Black attic mold on roof sheathing (C) Daniel FriedmanHow to Find & Test for & Remove Mold in Attics
     

  • ATTIC MOLD - CONTENTS: causes, cures for attic mold contamination. How to prevent mold growth in building attics. Attic mold cleanup procedures. Use of encapsulants on mold in attics; correcting attic ventilation & mosture problems. Investigate attics for hidden mold in insulation or on ceiling materials under insulation.
  • POST a QUESTION or READ FAQs about the causes, risks, and cures for attic or roof cavity mold contamination.
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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.

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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.

Article Series Contents

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.

This article discusses

  • 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?

Photograph: typical mold on attic side of ceiling drywall after a roof leaks -  © Daniel FriedmanIt 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

White attic mold (C) Daniel FriedmanHere 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.

This article is part of our series: MOLD in BUILDINGS which describes how to find mold and test for mold in buildings.

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 INSULATION MOLD TEST where we describe the risk of non-visible problematic mold hidden in building insulation.

 

Continue reading at ATTIC MOLD CAUSES or select a topic from the More Reading links shown below.

Or see MOLD CLEANUP GUIDE- HOW TO GET RID OF MOLD

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