The New Buzz Word: Mold

Paul Eldrenkamp

When I was first entering the building industry almost 25 years ago, radon was the hot topic causing homeowner anxiety. Today it seems to be mold. I suspect that, just as radon mitigation, where needed, is pretty routine and non-controversial these days, mold mitigation will also soon be considered routine and unthreatening.

Mold risks are directly proportional to the amount of mold in a house. All houses will have some mold spores in the air; almost all will have actual mold growth somewhere inside. How worried should you really be about mold in your home? It depends on how much mold is in your house, and how vulnerable you are.

What constitutes a mold problem?

Here's two ways of thinking about the question:

1) If someone in the house is having an adverse respiratory reaction to being in the house, there's some chance it's mold-related. If a thorough visual inspection does not uncover any noticeable mold growth, one diagnostic measure would be to have a test done to compare mold spore count of indoor air versus outdoor air.

Mold researcher, Harriet Burge, has come up with a useful rule of thumb: if the spore count of the indoor air is at least twice that of the outdoor air in the general vicinity of the house, you will probably want to look more closely for mold sources in the house.

2) If you do find mold, that may not mean you have a "mold problem" in and of itself, but it is a 100% reliable indicator that you have a water problem. To grow, mold requires the right food , the right temperature range and water. The only one of these three that doesn't really belong in most areas of the house is water.

The most frequent source of water where it doesn't belong is faulty exterior details, such as roof leaks, window leaks, or poor exterior drainage that directs too much water to the basement. These are pretty obvious things that show up quickly and can be dealt with quickly.

After leaks, condensation is usually the second biggest source of water that leads to mold growth in homes. Condensation occurs when warm, moist air comes into contact with a cool surface and the water it contains loses energy and undergoes a phase change from vapor to liquid. (Water vapor does not cause a problem in homesÑliquid water does.) Condensation problems can be remedied by one or both of two means: reducing indoor humidity, or eliminating indoor surfaces that are cold enough to cause condensation.

The third biggest source of water that can cause mold growth is capillary action, typically up through basement floor slabs or through basement walls. Concrete is a very porous material and, absent some sort of capillary break such as polyethylene sheets or bituminous coatings, ground water can easily migrate through the concrete. Capillarity does not cause standing water, but it can lead to high enough moisture levels under a basement floor carpet, for instance, or behind a finished basement wall, that the environment there is very conducive to mold growth.

The best ways to get rid of mold:

1) Wipe small amounts of mold off the affected surfaces by using water and a mild detergent. (Bleach works, too, but the bleach often poses more of a health hazard than the mold.) Sherwin-Williams has come out with a bleach alternative called, attractively enough, "KrudKutter," that one of our painters, Catchlight, has started using in the interests of worker and client safety.

2) Deal with larger areas (and certainly rotted wood or plywood) by removing the affected material completely, disrupting the mold as little as possible (wear a respirator), and carefully placing the material in secure plastic garbage bags. Often, wetting the materials lightly with water (if it's not already wet anyway) will help keep the mold from going air-borne while you're bagging it.

3) Faced with big expanses of mold (very general rule of thumb would be anything more than 10 to 15 square feet or so), you might seriously want to consider a mold remediation company.

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