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Mold Growth Inside Air Ducts
in Greensboro, NC
Mold needs three things to grow: moisture, something to eat, and darkness. Your air ducts provide all three, especially in Greensboro where summer humidity regularly stays above 70 percent for weeks at a stretch. Once mold takes hold inside a duct, every time your system runs it sends spores into every room in the house.
Quick Answer
Mold grows inside ducts when moisture and dust combine in a dark space. In Greensboro, summer humidity regularly sits above 70 percent, and that humid air condenses inside ducts that run through hot attics or unconditioned crawl spaces. A technician needs to remove the mold, find where the moisture is coming from, and fix that source. Do not run the system until the mold is addressed. Call (743) 222-5018 if you smell something musty at your vents.
Telltale Signs
Warning Signs to Watch For
- Musty or earthy smell that gets stronger when the HVAC system runs
- Black, gray, or green spots visible around vent grilles or just inside them
- Household members experiencing unexplained headaches or respiratory irritation
- Condensation or water stains near supply vents on ceilings or walls
- Mold found elsewhere in the home, especially in the crawl space
Root Causes
What Causes Mold Growth Inside Air Ducts?
High Indoor Humidity and Condensation
Greensboro summers bring stretches where outdoor humidity sits above 75 percent for days at a time. When that humid air gets pulled into a duct system cooled by the air conditioner, condensation can form on the inside of the duct walls, especially in flex ducts running through hot attics.
The Fix
Mold Remediation and Humidity Control
Technicians apply an EPA-registered antimicrobial treatment to the duct interior after cleaning out the mold colony. A whole-house dehumidifier or improved attic ventilation addresses the moisture source so mold does not come back.
Crawl Space Moisture Entering the System
Many Greensboro homes built before 1990 have ductwork running through open crawl spaces. Ground moisture in that crawl space evaporates and surrounds the duct exterior. If there are any gaps in the duct joints, that moist air gets pulled directly into the system and feeds mold growth.
The Fix
Duct Sealing and Crawl Space Encapsulation
Sealing the duct joints with mastic stops outside air from entering the system. Encapsulating the crawl space with a vapor barrier cuts off the moisture source at the ground and protects the entire duct system long term.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | High Indoor Humidity and Condensation | Crawl Space Moisture Entering the System |
|---|---|---|
| Musty smell strongest when system runs | ||
| Visible mold at vent grilles | ||
| Condensation on walls near vents | ||
| Mold found in crawl space | ||
| Respiratory symptoms in household members |
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