Attic mold is rarely caused by a roof leak. While, yes, occasionally a leak roof is the culprit, condensation is far more likely to cause a mold problem than a roof leak.  Roof leaks tend to flow directly into the living area of the home, allowing for quick identification. The water intrusion is usually dealt with before significant mold growth can occur on the roof sheathing.
Ventilation alone won’t solve the problem. For years I used to just recommend increasing the ventilation throughout the attic space.  But annoyingly, we kept finding houses with great ventilation but persistent mold problems.  A bit more research identified air leakage as the cause.  Think of it this way.  There are two ways to stop condensation and mold growth in an attic.  1.)  we can ventilate and exhaust the warm humid air after it reaches the attic. Or 2.) we can prevent the warm, humid air from reaching the attic in the first place.  This latter approach is far more reliable, and it brings the added benefit of increased energy efficiency.
Attic mold rarely affects the indoor air quality of a building. Because of the stack effect, as warm air rises within a building, particulates and mold spores are continuously moving upward throughout a home. Therefore, mold spores in the attic space cannot enter the home unless these airflow patterns are reversed.  This is only possible under extremely unusual circumstances such as massive ventilation fans or leaky ductwork.  I’ve collected hundreds of air samples in houses with major attic mold problems and never found an elevated count within the home.  (The opposite is true of crawl space mold, where the stack effect can readily bring mold spores into the home.)
Fogging the mold is insufficient. Many mold remediation companies offer a fogging treatment for attic mold.  This involves spraying an extremely fine mist of fungicide on the attic sheathing.  While the technique can be very effective for killing the current mold growth, it does nothing to address the black staining and discoloration that remains. This lingering staining will make the home very difficult to sell in the future; you’ll have a heck of a time explaining to a potential buyer that the mold was treated when it still looks black.
Testing attic mold is rarely called for. Most reputable mold inspectors don’t bother testing attic mold.  A visual inspection is more than sufficient to identify mold growth.  Additionally, the information provided by laboratory sampling will not alter the recommendations.  Whether it’s cladosporium or aspergillus, the solution is the same.
James Mallory – 
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