How to Find & Test for & Remove Mold in Attics

How to evaluate the risk of toxic (or harmless) attic mold
Where to look for mold in a building attic
When is it necessary to tear off a roof to deal with attic mold?
When to use or not use media blast and use encapsulants for attic mold
Should attic mold even be removed? Are there other more important mold reservoirs to clean up first?
Which insulation is most or least likely to harbor non-visible mold
How can moldy air move downwards from an attic into occupied building space?
Questions & Answers about the causes, risks, and cures for attic or roof cavity mold contamination.
References

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Attic & roof mold: this article series on attic and roof mold contamination gives detailed step by step procedures and advice on how to find, test for, remove & prevent future mold contamination in building attics and roof cavities.

This article is part of our series: FIND MOLD in buildings, HOW TO which describes how to find mold and test for mold in buildings, including how and where to collect mold samples using adhesive tape - an easy, inexpensive, low-tech but very effective mold testing method. This procedure helps identify the presence of or locate the probable sources of mold reservoirs in buildings, and helps decide which of these need more invasive, exhaustive inspection and testing.

Readers of this article series about black, white, green and other colored mold on attic and under-roof surfaces should also be sure to read ATTIC MOLD CAUSES and also see INSULATION MOLD where we describe the risk of non-visible problematic mold hidden in building insulation.

IS ATTIC MOLD A PROBLEM ? - Is attic mold a health risk or indoor air quality problem?

Photograph: toxic mold on pine tongue and groove roof sheathing - © Daniel Friedman

Toxic attic mold: The photo at the left was identified as a toxic mold that probably should be removed, although the ease of movement of mold spores from an attic down into a living area varies widely from building to building.

Uncertain attic mold: The photo at the very top of this page shows where you may find mold growing on the attic side of ceiling drywall, particularly below roof leaks or in areas of ice dam leaks at a building eaves.

We pulled back the fiberglass insulation to expose this small area of mold growth. What about the white mold-suspect material observed on the rafters? Is that mold? If so is it a problem?

The answer is, "it depends." In addition to testing to see what this material is (presuming there is a large area of it), we'd also evaluate the chances of particle movement between the attic and the living space before deciding on an appropriate approach to this moldy attic.

It is simply not the case that all attic mold is toxic. It is not the case that all attic mold is harmful.It is not the case that all attic mold needs to be cleaned or removed. It is not the case that all attic mold is going to enter the living area or otherwise be a problem for building occupants.

It is however the case that attic mold indicates damp conditions or leaks and therefore some further investigation or thought are in order.

Be sure to use the links at the left of this page to review other examples of mold found in attics on tongue-and-groove roof sheathing, brown mold and very dark brown, black-looking mold on attic plywood, and the risk of hidden mold in attic insulation.

See ATTIC MOLD, WHERE TO LOOK then ATTIC MOLD, WHAT IT LOOKS LIKE and also WHAT MOLD LOOKS LIKE.

Also see our photo guide to finding attic moisture and mold at How to Inspect Attics for Condensation & Moisture - to Detect & Correct Attic Condensation, Frost, Ice Dam Leaks & Attic Mold

RISK OF TOXIC ATTIC MOLD - How to Evaluate the Risk of Toxic Attic Mold

Here are some comments about air and particle movement in buildings and thus the chances that attic mold will be transported from that area into the living space.

Air and particle movement in buildings tends to be up and out from lower floors to upper floors to attic.
There is not such easy particle movement downwards from an attic into a building.
Attic mold is less likely to be the significant mold problem source in a building than moldy lower areas such as basements, crawl spaces, or wet building cavities.
Important exceptions to this normally-upwards movement of indoor air currents do occur however:
- Attic or whole house fans: When a whole house vent fan is used and the attic venting is inadequate - resulting in a pressurized attic. When the fan is operated, attic particulates, including mold, insect allergens, rodent fecal debris, mite fecals, bird droppings, dust, particles (Histoplasmosis risk), may be blown downwards into the living area or into attic-mounted HVAC equipment.
- Moldy attic knee wall areas: A moldy attic kneewall space adjacent to a bedroom on the upper floor of a cape cod or similar house.
- Pine roof sheathing: Older homes using pine boards as roof sheathing use a material which more readily supports growth of Aspergillus sp. and Trichoderma viride as well as other more problematic than I find in plywood-sheathed roofs.

