Photograph of crawl space insulation which testing found to be mold contaminated.When to Test for Mold in Building Insulation

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When should you test building insulation for mold contamination?

This document explains when and why it is appropriate to test for mold contamination or actual mold growth in certain insulation in residential and light-commercial buildings.

This article series discusses health hazards associated with moldy fiberglass in buildings, with focus on fiberglass insulation, fiberglass fragments, fiberglass in heating and air conditioning duct work, and invisible but toxic mold growth in fiberglass which has been wet, exposed to high humidity, or exposed to other moldy conditions.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

When to test building insulation for mold

Fiberglass insulation © D Friedman at For cost and ethical reasons, we do not recommend testing building insulation for mold as a regular procedure.

That is because by no means is it always appropriate or justified to test building materials for mold.

Insulation that has been properly installed, not subjected to water leaks, and not subjected to contamination from external sources such as an improperly-conducted mold remediation job should be fine. (Photo at left).

But sometimes it's a good idea. This article explains how to find or test for moldy insulation in buildings, the probable cause of mold contamination in building insulation, and how to recognize conditions that make that problem likely in a particular case.

We would recommend inspecting and testing building insulation for mold in the following cases:

insulation contaminated in a crawl space

Photograph of extensive basement Stachybotrys chartarum contamination - © Daniel Friedman

When Not to Test Building Insulation for Mold

Memnoniella echinata mold contamination (C) Daniel Friedman

Visible evidence of extensive mold contamination may already indicate that insulation needs to be replaced: Insulation that obviously needs to be replaced because it has been in contact with or exposed to heavy mold contamination such as the Memnoniella echinata - contaminated wall cavity in this New York City apartment does not need to be tested. It needs to be replaced.

Exception: for medical reasons such as to provide possibly helpful environmental information to a treating physician, we may test a building or building materials to identify contaminants.

Furthermore if insulation has been soaked from a building leak or fire extinguishment, it should be replaced regardless, and testing is probably not necessary.

Non-suspect low-risk cases of fiberglass insulation: we do not recommend routine testing of building fiberglass for mold in non-suspect cases such as where insulation is new and/or has not been exposed to water, dampness, or other mold contamination sources.

"Spot checks" by "mold testing" in buildings, if conducted without an expert diagnostic visual inspection and history gathering, are simply not reliable and thus not cost-justified.

Other building insulation materials that are not conducive to mold growth: such as

are unlikely to be mold-contaminated but might need to be replaced anyway if damaged or soaked.

Watch out: leaving wet building insulation in place during a restoration project is asking for a future mold contamination issue in the building.

Low-risk buildings where there are no building-related occupant health or air quality complaints: 

See MOLD / ENVIRONMENTAL EXPERT, HIRE ? for more detailed advice on deciding when it is appropriate to hire a professional or to perform further mold testing in a building.


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