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Mold in the Attic

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Attic Mold - A Common Phenomenon

Mold growth occurring in the attic is one of the most common locations for mold growth. In cooler climates mold can often be found on the underside of the roof sheathing and the adjacent framing.  Hot climates with heavy A/C usage suffer from the opposite issue, with mold growth occurring on the topside of the ceiling. 

Is attic mold a health problem?

Fortunately, mold growth in the attic is typically not a health concern.  This is due to the air flow patterns within a home; specifically, the stack effect, which causes warm air to rise from the lowest section of the house to the upper floors and eventually up and out the attic.  Because of this, attic mold growth rarely is found in the indoor air environment of the home.  However, attic mold can cause substantial structural damage and should still undergo professional mold remediation.

Severe Attic Mold

Severe Attic Mold

What are the most common mold problems associated with attics?

How is attic mold prevented?

Preventing attic mold requires the elimination of excess heat and moisture.  Why? Because the food source cannot be removed, and even the most expensive mold preventative coatings will eventually fail.  Therefore, we must tackle the underlying moisture issue.   

Removing attic moisture is difficult because of the number of variables involved. Soffit ventilation, ridge venting, air leakage through the ceiling, can lights and penetrations, etc. can all contribute to a failed attic assembly.  Reducing moisture in an attic can be complicated and is best left to a professional mold inspector.

A good mold inspector will evaluate the following variables that contribute to attic mold:

  • Measure current soffit ventilation
  • Measure ridge or gable ventilation
  • Calculate required ventilation.
  • Identify blocked venting
  • Identify disconnected exhaust ducting.
  • Identify air leakage points
  • Identify cold air return.
  • Measure insulation level throughout attic.


Example Inspection Report Involving Attic Mold

Work #: 201005

Attic Sheathing Mold

Mold Growth:

  • Inspection of attic revealed mild to moderate mold growth throughout significant areas of attic sheathing.  At this time, the mold growth has not lead to significant structural damage of the underlying materials. However, because the home is new construction, the mold growth is a result of the attic sheathing being exposed to the weather prior to getting the roof membrane on.  The wet attic sheathing was not able to dry fast enough to prevent mold growth from occurring.


  • Elevated moisture noted throughout significant portions of the attic sheathing.  It is necessary to thoroughly dry the framing and sheathing prior to the application of encapsulant.
  • Moisture content readings of the attic sheathing ranged between 25% and 75% depending on the location sampled.
  • It is necessary to have consistent moisture content readings of below 20% prior to any remediation.    


Mold in Attic
  • No obvious roof leaks were observed on inspection of the attic.  Environix is not a professional roofing contractor and cannot guarantee the condition of any roofing structure.


  • Insulation shows no signs of significant water damage, or mold growth.  Spores may be present in the insulation, and it can be removed at the customer’s request, but once the recommended steps are performed the spores are unlikely to negatively impact indoor air quality.


  • Current ventilation is adequate to exhaust normal amounts of humidity.
  • Several locations were present where a pony wall was installed and blocked the natural airflow between the soffits and the ridge.  Areas with blocking should have similarly sized holes drilled as the lower soffit venting.
  • Proper ventilation is necessary to minimize condensation and subsequent mold growth.  All areas of elevated moisture or improper ventilation must be addressed to ensure the effectiveness of our process.  Current code calls for 1sqft of ventilation for every 300 square feet of attic space, distributed evenly between the ridge and soffit area. 
  • Builder must ensure adequate ventilation is present in the vaulted section of ceiling above the living room area.  A minimum of 2 inches of air gap must be present between the insulation and the attic sheathing.  In addition, it is imperative that ridge and soffit venting is present for each ceiling joist bay. 
Attic Mold

Air Seal:

  • The ceiling currently lacks proper air sealing, allowing excess moisture and heat to escape into the attic area.  This air leakage is a key cause of energy loss, attic condensation and mold growth. 


  • The attic contains HVAC ducting which appears to be adequately sealed.
  • It is necessary that the HVAC unit be masked prior to the remediation to prevent overspray from landing on the HVAC unit.

Other Contamination:

  • No evidence of past or present rodent infestation was noted.

Trash and debris:

  • The attic is currently free from excessive amounts of trash and construction debris.
  • Attic Mold photo
    Mold growth - spotting on attic sheathing
  • Dark Staining from attic mold growth
    Staining from black mold on attic sheathing