TECHNICAL #1504 RESOURCE SHEET Frequently Asked Questions About Mold The presence of unwanted or excessive moisture in buildings can lead to structural performance problems, as well as concerns about possible health risks. One area of concern is mold and mildew growth. Homeowners, builders, and contractors can benefit from having accurate, fact-based information on mold, mildew, and wood decay fungi. Q: What is mold? is often presented by the media as the A: Mold and/or mildew are microscopic fungi main driving force for the current increase that are present virtually everywhere, in moisture/mold claims. However, mold indoors and outdoors. They grow on a needs moisture to grow and moisture can variety of organic materials, including wood come from multiple sources in a house, products(1)(2). many of which have nothing to do with the amount of fresh air exchange a building Q: How do molds enter an indoor experiences. A leaky foundation wall or environment and how do they grow? a chronic plumbing leak releasing water A: Molds may be present in outdoor or indoor onto drywall are two examples. There can air. Mold spores from the outside may be cases where the humidity level in a enter a house through open doorways and house would be lower with more fresh air, windows, or though heating, ventilation, potentially alleviating some moisture/mold and air-conditioning systems. Spores in problems, but to characterize this as the the outside air also attach themselves root cause of mold problems is incorrect(6). to people and animals, making clothing, shoes, bags, and pets convenient vehicles Q: Why is mold a concern? for carrying mold indoors(3). A: Mold and/or mildew fungi do not cause Unlike decay-producing fungi, decay; however, the environment that mold and mildew alone do not Mold needs oxygen, water, nutrients, and a fosters mold growth will also support cause significant loss in the temperature between 40 degrees and 100 decay-producing organisms(10). Addition- strength of wood products. degrees Fahrenheit to grow(4). Mold spores ally, mold produces spores, which often can grow when they come into contact with become airborne and may create allergic a food source where there is excessive reactions in some people(4). moisture, such as where there are leaks in roofs, pipes, walls, or plant pots, or where Q: A house has a water leak. What is there has been flooding. Additionally, an the potential for growing mold in the average relative humidity of 80% or more leak area? over a month's duration will provide suf- A: Materials that are exposed to a constant ficient moisture for mold growth(5). Many leak or have been soaked and not dried organic materials (e.g., wet cellulose mate- thoroughly can support mold growth. Some rials, including paper and paper products, molds can form a new colony in one or cardboard, ceiling tiles, wood, and wood two days on damp materials. Molds do products) provide suitable nutrients to sup- not require light and can continue growing port mold growth. Inorganic materials such indefinitely without light(7). as dust, paints, wallpaper, insulation mate- rials, drywall, carpet, fabric, and upholstery Q: What about moisture in the crawl space? can also support mold growth(3). A: There is no definitive answer regarding moisture problems in the crawl space. Q: Is mold occurring because buildings are A symposium on the subject held by the now "air tight"? American Society of Heating, Refrigeration, A: This rationale for moisture/mold problems and Air-Conditioning Engineers produced Frequently Asked Questions About Mold the following recommendations(8): to check a building's compliance with taken in a unique situation cannot be • There should be proper drainage, federal mold standards(1). Testing for mold interpreted without physical inspection clearance, and access. is also difficult because mold is every- of the contaminated area or without • Crawl spaces should have ground covers where, and therefore, testing will not prove considering the building's characteristics for moisture control. These should be in- that a house is free of mold(6). The U.S. and the factors that led to the present stalled to limit evaporation from the soil. Centers for Disease Control and Prevention condition(3). • Heated crawl spaces should not be (CDC) advises that it is not practical to test vented with outdoor air. for mold growth in a house because large Q: How do you determine whether a mold • Unheated crawl spaces may be vented, mold infestations can usually be seen is "toxic"? but there is no overriding need to do or smelled(3). When testing is done, it is A: Unfortunately, it is impossible for home- so for reasons of moisture control if usually to compare levels of mold spores owners to distinguish between so-called an effective ground cover is present. inside the house with levels