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Can clean-looking insulation be moldy? This document provides information about the occurrence of problematic toxic or allergenic mold growth in fiberglass insulation that appears, on visual inspection, to be clean in residential and light-commercial buildings. A 720x micro-photograph provided in this article shows active fungal growth along the surface of a fiberglass insulation fiber collected the suspended ceiling of a building suffering wet conditions and moldy in-slab HVAC ducts.
Mold is often found in basement fiberglass insulation, crawl space fiberglass insulation, fiberglass wall insulation, heating or cooling duct fiberglass insulation, and attic or roof insulation in buildings which have either been wet or have been exposed to high levels of mold from other sources.
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The fiberglass insulation falling into a crawl space at the left hand photo above is obviously suspect for having been wet and possibly contaminated by rodents, insects, or toxic or allergenic mold.
But what about the nice new clean looking fiberglass insulation in the right hand photo.That clean-looking fiberglass insulation was located over a clean-looking basement of a home less than ten years old. But a closer inspection of the home, its exterior, and its basement (as well as attic) found several clues suggesting that during one or more prior springs the basement had been quite wet. Check our our Mold-Contaminated building insulation photo just below.
Mold-Contaminated building insulation: But testing the clean looking yellow fiberglass in the photo show n earlier on this page disclosed the remarkably mold contamination shown in our photograph at left.
Special vacuum and agitation methods are needed to sample and test this material and special care is needed in choosing the sample or test location when looking for mold in fiberglass or other building insulation.
What can be tricky in investigations of mold contamination in building insulation is that severely mold-contaminated fiberglass insulation may look pretty clean to the naked eye
The photo at above left shows clean looking insulation; in fact this is one of our baseline samples of clean fiberglass insulation fragments (taken from a sample of new fiberglass building insulation).
The photo at above right shows dirty looking insulation from an older building. The right photo of a sample collected from fiberglass insulation in an older building exposed to moisture and leaks shows a high level of particulate debris, almost certainly including organic debris such as skin cells, animal hair, and insect fragments which can form a base for mold growth. But we didn't detect problematic mold in either of these cases.
Of course a high level of insect fragments, mite fecals, or rodent fecal and urine-contaminants in any building insulation can result in indoor air quality complaints if air and dust move from that particle reservoir into the living area.
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Questions & answers or comments about mold contamination in fiberglass insulation that looks "clean" - where can the mold trouble come from? How is it detected? What should be done about moldy insulation? Are all insulation materials equally prone to hosting mold growth?.
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Technical Reviewers & References
Fiberglass in buildings: hazards, testing, cleanup, prevention: references & products
For more information about fiberglass as an indoor air quality concern see: