May 1 2007 10:34AM | Permalink | Email this | Comments (3) |
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The basic principles for preventing mold in houses are relatively simple. When one considers how straightforward they are to list, it’s easy to think that preventing mold involves little or no difficulty at all.  On the other hand, for those who have ever been frustrated by a recurring problem with mold that refuses to yield even to elaborate measures, it is easy to see why some people believe that water and mold are unavoidable. Of course, realistic approaches to preventing mold fall between these two extremes.  The concepts and principles are simple—but designing, constructing and maintaining a building are not.Like other elements of modern society, buildings are complex, multifaceted creations pieced together from thousands of relatively simple parts. These are assembled into a myriad of interacting and intermingled components.  A successful strategy for preventing mold requires taking a few simple but powerful basic concepts, and making sure they are consistently and correctly applied to the hundreds of individual details that are involved in creating a building.

So, let’s talk about basics. A logical place to start is the most fundamental question of all: what are the basic conditions needed for mold to grow? It is well known that molds require the following to thrive: (a) mold spores, (b) a source of food, (c) water and (d) temperatures conducive to growth of the particular species of molds.

Mold spores are the microscopic reproductive units, or “seeds,” produced by molds.  They drift in the air to settle on surfaces and develop into new individuals. Mold spores are ubiquitous in our environment; they are literally everywhere. You cannot see them, but unless you happen to be in a high-tech clean room protected by HEPA or ULPA filtering equipment and special containment zones, you inhale and exhale mold spores with every breath anywhere on earth. No building or building material is free of the presence of mold spores. The potential for mold growth is always present.

Like all living things, molds must have food to grow.  Molds are fungi and their nutritional needs are fairly simple. They require a source of carbon, the primary building block of cells, and traces of other elements essential to the chemistry of life.  Hence, molds feed on organic materials that they convert into their own substance. Wood, paper and starch are common to many building materials and provide a ready source of nutrients for molds. Even inorganic materials can accumulate dust, dirt or films from various sources that have sufficient organic matter to support mold growth.  Just look around as you walk through the city, and you will find that it is not unusual to see mold growing on concrete, metal or glass surfaces where dirt can accumulate and they are not kept dry.

“Dry.” That one word is the key to a successful strategy for controlling mold.  I mentioned temperature earlier, but among the more than 100,000 different species of molds, hundreds have evolved to fill the same ecological niche as humans.  If the building is habitable, it will suit these molds quite well. So temperature is not a practical alternative to be used as a controlling factor in the building.Moisture, on the other hand, can and must be managed. There are many excellent products, such as Sheetrock^® brand MOLD TOUGH™ gypsum panels, that are mold resistant and can be part of a successful mold-prevention strategy.  But mold-resistant panels or coatings do not provide a complete defense against moisture intrusion and should not be used as a substitute for proper moisture management.  As reported by the U.S. Institute of Medicine in its report “Damp Indoor Spaces and Health” (National Academies Press, 2004) there are many good reasons besides mold why damp indoor spaces should not be tolerated.

In future installments, we will talk about sources of building moisture and how to keep buildings dry. For the most part, these are relatively uncomplicated common-sense concepts.  But, as the adage goes, “The devil is in the details” and there are many, many details to consider.  As with any complex undertaking, however, the solution lies in breaking things down into manageable pieces and that is what we will begin to do.