Question: I am an assistant school facilities manager in a small school district in Ohio. In the past five years we have been upgrading our elementary school buildings by installing air-conditioning. Unfortunately, we have had all kinds of problems with mold growing on carpeting, books and other materials. How can we both re-mediate the mold problems we have and keep them from recurring and in future upgrades prevent them from happening in the first place? -John, Ohio
Answer: The problems you describe are common throughout the Midwest,upper Midwest, and on the east coast. They tend to 'go with the territory' in such school building upgrades. There are a variety of factors that give rise to the problems you describe. They include the learning curve associated with the operation of a new system, the operation of the air-conditioning system during summer months during the day when school personnel and summer students are present and high dew point temperatures.
When new air-conditioning systems are installed, they are often operated on 'the cool side' with building temperatures in the low to mid 70s. Since in theory you don't need air-conditioning once 'no one' is in the building, the air-conditioning system is typically shut down at 4-5 in the afternoon. On most summer days that is not a problem. Problems result on high humidity days when dew point temperatures of 72-78oF occur. When humid outside air passively enters the building, it comes in contact with surfaces that are cool enough to cause near saturation relative humidities and even condensation. 'Puddling' or sweating on floor tiles, desks, etc. commonly occurs. In tiled corridors the floors become slippery enough that one can literally 'skate' on them. If your buildings are carpeted, you may even see a 'hairy' growth on carpet. This is particularly noticeable in the entry/exit area for the cafeteria. Such problems can be both re-mediated and avoided. Because the carpeting is synthetic, mold cannot grow on it. Mold grows on the dust and soil particles that have collected on it.
Near the cafeteria this includes food particles. The carpeting does not need to be removed and replaced as many environmental consultants recommend. Rather it should be rigorously cleaned (using steam extraction) and treating it with a nonvolatile, low mammalian toxicity biocide. It should be followed by more intensive vacuuming( more than once a week. I have evaluated such a remediation using total mold sampling. Such sampling indicates that remediation is very effective.
Books can be re-mediated by the procedures described in a previous posting (see archive Salvaging moldy books). It is undesirable to run the air-conditioning system any colder than 76oF. In southern states many building systems are operated no cooler than 78oF, because of the high energy costs associated with latent heat removal. Turning the AC system off because 'it is not needed' when no one is in the building is asking for trouble. Outside air will come in passively (actually because of temperature differences, it will be sucked in) and come in contact with coal surfaces. As such, summertime AC operation should be around the clock. It can be run on the 'warmer side' during evening and nighttime hours. November 1, 2001
Dr. Thaddeus Godish is a Professor Of Natural Resources And Environmental Management at Ball State University. His email address is 00tjgodish@bsu.edu