The Mold Albatross
Mold! Buyers are frantic about it, sellers are frightened of it, and people are looking for someone to pay the cleanup bill. So it makes sense that home inspectors are leery of mold. However, understanding more about this indoor contaminant can reduce the home inspector’s liability.
Black attic sheathing
In parts of the country where nights are cold, black mildew on sheathing is common, particularly on the north-facing gable. The most often sited cause of attic mold is inadequate ventilation, but this is not correct. The true cause of the high relative humidity and condensation that can lead to mold growth is the presence of excess moisture. In some homes, no matter how much attic ventilation is present (mildew problems even occur on cathedral ceilings of screen porches!), excess moisture infiltrating from the house into the attic will lead to condensation. Solving attic mold problems means eliminating the sources of warm moist air: pull-down stairways, plumbing chases, openings around chimneys, and blowers that exhaust into the attic. Even bathroom vents that exhaust through hoses that terminate in the soffit space rather than at the exterior are a large source of moisture. These installations are common and should not be overlooked.
And unfortunately, many attics are ventilated after the fact. Very often openings are not cut in the sheathing for ridge vents, or the vent that is installed is so inefficient (due to the inert materials present to reduce water and snow infiltration) that it is useless, even with appropriately sized sheathing cut-outs.
Microfungi and macrofungi
The usual mold growth on sheathing does not necessarily lead to the widespread destruction of the wood structure. The mold on sheathing is generally referred to as “microfungi” (mildew-type), rather than “macrofungi.” Macrofungi are wood-destroying organisms that produce visible fruiting bodies such as toadstools and mushrooms. Macrofungi need constantly wet conditions, such as sheathing in an insulated wall or ceiling cavity saturated with water from a leak. Most attic molds are mildew-type fungi, few of which destroy wood the way the wood-decay fungi do.
The spores from microfungi such as Aspergillus, Penicillium, and Stachybotrys are most often responsible for allergic reactions associated with indoor air quality problems. Aspergillus and Penicillium spores are commonly found in air samples taken from contaminated spaces, but Stachybotrys spores are rarely airborne for long, because they are larger, produced in clumps, and tend to settle out of the air more quickly. There is widespread fear that attic molds will lead to contamination of house air, but this is usually not the case, because the molds that grow on sheathing are not very friable, nor are they often disturbed.
Basements
Microfungal growth, commonly observed on basement surfaces such as panel, drywall, and even furniture, is most often a sign of excess humidity and not leaks. On solid surfaces, such as finished wood, or metal or tile, microfungi can easily be washed off, using appropriate personal and environmental controls. Where there are microfungi growing on wallpaper, or on fleecy surfaces such as cushions or mattresses, the items have to be discarded. Much overlooked potential sources of musty odors as well as spore exposures (even to toxic spores) are the unfinished bottoms and backs of antiques such as dressers and tables that have been stored in basements or damp garages. Such mildew growth is readily visible when observed with a mirror and a bright flashlight. On solid unfinished surfaces, this type of mildew can be cleaned outdoors (and again, using appropriate personal protection) and surfaces coated lightly with shellac in order to seal in residual spores. Regrowth will not occur as long as the piece is not exposed to long periods of high relative humidity.444
Mechanicals
The largest source of health symptoms in buildings is mold and other microbial growth in air conditioning equipment and hot air furnaces. In nearly all air conditioning and heat pumps, microbial growth can be present, both on the coil and in the condensate pan. (Microbial growth on coils and in fiberglass lining material is responsible for the sweat-sock odor nearly always present when air conditioning is initially turned on.)
Carpeting and walls
The other major source of indoor microbial problems is carpeting that has been subjected to moisture, either from leaks or excess relative humidity. In finished, below-grade spaces that are not dehumidified, nearly all basements carpets (in homes) are contaminated with mold growth. Since the growth is usually concealed and is growing in aerosolizable dust, exposures can be very significant.
The discoloration on drywall, or paper or ceiling materials from a leak does not necessarily contain mold or bacteria. Stains really have to be tested to see if they contain microbial growth. If stain surfaces dry out fast enough, they are not likely to become moldy.
Black ghosts and white fuzz
Soot from burning jar candles is frequently mistaken by homeowners (and even some testing labs) as “toxic black mold.” One family was told to evacuate their house because of soot stains incorrectly identified as “toxic” Stachybotrys chartarum. Efflorescence consists of minerals and is harmless, yet another family was told to flee their home by a remediator who was more than happy to charge them $3,000 to wash the efflorescence off their foundation as they waited nervously in a hotel room.
Fungal growth threatens us all, not only because it can creep along unseen, but also because, whether visible or not, mold can grow within 24 to 48 hours if the conditions are right. A room that is mold free during a home inspection can be full of mold a week later. We ASHI inspectors don’t want to get caught in the middle (or in front) of mold litigation, and knowledge about mold—why, where, and how it grows—can sometimes be the only tool that removes the mold-albatross from the ASHI inspector’s neck.
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