gases), which may cause a variety of symptoms including fatigue, nausea, headaches, respiratory irritation, eye irritation, inability to concentrate and dermatitis.


What can be done?


Barry Westbrook, Certified Industrial Hygienist, founder and President of DocAir (www.docair.com), a building systems evaluation and indoor air quality consulting firm, contributes, “In any discussion of indoor environmental quality it is important to acknowledge that there is a wide spectrum comprising the extremes from unsafe to pristine. There is also large variability in human sensitivities to mold spores and fungal particulates depending on sex, age, genetic makeup and overall health.

With these considerations in mind, the environmental condition of most homes should not be considered unsafe. However, air quality can definitely be improved once you understand a few building basics.


Indoor air quality basics


Keep crawl spaces dry


Westbrook continues, “Building codes require a minimum amount of crawlspace ventilation based on the length of the foundation perimeter. The intent is not to prevent moisture from entering the crawlspace but to allow any excess moisture under the building to evaporate. If the outside air is sufficiently dry and the amount of excess moisture is not too great, this process is adequate. Unfortunately, the outside air is usually much to wet to dry out the crawlspace. Particularly during the summer months, vented foundations transport moisture from the outside to the inside rather than the other way around. Condensation in the crawlspace can best be prevented by sealing it off from the ground and from the outside using a continuous liner.


Negative building pressure


Negative building pressure causes a continuous flow of air from the crawl space/basement into the first floor. Depending on the outside humidity levels, this influx of outside air can bring in large amounts of excess moisture and mold spores. This is a common cause of high humidity in basements.


DocAir’s Proof Positive™ System

DocAir developed the Proof Positiveä System to be an efficient and economical method of correcting negative building pressure problems.

The most important aspect of the Proof Positive™ System is its ability to effectively prevent the infiltration of outside air and at the same time bring in ventilation air that is filtered to the highest level of purity. The filtration standard is high efficiency particulate air (HEPA) which means that the system is tested to remove up to 99.97% of all particulate with a diameter of 0.3 microns or larger. Mold spores have a diameter ten times greater than this, so practically all of them are removed by this system. The human eye can see particulate down to 20 or 30 microns in size. HEPA filtration captures particulate far smaller than the human eye can see.


The installation is performed in three steps.


First, DocAir identifies major building penetrations using a blower door. The blower door increases the relative pressure between the house and the outside so that they can identify major points of infiltration.


Second, DocAir seals the previously identified penetrations using caulk, mastic, expanding foam, or weather-stripping, as appropriate.


Third, DocAir installs an outside air duct into the return air side of your HVAC system in order to place the house under slight positive pressure with respect to the outside.


The unit is outfitted with a HEPA filter to remove particulates from the outside air supply. After this phase is completed, unconditioned outside air along with dust, pollen, radon, moisture, and mold spores will not be able to infiltrate the house when the HVAC fan is operating. After you install this system you will notice a dramatic reduction in dust on indoor surfaces.

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