How to Test For & Detect Mold Contamination in Fiberglass Building Insulation InspectAPedia® -
Where to look for moldy building insulation: conditions, locations, methods
Field Test & Lab Procedures to find mold growth and contamination in building insulation
Testing or inspecting for moldy building insulation or moldy heating or air conditioner duct insulation
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
InspectAPedia.com/appointment.htm.
This document provides information about the testing for the presence of mold growth in fiberglass insulation in residential
and light-commercial buildings. The page top 720x photograph shows a significant presence of Penicillium/Aspergillus type mold spores in our vacuum sample of building insulation that had been exposed to damp conditions..
This website 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.
The photo at left, another sample we collected the interior of mold-suspect insulation shows extensive chains of Penicillium/Aspergillus type mold spores, suggesting that this fungus is probably growing in the insulation itself.
Fiberglass in building insulation is a topic I have been testing and studying since 1986, after having traced building mold concerns to a hidden source in this material.
We frequently find high levels of mold-contaminated fiberglass insulation in buildings which contain other large mold reservoirs.
We have also detected high levels of problematic mold in fiberglass building insulation where other mold reservoirs were either not present or had been previously removed.
Actual Mold Growth in Insulation - Fiberglass insulation can host active mold growth
The presence of both mold spore chains and conidiophores of Aspergillus sp. in the insulation test samples whose photos are shown above confirmed that not only was the crawl space ceiling
fiberglass insulation moldy, but it was supporting active fungal growth.
Our screening samples confirmed that this mold was present in other building areas, most-likely emanating from this mold reservoir of mold-contaminated fiberglass insulation. In some of cases, non-visible mold contamination in fiberglass insulation has been enough to cause IAQ, health, or other mold-related complaints by building occupants, and in some cases
In the partially-opened basement wall shown here at left, the water track stains on the cavity side of the exposed drywall (shown after a test cut was made)
indicate that water passed in this wall from above.
In this circumstance, even when the fiberglass insulation looks clean, I often find high levels of Penicillium sp. or Aspergillus sp. in this material. Comparison tests of fiberglass
which is new at a building supply store or in homes where the insulation has not been wet nor infested with rodents or other pests, mold is rarely a problem.
The photo at above right shows a very dense presence of Pen/Asp spores and spore chains in this insulation test sample.
Where to Look for Mold in Building Insulation
For buildings which do not have other known mold reservoirs, special attention needs to be given to
inspecting and testing for problematic mold in
Wet building insulation: Fiberglass insulation in any building cavity which has been wet - wet once in the past, wet regularly, even if no longer wet.
Insulation exposed to moisture: Fiberglass insulation over wet or damp basements
Insulation in suspect areas: Fiberglass insulation over crawl spaces; fiberglass insulation in areas forming a moisture trap such as insulation between a metal roof and a poly vapor barrier (that is probably imperfect and penetrated, or exposed to leaks)
Insulation in suspect areas: Fiberglass insulation in attics or roof cavities where there has been leakage
Insulation exposed to airborne contaminants: such as mold that was growing on other building surfaces such as drywall, paneling, or cardboard boxes, or insulation that was not protected from or removed from mold remediation or cleanup project areas
Insulation exposed to leaks: Fiberglass insulation in building walls subject to leaks from plumbing failures,previous wetting due to building fire extinguishment, or in freezing climates, walls subject to leaks from ice damming.
Insulation inside or on the exterior of air ducts and HVAC equipment air handlers: Fiberglass heating or cooling duct material, especially if it has been wet from building leaks or A/C condensate mishandling
How to Test Building Insulation for Mold Contamination
We provide the following procedure for testing building insulation for mold for two purposes.
To invite feedback and procedural improvements from other field investigators and building professionals
To provide a simple, inexpensive mold sampling procedure that building owners or occupants of limited financial means can use to get an idea about possible mold contamination in building insulation - a problem area which is often missed by building and mold inspectors.
See INSULATION MOLD for more detailed discussion about the occurrence of mold in building insulation.
Visually Inspect Insulation For Mold First
Before testing apparently "clean" building insulation for mold contamination, look at all of the accessible insulation areas for evidence of visible mold or evidence of leak or water damage that may have wet the insulation.
Tape Sample Visible Mold on Insulation Backing or Kraft Paper
If you see moldy kraft paper backing on building insulation it's reasonable to assume that the insulation is contaminated and that it should be removed, the cavities cleaned, and the cause of mold corrected.
