Buildings

Mold

by Arnie Katz

Q:  All of sudden, we have a bunch of black mold growing on the wall in the bathroom. My neighbor said it might be "killer" mold, and we better do something quick. I called a local company that specializes in this, and they gave me an estimate of $20,000 to fix my house. Is this stuff really that dangerous, or is this just another scam to separate people from their hard-earned money? —Bill T, Durham

A: Great question, Bill. Unfortunately, the answer's not easy. There are some molds that are very toxic to some people. These seem to be fairly rare, although I don't think there's any real data on how prevalent they are. It's much more common for folks with conditions like asthma and allergies to react to some molds, which can contribute to making them sick. So the first thing to do is ask whether anyone in your house has symptoms that might be caused by the mold exposure. If you think they might, go to a doctor—one who actually knows something about these issues—and try to determine if your symptoms are actually related to the mold in your house.

In the meantime, there are two things to do—regardless of whether the mold is definitely making someone sick or not. The first thing to do is to figure out the source of excess moisture in the house. The presence of mold always indicates the presence of excessive moisture. Regardless of the species of mold, the solution will always include stopping the moisture. Most of the time, spending hundreds of dollars on lab analysis to identify the long Latin name of the particular mold visiting your home is about as useful as naming the mice chewing on your pantry.

Sometimes the source of the water is easy to find: a plumbing leak, a family member taking long showers without using the exhaust fan, an exhaust fan that doesn't work well, an unvented heater or fireplace. Sometimes it's not so obvious: a combination of factors that created ideal conditions for some mold to vacation in your bathroom. You may need to hire someone who knows what to look for. In some communities, the home energy raters have had extensive training in building science, including moisture diagnostics. Sometimes, HVAC contractors understand these issues, as do some general contractors, some home inspectors, and even some mold remediation specialists.

The second thing to do is to clean up the mold. If it's fairly recent, it may just be on the surface, and you can wash it off with water, a little detergent, and some elbow grease. Most public health agencies no longer recommend using bleach, as exposure to the chlorine may be worse than exposure to the mold for some folks. If it's fairly extensive, and has "rooted" into the dry wall, you may have to replace some dry wall. I would consider replacing it with a fiberglas covered dry wall rather than the traditional paper covered dry wall. It's more expensive, but is much less likely to support mold growth in the future.

The key, though, is always to figure out how to control moisture in your home. Making sure bathroom and kitchen exhaust fans are actually working, actually ducted to the outside, and are actually being used will often help a lot. Managing the water around the foundation of your home—proper gutters, downspouts and drains and sloping the ground away from the house—will help. Cover the ground in the crawl space with thick plastic, and consider installing a closed crawlspace system. Before your air conditioner dies, have someone do a proper load calculation to determine the right size unit for your house. Over-size air conditioners that don't run enough to remove the moisture are very common, and knowing what you'll need before the unit dies on a 97 degree day in August will enable you to get it right.

Don't let yourself be panicked into spending a lot of money without doing your homework. Here in North Carolina we live in mold heaven. We certainly don't want it in the house, but let's use some common sense.