5 min read

Mold in Crawl Spaces

Published on
May 18, 2023

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Oftentimes we encounter homes with elevated “Mold Load”.  Remember this term, it is becoming more and more popular in Naturopathic circles.  “Mold load” is defined as the cumulative effect of mold throughout the home, accounting for the unseen mold,  the seemingly small and insignificant amounts of mold in a home, and major mold issues. It is the overall condition of a home, relative to mold toxins, mold spores, and mold growth and is an attempt to indirectly educate the public with the idea that home health is to be looked at holistically, and should not be isolated nor remediated, by visibly moldy and visibly non-moldy areas. Additionally,  It is very difficult to quantify what a dangerous “Mold Load” is, however, anytime a family member is suffering ill effects from mold in the home, it is a home with elevated and unhealthy “Mold Load”

Crawl spaces are usually associated with homes that have a large “mold load”. The cumulative effect of a moldy crawl space, along with other seemingly small issues throughout the home, becomes a real issue for mold sensitive people. Crawl spaces are a less expensive way to build a home in which much of the electrical, heating, and air conditioning and furnace can be placed under the home. These are convenient for the builder, however, are prone to moisture and mold growth.   Even building techniques that, at the time of construction, were considered the industry standard, have ventilation issues, moisture issues, groundwater issues, and associated microbial growth.  In my 15 years of experience in the mold remediation industry, I have often said, “show me a crawl space and I will show you some mold”.  It is really that prevalent.  

The reason for mold growth in crawl spaces is not as complicated as one might think.  All structures are on the edge of mold growth.  We are always within just a few degrees, or a few humidity points, and a fresh air allotment, or a lack thereof, of encouraging mold.  It is widely accepted that mold will grow on a surface that is within an environment of 60 percent humidity or more.  Along with this, we are constantly on the edge of “dew point”.  In other words, when the combination of surface temperatures and humidity align, the water in the air will condense on the cold surfaces.  Precisely why we have dew on the grass in the mornings. Once a moisture issue is present, it is only a matter of time before mold will begin to thrive, particularly, if the moisture issue is not corrected.  

Ventilation codes are about the same for crawl spaces as they are for attics.  For crawl spaces, you are required to have, unless local or state codes are different, 1 square foot of ventilation for every 150 square feet of underfloor space.  So a home with a 2000 square foot “footprint” would need to have the equivalent of 13 square feet of ventilation.  There is quite a bit of flexibility relative to how to divide up the 13 square feet of ventilation.  There are also “exceptions” in which the ventilation requirements are significantly less, or non-existent.  Some of these exceptions include a vapor barrier, or a full vapor-proof membrane being completely sealed onto the floor and up the walls partially. I've never been able to wrap my brain around the thought process of installing a vapor barrier, which will often trap moisture, you will need less ventilation.  

It has been my experience that ventilation is the most critically important variable in reducing the mold load within a crawl space.  I am sure that every climate is unique in determining the best way to handle a crawl space.  However, here in Utah, in many cases, I can see that the “vapor barrier” actually exasperated the problem.  Particularly if the homeowner noticed mold getting out of control, and tried to add a vapor barrier to stop the growth. When this happens, the crawl space now has elevated mold and mold spores, and a plastic barrier simply traps moisture and mold underneath. As discussed earlier, you now have even better conditions to increase mold growth and increase the overall “Mold Load” of the home.    

The time to address mold in a crawl space is during construction.  Hopefully, the lumber used in the crawl space was not exposed to moisture, and hopefully and just as important,  does not have mold on it.  The next factor is moisture. Hopefully, the home was “dried in” with a roof before winter or rain set in. If during the building process, you can keep the mold load low, and the moisture low, you have a fighting chance of keeping the overall “Mold Load” low.  After moving in, If either or both get out of balance, mold will be an issue.  This can become a real health issue, particularly when the crawl space is being utilized to hold the furnace and HVAC ductwork.  No furnace or ducting is airtight, and simply through the venturi effect, you will pull mold, mold spores, and toxins from the crawlspace through the HVAC system, and deliver it throughout the home.  I have heard really sad stories of literally thousands of dollars being spent in an attempt to remediate the issue, with very little or no relief.  

Thankfully, the Pure Maintenance 2 step VaPure system can return a crawl space and the home to low “mold load”.  The first step is called InstaPure, in which a peracetic acid VaPure fog fills the entire volume of the space.  All mold and mold spores, along with any bacterial load will be completely denatured. In the second step, called EverPure, the technician will apply a solution that is widely used as an antimicrobial product in manufacturing.  Every surface in the crawl space will be coated with trillions of tiny carbon spikes with a positive electrical charge. No poisons, no heavy metals, no triclosan's, no phenols, no bleach is involved. These tiny spikes create a covalent bond with every surface in the crawl space. This process will make the crawl space very inhospitable to mold in the future.   Mold spores will not have the luxury of bouncing around within the space in hopes of finding moisture.  As soon as a spore touches an electrically charged spike, it is effectively torn apart. The cycle of mold finding moisture, sporing, and those spores finding moisture and sporing, and having this repeat over and over again will not occur.   This along with added ventilation, if needed, is simple and more importantly, a Fresh Start to a Healthy Home.