Healthy Indoors Magazine
Issue link: https://hi.healthyindoors.com/i/1196895
16 | December 2019 MOISTURE, MOISTURE EVERYWHERE ©2019 Jeffrey C. May in addition, some species of Aspergillus and Penicillium molds can produce mycotoxins. Some species Aspergil- lus can even grow inside the lungs of immune-compro- mised individuals, resulting in an illness called aspergil- losis. Water intrusion: Roof water should not flow down the outside of a building; and chimney flashings are an import- ant deterrent to water intrusion in attics. There are two other conditions that a building pro- fessional should mention to a client: window-cap and door-cap flashings bent toward rather than away from cladding, and wires and cables leading with a down- ward slope into a house. Certain conditions that can lead to water-intrusion below grade include: a building without a gutter system and with inadequate overhang; reverse grading (even from an adjacent property); and a "garage under" with a driveway that slopes toward the house. I'd like to point out three other conditions that concern me: a deck on a house without a gutter overhead; down- spouts that empty into drywells; and concrete patios or walkways next to foundation walls. I've inspected many decks that suffered structural decay due to roof water. And a deck doesn't prevent roof water from ponding next to a foundation wall. Drywells can silt up over time. I recommend that clients stand outside during a heavy rain to see if a drywell is taking downspout water. A great deal of rainwater can flow through cracks in concrete; this water may end up in a basement or crawl space. Internal sources of moisture: Dryers should not vent into crawl spaces. Bathroom exhaust fans should vent to the exterior and not into an attic or soffit. Drop-down stairs or a hatch leading to an attic should be airtight to prevent the upward flow of moist house air; otherwise the moisture can condense on cool sheathing in the fall, winter or spring, leading to mold growth. F ungi require moisture. I want to start with a brief re- view of two types of fungi, because it's important for building professionals to know the difference. Macrofungi produce fruiting bodies that we call mush- rooms or toadstools. These organisms have hyphae that can fan out a few feet to many yards (or in some cases across acres of soil) from the location of the mushroom. The hyphae can be visible or more often, can be present within the substrate. Macrofungi are wood-decaying organ- isms, and most do not grow in temperatures below 55 o F. Microfungi, commonly called "mold," grow in colonies and fan out along a surface. These organisms subsist on biodegradable surface materials that include dust, oils, fats, starches, wood sugars, pet-dander particles, and skin scales. While most microfungi do not degrade wood, they produce large numbers of spores that can impact human health. Both kinds of fungi require moisture, but macrofun- gi need more moisture than most species of microfungi need. Some molds (microfungi) such as Aspergillus and Penicillium can flourish in conditions of elevated relative humidity (RH) without the presence of liquid water. Exceptions would be Stachybotrys mold, commonly known as "toxic black mold," and Chaetomium mold; both need chronically damp conditions. Stachybotrys and Chaetomium molds commonly grow on the paper of wet drywall and not the plaster. Both of these fungi are black, so some people mistake one for the other. Clad- osporium mold is also black but can grow under drier conditions. This type of mold is commonly found on attic sheathing and on basement foundations. I am more concerned about the presence of Aspergil- lus and Penicillium molds than I am about the presence of Stachybotrys mold, because Aspergillus and Penicillium spores are more readily aerosolized than Stachybotrys spores are. Thus exposures by inhalation are more likely;