Further mold tests may not be necessary unless needed for medical reasons or for the purpose of comparison with building mold detected in other samples from other areas before or after a building mold cleanup project.
How to Collect Bulk Samples of Insulation to be Tested for Problem Mold Contamination
For people who cannot obtain field services to inspect and vacuum-test building insulation for problem mold, it is possible to cut and remove a square foot of mold-suspect insulation to be sent as a bulk sample to a forensic lab for testing. What we don't like about this approach is that the cost and trouble generally mean that only one or two samples will be collected, reducing our confidence in the conclusion. That is, a lot depends on exactly where and when a mold test sample is collected, and it's a bit too easy to collect a "clean" sample that misses a problem in the building.
If you must collect one or two bulk samples of fiberglass insulation to be tested for mold, we suggest
Collect the sample from the most-suspect area(s) of the insulation, such as areas that are known to have been wet or known to have been exposed to problem locations in a building.
Collect a square foot of insulation, cutting carefully and neatly through the entire insulating blanket, to include the full thickness of the insulation material as well as any plastic, foil, or kraft paper backing on the insulation.
Package the insulation sample in a clean Zip-Lok type plastic bag. It's ok if the insulation is compressed for shipping.
The lab will construct a sterile chamber in which each insulation sample will be agitated and then debris from the insulation will be collected for qualitative analysis.
How to Collect Vacuum Dust Samples of Mold-Suspect Insulation
This procedure prepares dust samples from building insulation for qualitative analysis in a mold lab. (Quantitative analysis by this method would be inaccurate, but it's also unnecessary.)
While some mold inspectors use more sophisticated equipment, the presence or absence of significant problem mold contamination in fiberglass (or other porous) insulation materials, as well as the presence or absence of high levels of other problem particles such as insect allergens, insect fragments (cockroach parts), or even bird dropping contamination can be detected by a competent forensic laboratory from even an amateur-collected insulation sample collected by the process we describe here.
Equipment you'll need to Vacuum-Sample Fiberglass Insulation for Mold
Appropriate protective clothing, gloves, eye cover, respirator, etc. for entering dusty areas.
Air sampling cassettes such as those provided by Zefon Corp. (Air-o-Cel™) or Allergenco™
We have done a long term comparison study comparing these brands, and both work just fine.
A vacuum pumping device that operates in the recommended air-flow range of 10 lpm.
An inexpensive pump that we have tested is the common keyboard vacuum pump sold by Radio Shack™.
While there is some variation in the pump rate of these devices, we found that the pump rate was not excessive (which causes particle bounce and loss in the collection cassette) nor too weak (which fails to collect and adhere particles in the device), and was useable for rough presence-or-absence testing of mold contamination in insulation.
If you already have or can borrow or rent a more sophisticated air sampling pump such as our Burkard Personal Air Sampler or another type calibrated air sampling pump that uses a prepared microscope slide to collect dust particles, and that can be set to the flow rate required by the air sampling cassette, that's great, but it's not necessary for rough presence-or-absence qualitative analysis of building insulation mold. But your pump needs to be portable. Extension cords etc. are not so convenient and can even be unsafe when crawling around in tight crawl spaces or tiny attic kneewall areas.
A plastic tube section about 4" long that will fit into the suction end of the vacuum pump, and onto which an air sampling cassette can be easily attached. (Just take your pump and cassette to a nearby hardware store selling short lengths of clear clean plastic tubing.)
A flashlight to roughly assess the airborne dust level during sampling. Our photos above show a high level of airborne dust in a dark attic in the photo at left, and in the right-hand photo an excessive, overloading level of dust in the same location when we over-agitated the insulation. The amount at left is more than enough debris for a short sample collection interval of a few seconds. Don't overload a dust sample in an air-sampling cassette or it's hard for the lab to make sense of its contents.
Appropriate sample control sheets and paper for writing notes about when, where, how the samples were obtained.
Clean plastic bags or other packaging to mail your samples. Call your mold test lab ahead of time to agree on the price and to discuss the form and type of samples you're sending and the level of analysis you want.
How to Collect Dust Particle Samples from Building Insulation
Here is our procedure. Contact us by email if you have other procedural suggestions or questions.
Select the insulation area to be tested
Prepare your vacuum pump, tube, and mounted cassette so that it's ready to use, but leave it turned off.
