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This document gives advice on how to find, test for, and remove mold in building attics and roof cavities. This is a chapter of "How to Look for Mold" 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 discuss the risk of non-visible problematic mold hidden in building insulation.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links 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.

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

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:

1. 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.
2. 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.

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• Additional technical contributors & reference sources for this article are listed below.
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.

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.

FIND MOLD in BUILDINGS, HOW TO
  ATTIC MOLD
    ATTIC MOLD CAUSES
    ATTIC MOLD IS A PROBLEM ?
    ATTIC MOLD - IS IT TOXIC?
    ATTIC MOLD, WHERE TO LOOK
    ATTIC MOLD, WHAT IT LOOKS LIKE
    ATTIC MOLD, HARMLESS COSMETIC?
    ATTIC MOLD ROOF TEAROFF
    ATTIC MOLD ENCAPSULANTS
  BATHROOM MOLD
  BASEMENT MOLD
  BASEMENT MOLD WATER IMPACT
  BLACK MOLD, HARMLESS COSMETIC
  CARPET MOLD CONTAMINATION
  CARPET TEST GUIDE
  CRAWLSPACE MOLD
  DRYWALL MOLD
  DIRT FLOOR MOLD CONTAMINATION
  ESSENTIAL STEPS IN FINDING MOLD
  FLASHLIGHT HELPS FIND MOLD
  WHAT MOLD LOOKS LIKE
  Black Mold  Brown Mold
  Green Mold  Red Mold
  Yellow Mold  White Mold
  Invisible Mold
  Meruliporia Mold Photographs
  Mildew Photographs
  Recognize Cosmetic Mold
  Recognize Harmless Black Mold
  Stuff that is Mistaken for Mold
  HIDDEN MOLD, HOW TO FIND
  Photo Guide to Finding Hidden Mold
  Hidden Mold Behind Paneling
  Hidden Mold Between Framing & Sheathing
  Hidden Mold in Flooring & Subflooring
  Hidden Mold in Wall Cavities
  Spotting Hard-to-See Mold
  Use of a flashlight to find mold
  Wall test cuts to spot hidden mold
  Light colored toxic molds
  Moisture Gradients and Mold
  Other Places to Look for Hidden Mold
  INSULATION MOLD
  SAMPLE POINT CHOICES FOR MOLD TEST
  SAMPLING MISTAKES
  USING LIGHT TO FIND MOLD
FLOODS & MOLD CLEAN/PREVENT
MOLD ACTION GUIDE - WHAT TO DO
MOLD EXPERT, WHEN TO HIRE
MOLD RELATED ILLNESS
PREVENT MOLD, HOW TO
MOLD DETECTION & INSPECTION
MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
MOLD APPEARANCE - STUFF THAT IS NOT MOLD

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

• Books, Complete List of Environmental Inspection, Diagnosis, Cleanup, Air Quality & Design, Inspection, Repair Books at the InspectAPedia Bookstore
• Environmental Health & Investigation Bibliography - our own technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
• Mold and Allergen Recognition and Identification - Not All "Black Mold" is Harmful; Some Suspect Stuff is Not Mold
  • How to Find and Test For Mold in Buildings - Looking for Mold - A 'how to' photo and text primer on finding and testing for mold in buildings
  • Recognizing Mold: What mold looks like mold identification photos to help identify mold - choosing what to sample in buildings
  • Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
  • Stuff that is not mold but is often mistaken for it - things you may not want to test. Also, not all "black mold" is toxic - here are examples of harmless black mold.
  • Mold Action Guide: an easy step by step outline of what to do about mold
  • How to find mold without hiring anyone, for do-it-yourself'ers
  • Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
  • Mold Test Kits - How to Collect and Send Your Own Mold Sample to our mold testing lab
  • How to find a mold inspector or test consultant: Directory of IAQ,Sick Building, Mold Allergen Testing, Building Investigation Service Providers
  • Meruliporia: the house eating fungus or "poria"
  • Mold Investigation Tips for Home Inspectors how to find mold, where to look, what is likely to be important. Advice to building inspectors intending to inspect or test for toxic or problematic mold indoors, mold inspection methods, and mold test methods which are valid or invalid
  • Mold Risk Levels in Buildings Based on Visual Inspection - simple visual clues help decide on action
  • Mold in Fiberglass Insulation© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation - DJF
  • Frequently Asked Questions About Mold -- check this FAQ list & IAQ Site Map to see if you can find a quick answer to your mold concern
  • When to hire a professional to inspect for toxic mold or other allergens
• ...

More Information on Building Diagnostic Inspections and Repairs

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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

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

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.

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