outside the "toxic" and "non-toxic" molds because they (Note: check with local building codes to house(7). all look like black or gray sooty patches. verify whether this practice is permitted Press coverage about lawsuits and health in your jurisdiction.) A thorough inspection of a house, to check studies involving mold has focused on for signs of moisture problems or active one type of mold called Stachybotrys Q: With wood, at what moisture content mold growth, is likely to be more effective chartarum, which is often referred to as does mold become a concern? than testing as a way to size up potential "the toxic mold." However, there is no A: A moisture content greater than 19% is problems(6). It is usually not necessary to particular reason why this mold should be sufficient to support mold growth. This identify the species of mold growing in a singled out, as all molds should be treated moisture content is also sufficient to sup- residence, and CDC does not recommend with caution(4). port decay-producing organisms(9), which, routine sampling for molds. unlike mold, can cause permanent loss of Q: What is Stachybotrys chartarum structural strength(10). Wood can achieve Current evidence indicates that allergies (Stachybotrys atra) and what should this moisture content when exposed to are the health problems most often people do if they determine it is present direct wetting from any source of moisture, associated with molds, and because the in their buildings or homes? or from extended exposure to an appro- susceptibility of individuals varies greatly A: Stachybotrys chartarum (also known as priate combination of high humidity and depending on the amount or type of mold, Stachybotrys atra) is a greenish-black temperature. sampling and culturing would not be mold. It can grow on material with a high reliable in determining the health risk. CDC cellulose and low nitrogen content, such Q: Do structural adhesives cause mold to recommends that if the occupants are as fiberboard, gypsum board, paper, dust, grow more readily? susceptible to mold and mold is seen or and lint. However, it is not necessary to A: A recent study on fungal susceptibility of smelled indoors, there is a potential health determine what type of mold may be pres- pine and aspen oriented strand board risk and the homeowner should arrange ent—all molds should be treated the same (OSB) found that the amount of mold for mold removal(3). with respect to potential health risks and growth on both OSB types was approxi- removal(3), including (per the CDC) Stachy- mately equal to the mold growth on solid Q: If a qualified environmental lab took botrys chartarum. Mold growing in homes aspen(11). These results indicate that the samples of the mold inside a home and and buildings, whether it is Stachybotrys adhesive in OSB has little or no effect returned the results, can CDC or anyone chartarum or other molds, indicates that on mold growth. Additionally, molds grow else interpret these results? there is a problem with water or moisture best on sources with freely available A: Standards for judging acceptable, that needs to be addressed. nutrients(12), and since the cured resins tolerable, or normal quantities of mold used in structural adhesives are a poor have not been established. If the home- Q: How common is mold, including source of freely available nutrients, these owner decides to pay for environmental Stachybotrys chartarum, in buildings? adhesives are generally not associated sampling for molds, CDC recommends that A: Molds are very common in buildings and with mold growth. the following items be addressed before homes and will grow anywhere there is the work starts: moisture. The most common indoor molds Q: If someone thinks they have mold in their • Who will establish the criteria for are Cladosporium, Penicillium, house, should they test for it? interpreting the test results? Aspergillus, and Alternaria. The scientific A: According to the EPA, sampling is • What are their qualifications? community does not have accurate infor- unnecessary in most cases where visible • What will be done, or what mation about how often Stachybotrys char- mold growth is present. Since no EPA or recommendations will be made based tarum is found in buildings and homes. It other federal limits have been set for mold on the sampling results? is less common than other mold species; or mold spores, sampling cannot be used Keep in mind that the results of samples however, it is not considered rare(3). Frequently Asked Questions About Mold 2 Technical Resource Sheet 1504 | August 2018 Frequently Asked Questions About Mold Q: Will mold affect the structural integrity of is present. Indoor mold growth can and it breaks just above the blade like a carrot the wood in my home? should be prevented or controlled by snapping in half, it is decayed(15).