• Disconnected at the bath fan (most common with older fans)
  • Partially disconnected at the roof junction (not very common)
  • Directed at soffit vents instead of dedicated roof vent: These are never very tight connections and soffits are already prone to mold

 Common ATTIC DUCTING ​POINTS of​ Failure   

  • Faulty  supply ducts
  • Faulty cold air return
  • Using ducting intended for clothes dryers (ABSOLUTELY NOT RECCOMENDED)

Ducting & Mold

 Less Common attic DUCTING ​POINTS of​ Failure   

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Serving South East Idaho city's such as Rexburg, Idaho Falls, Blackfoot, Pocatello & Jackson Hole Wyoming as your premier mold removal specialist, indoor air quality (IAQ) expert and home mold remediation services provider

Getting straight to the point, mold won't grow in your ducts. However, you ducting can cause mold to grow if it gets disconnected, is improperly installed, broken or faulty they can cause all kinds of mold issues.

Disconnected, broken and improperly installed ducts are a major cause of mold growth on attic sheathing. The reason is simple; if an exhaust duct, such as a bathroom vent, is disconnected, all the warm, humid air from the house is pumped directly into the attic.  This moisture condenses on the cool roof sheathing and eventually causes mold growth and sheathing failure.  If the problem is severe and the attic has a compounding problem, such as poor ventilation, the moisture buildup can occur throughout the entire attic assembly.  This often occurs in houses with poor passive ventilation in the roof.  


In some cases, you will experience "Focused mold and moisture".  In many cases, the faulty ducting effects only the area immediately surrounding the disconnected duct.  Both moisture and mold growth will be limited to approximately a 5-10 sqft. area above the defective ducting.

Jeffrey Parsons

2300 North Yellowstone Highway, Idaho Falls, ID, United States

Office: (208) 535-3289

Cell: (208) 360-7892 

Email: jeffp@hhepro.com