Unfinished basements and below-grade (below the level of the ground) crawl spaces are naturally cool and damp and thus are prone to developing mold-growth problems.
A Dirt Floor
A lot of moisture can evaporate from a dirt floor, which can encourage mold growth on foundation walls, framing elements and stored goods.
Foundation Walls
Even if a crawl space or unfinished basement has a concrete floor, if the space has not been adequately dehumidified during the humid season (generally from mid-April to mid-October), the surface temperature of the concrete may be close to the dew point. Then molds like Aspergillus and Cladosporium species, as well as invisible actinomycetes, will grow on dust settled on the foundation walls.
(Actinomycetes are organisms that produce small spores and grow like mold, but they are actually filamentous bacteria.)
Chronic exposures to actinomycetes, as well as to certain species of Aspergillus mold, can lead to "farmer's lung," a pulmonary disease that is a type of hypersensitivity pneumonitis. "The classic presentation of farmer's lung results from inhalation exposure to thermophilic Actinomyces species and occasionally from exposure to various Aspergillus species," states Laurianne G. Wild, MD, in "Farmer's Lung." "The condition is associated with intense or repeated exposure to biological dusts," she explains (such as dust from moldy hay).
Exposed Fiberglass Insulation in Basements and Crawl Spaces
Mold does not subsist on fiberglass insulation but can subsist on the dust captured in the fiberglass fibers, including sawdust. Then as people walk on the floors above, potentially allergenic mold spores can become airborne and move with airflow to rooms above grade. In addition, mice like to nest in fiberglass insulation, which can result in unpleasant odors.
Prevent Mold Growth
- Dehumidify your unfinished basement and below-grade or partially below-grade crawl space during the humid season. Keep the relative humidity (RH) at or below 50%. Measure the RH with a thermo-hygrometer. Do not depend on an exhaust-only "dehumidifier" to control the RH.
- Keep windows and doors leading to the exterior closed while dehumidifying.
- Don't let anyone saw wood in your basement.
- Your dryer should not vent into the basement or crawl space, because this will introduce a lot of moisture into the space that can support mold growth.
- Cover exposed fiberglass insulation with drywall or with fire retarded sheet plastic. Don't staple into wires, or cover light fixtures.
- Basements and below-grade crawl spaces should never be built with exposed soil. A dirt floor should be covered with heavy-duty vapor-barrier plastic (preferably laminated), attached to the foundation walls, with a treated-wood plank path over the plastic, so people can enter the space. It's best, though, to cover the dirt floor with crushed stone, a vapor barrier and then some type of masonry.
- Have adequate lighting in an unfinished basement and below-grade crawl space, so you can check conditions in these spaces.
Is Mold Already Present?
A musty smell indicates that mold growth is present, but there can also be mold growth without a musty smell. It's difficult to see mold when you shine a flashlight directly on a surface, but if you see small, oval shapes when you shine the flashlight along a plane, you are probably looking at mold growth.
If you think you have mold in your unfinished basement or below-grade crawl space, protect your own health and the health of other members of your family by conferring with an indoor air quality inspector or mold inspector, as well as with a professional mold remediator.
Sources
- Wild, Laurianne G MD and Chang, Eduardo E MD, "Farmer's Lung," Department of Allergy and Clinical Immunology, University of Tulane, New Orleans, LA, emedicine, from WebMD
Resources
- Asthma and Allergy Foundation of America (AAFA), Landover, MD
- Indoor Air Quality Association (IAQA), Rockville, MD
- May, Connie L., "Feathers and Health" Suite 101
- May, Jeffrey C., "Relative Humidity and Mold"and "Basement Mold and Real Estate Transactions," Suite 101
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is worried about his or her health should contact a doctor for advice.
Connie May - Connie L. May is a Certified Indoor Air Quality Technician (CIAQT) based in New England. She and her husband Jeffrey C. May, a Certified ...