Using a screwdriver or pencil, make an opening in the center of the test area that penetrates between 1/2 and 7/8 of the thickness of the insulation.
Using the same probing device as in step 2, agitate the insulation from side to side for 3-10 seconds.
Hold the collection cassette facing the insulation and 1/2" to 6" away from the insulation. If you see that your agitation of the insulation has stirred a visible cloud of dust use the longer distance.
Turn on the vacuum pump for 2-10 seconds, then turn it off.
Check the sample: Remove the air sampling cassette and look into the collection slot in a good light. If the collection slot is loaded with insulation fibers and debris the sample is overloaded and you should try again using a shorter vacuum-on interval and a larger distance from the insulation; don't collect the sample more than 12" from the insulation nor without agitating the insulation at all or you risk sampling airborne particles from another source.
Seal the sample collection end and vacuum end with the adhesive tabs provided so that other debris won't enter the device.
Mail your insulation sample along with the control sheet to a mold test lab or forensic lab of your choice.
Comment on Accuracy of Insulation Vacuum Samples for Mold Testing
This mold sample insulation vacuum approach is not suitable for quantitative analysis such as determining the number of mold spores per cubic foot of material.
But then, our tests have demonstrated that there is already an enormous variation in the absolute level of mold spores pulled from building insulation depending many variables:
The insulation condition, new, old, wet, dry, fiber density
The type of insulation: chopped vs blanket
The extent to which insulation has been covered by other materials or left exposed to water or air
the level of actual contamination,
the mold genera (some species are more easily airborne than others),
the vacuum rate of the pump,
how close the pump is held to the insulation source,
the degree of agitation of the insulation, ranging from "didn't touch it" to "agitated it with a pencil before vacuuming" to "stomped all over it"
But this approach will easily tell you what sort of particles and at what density they are found in an insulation sample, and it's easily the most inexpensive method available for testing building insulation.
What the Mold or Forensic Lab Should Report from an Insulation Mold Sample
The forensic particle identification (or mold test) lab will need to determine the dominant particles in dust collected from the insulation samples and to compare those results with these base points:
New clean fiberglass insulation
Old fiberglass insulation in buildings and common particles found there
High frequency or dominant-particle presence of problematic mold spores, fungal material, or other contaminants. Our photo at left shows a high level of Aspergillus sp. mold spores and our photo near the top of this page shows mold spore chains confirming actual mold growth in mold-contaminated building insulation.
By examining the density of mold obtained from an insulation sample and also by examining the mold qualitatively (such as for the presence of spore chains of Penicillium sp. or Aspergillus sp., a lab should be able to tell you if the insulation is
Generally clean insulation consistent with new material
Mold contaminated by dust and debris exposure
Contaminated with high levels of insect fragments or other possible respiratory irritants
Mold-contaminated with evidence of mold growth or colonization within the insulation.
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Fiberglass building insulation and HVAC duct work insulation hazards
Fiberglass carcinogenicity: Glass Wool Fibers Expert Panel Report, Part B - Recommendation for Listing Status for Glass Wool Fibers and Scientific Justification for the Recommendation", The Report on Carcinogens (RoC) expert panel for glass wool fibers exposures met at the Sheraton Chapel Hill Hotel, Chapel Hill, North Carolina on June 9-10, 2009, to peer review the draft background document on glass wool fibers exposures and make a recommendation for listing status in the 12th Edition of the RoC. The National Institute of Environmental Health Sciences is one of the National Institutes of Health within the U.S. Department of Health and Human Services. The National Toxicology Program is headquartered on the NIEHS campus in Research Triangle Park, NC.
Fiberglass insulation mold: occurrence of mold contamination in fiberglass insulation can be impossible to see with the naked eye, but can be significant
For more information about fiberglass as an indoor air quality concern see:
Mold in Fiberglass, when, why, and how fiberglass becomes a reservoir of problem mold in buildings.
Lab Identification of Fiberglass photographs and text assist in laboratory identification of fiberglass fibers and fragments in air, dust, or material samples in the laboratory using forensic microscopic techniques.
Asbestos: How to find and recognize asbestos in buildings - visual inspection methods, list of common asbestos-containing materials
InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.
The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
InspectAPedia ® Home & Site Map 
Search InspectAPedia
InspectAPedia® Home & Site Map