Is Mold Sealed-Up in Building Cavities Hazardous?

When attic (or other building) surfaces or insulation contain a large reservoir of toxic or allergenic mold, AND if the area were inaccessible, say because the space is too small to enter, then it may be necessary to remove some portion of roofing to give access for remediation, particularly if there is evidence of transmission of problem mold from that space into the living area.

While some experts (Burge et als.) have opined that there is no important toxic mold spore movement from these "almost sealed" building cavities into occupied space, and thus that mold in building cavities is not a problem, our direct field inspection and test results, as well as client interviews and live field tests performed with clients have demonstrated that that assumption is not reliable, and that in at least some buildings, certain easily airborne mold genera/species such as Aspergillus sp. may move throughout the structure and may be a health concern for some building occupants.

The movement of mold-spore laden air in and out of building cavities and between building areas is not reliably predicable from a visual inspection, nor from simple air tests.

Simply turning a building fan on or off, opening or closing a window, turning up the thermostat, and many other conditions can change how air is moving in buildings.

Air Does Not Always Move Up and Out of a Structure as Building Science Would Suggest

Finally, building air sometimes moves contrary to what building science would lead us to expect. For example we assume that warm air rises up through buildings, passing out through roof ventilation. But direct measurement in some buildings has shown that warm air (including from a moldy attic) can sometimes flow downwards into the occupied space. Two examples that we have frequently observed in the field:

Air conditioning the upper floors of a hot building can cause a sufficient volume of chilled air to flow downwards (by gravity, through stairwells) at a rate that draws warm air down into the occupied space from an attic.
Use of a ceiling-mounted whole house fan to attempt to exhaust hot building air, combined with inadequate exit ventilation out through the attic or roof space can pressurize the building attic, blowing attic air (possibly warm or moldy) downwards into some building areas, air passing through openings cut for ceiling light fixtures, wiring, plumbing, or duct work.

Frequently Asked Questions (FAQs)

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Technical Reviewers & References

Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: johncranor@verizon.net
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.

Related Topics, found near the top of this page suggest articles closely related to this one.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

Mold Contamination Testing, Cleanup, Prevention: references & products

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
Aerobiology, Building Science, Microscopy, & Laboratory References, an extensive technical bibliography
Allergens: what they look like in buildings
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
Clinical Mold References - Detailed bibliography of mold reference texts
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens," Patricia Donald, Department of Plant Microbiology and Pathology, Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
"Management of Powdery Mildew, Leveillula taurica, in Greenhouse Peppers," Ministry of Agriculture and Lands, British Columbia - Original source: www.agf.gov.bc.ca/cropprot/peppermildew.htm
Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Fiberglass: Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
Looking for Mold Procedure: what mold is often found where in buildings - simple technical presentation
Meruliporia: the house eating fungus or "poria"
Mold Action Guide: Step-by-Step Instructions, What to do about mold, mildew, and other indoor allergens
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE Photos of what mold looks like in buildings
MOLD APPEARANCE - STUFF THAT IS NOT MOLD Photos of NOT-mold material that is sometimes mistaken for mold
MOLD ATLAS & PARTICLES INDEX, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
MOLD BY MICROSCOPE Mold under the microscope - photo identification of the most common indoor molds found in buildings
Mold FAQs Answers to Most Questions about Indoor Mold, Mold Related Illness, Mold Cleanup, Mold Prevention
US EPA: Mold Remediation in Schools and Commercial Building [Copy on file at /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
Mold spores in the Home - a Photo ID Library for detection and identification of mold allergens
Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab or to any mold lab you wish
Most Common Indoor Molds Found in buildings, A Table of
Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Rot concerns in buildings-some building mold such as Meruliporia incrassata "Poria" risks serious rot and hidden structural damage
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol

OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold

Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.

Fiberglass building insulation and HVAC duct work insulation hazards
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Other environmental risks: Asbestos, carbon monoxide, electromagnetic fields, environmental illness, fiberglass, MCS - multiple chemical sensitivity, toxic gases, etc
Indoor Gas Sampling Plan for Residential buildings lists a number of toxic indoor gases which we test for, depending on the building complaint and building conditions
Ozone Warnings - Use of Ozone as a "mold" remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings, and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some help from a licensed pest control expert.
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