Can a Dehumidifier Kill Mold in Your Crawl Space
                     Does a Dehumidifier Kill 
Mold from Crawl Space?
The Common Myth: Dehumidifiers Kill Mold
Widespread Belief Moisture Reduction Only Dormant, Not Dead
Many homeowners mistakenly The primary function of a While a dehumidifier can make 
believe that simply running a dehumidifier is to remove excess mold spores dormant by removing 
dehumidifier will eradicate mold moisture from the air, creating an humidity, it does not actively kill or 
growth in their crawl space. environment less conducive to mold eliminate existing mold colonies.
growth.
Why Mold Thrives in Crawl Spaces
Crawl spaces are notoriously damp environments, often hidden 
beneath our homes and easily overlooked. Several factors 
contribute to their high susceptibility to mold:
• High Humidity: Relative humidity frequently exceeds 60%, 
the ideal threshold for mold proliferation. This moisture can 
come from the ground, plumbing leaks, or even humid outdoor 
air.
• Poor Ventilation: Inadequate airflow traps moisture, 
allowing it to condense on cooler surfaces like wood beams 
and insulation.
• Organic Materials: Wood, insulation, and even dust serve 
as food sources for mold once moisture is present.
What Does a Dehumidifier Actually 
Do?
1 2
Removes Excess Moisture Dries Surfaces
By lowering the ambient humidity, dehumidifiers help to 
A dehumidifier pulls humid air over cold coils, 
dry out porous materials like wood, insulation, and 
condensing the water vapor into liquid, which is 
subflooring, making them less hospitable for mold 
then collected or drained away.
spores to activate and grow.
3 4
Prevents New Growth Specialized Units
Maintaining humidity levels below 50-55% effectively Crawl space specific dehumidifiers are designed to 
inhibits the germination of mold spores, preventing operate efficiently in cooler, dirtier environments, often 
new colonies from forming. featuring robust filtration and continuous drainage 
options.
Dehumidifiers Are NOT Mold Remediation Tools
No Killing Power Physical Removal Needed Risk of Recurrence
Dehumidifiers do not possess Effective mold remediation requires Relying solely on dehumidification for 
fungicidal properties; they cannot kill physically removing contaminated an existing mold problem will likely 
mold cells or remove spores. materials and cleaning affected lead to its return once conditions 
surfaces with appropriate solutions. become favorable again.
Crawl Space Encapsulation vs. Dehumidification Alone
Encapsulation: Full Barrier Dehumidification: Air Treatment
• Involves sealing the crawl space entirely with a • Focuses on removing moisture from the air within the 
heavy-duty vapor barrier on the ground and walls. crawl space.
• Blocks moisture from the soil and exterior air • Less effective if continuous moisture sources (like 
from entering. exposed earth) are present.
• Creates a conditioned, semi-conditioned, or • Can be energy-intensive if battling constant moisture 
unvented space. intrusion.
Signs Your Crawl Space Needs Attention
Unpleasant Odors Increased Allergy Symptoms
A distinct musty or earthy smell permeating your If residents experience unexplained sneezing, 
home, often strongest in lower levels, is a classic coughing, watery eyes, skin irritation, or other 
sign of mold or excessive dampness. allergy-like symptoms indoors, mold spores could 
be the culprit.
Visible Mold Growth High Humidity Readings
Look for dark spots, fuzzy patches, or discolored 
areas on wooden structures, insulation, or even Using a hygrometer to measure relative humidity. 
dirt in the crawl space. Mold can appear in various Consistent readings above 50-55% in your crawl 
colors, not just black. space indicate a prime environment for mold and 
potential issues.
Warped or Damaged Wood Pest Infestations
Excessive moisture can cause wooden beams, Many pests, including cockroaches, termites, and 
subflooring, or joists to warp, rot, or show signs rodents, are drawn to damp, dark environments, 
of wood-destroying insects (which are attracted and their presence can signal a moisture problem.
to damp wood).
Best Practices for Mold Prevention 
in Crawl Spaces
Professional Mold Install Vapor Barriers Properly Sized Dehumidifier
Remediation & Encapsulate
Before any other steps, any existing A heavy-duty vapor barrier on the crawl Install a high-efficiency, appropriately 
mold must be professionally and space floor and walls prevents ground sized dehumidifier designed for crawl 
thoroughly removed. This prevents moisture from entering. Full spaces. Ensure it has continuous 
dormant spores from reactivating later. encapsulation completely seals the drainage to avoid manual emptying.
area from the outside.
Regularly Monitor Humidity Address Water Intrusion
Use a reliable hygrometer to continuously monitor humidity Fix any plumbing leaks, ensure proper exterior drainage 
levels. Aim to keep the relative humidity consistently below away from the foundation, and address any other sources of 
50-55%. water entering the crawl space.
REACH US AT
Pure Home
3988 Flowers Road Suite 
670 Atlanta, GA 30360 
(470) 649-3777
[email protected] 
Purehomeus.com