Few topics elicit as much fear as mold in houses. That’s good news for those inclined toward litigation, whose theme is “Mold Is Gold.” And it’s good for newspaper writers, too, as the word “MOLD!” in a headline will get attention.
The bad news is that most of us remain ignorant about how and why mold grows in our homes, and how our actions contribute to that. This is also about sustainability, as the goal of green building is to create homes that last and that do not have to be torn down and hauled to the landfill.
Mold spores are everywhere. Whether or not they have the means to flourish and reproduce is the question. The topic is so volatile that if you ask some builders if your house has mold, they may reply: “I’m no expert on mold. You should consult an expert.”
So, who’s an expert? I met one yesterday at a builder’s conference in Long Beach and sat in on his seminar titled: “Mold in Houses: Truth and Consequences.”
The presenter, George Tsongas, is an expert in the field known as “building science.” Tsongas has four engineering degrees from Stanford, including a Ph.D., and taught mechanical engineering for 29 years at Portland State University.
According to Tsongas, there’s a lot of focus on lawsuits and health risks of mold, and he doesn’t want to minimize those risks, especially for people whose immune systems are weak. But what gets short shrift is an understanding by building occupants (people like me and you) of what causes mold, and what changes in lifestyle we can make so that mold will not flourish.
The key is to keep the relative humidity in the house to less than 80 percent. Relative humidity is dependent on both the moisture in the air and the temperature. The higher the relative humidity, the more mold likes it. Tsongas said 50 percent relative humidity is even better, though difficult to achieve.
While it’s expensive and complicated to measure various types of mold spores in a home, it is very simple to measure the relative humidity in your house, and to take actions to reduce it. Radio Shack sells a good hygrometer, which measures relative humidity, for about $20.
To reduce the amount of moisture in indoor air, here are some strategies:
— Install good, quiet exhaust fans in bathrooms and use them. Tsongas suggests it takes at least one hour after a shower is over for the fan to eliminate the resulting moisture in the air. To determine if your fan is pulling properly, take the “Tsongas toilet paper test” by placing one square of toilet paper against the fan and see it the suction will hold it there. If not, the fan is not sufficient. Automatic fans that stay on until the moisture is gone are preferable, and those will soon be required by the Oregon building codes.— Vent kitchen exhaust fans to the outside. Some kitchen fans suck cooking odors into filters above the stove, but not to the outside, which does nothing to remove moisture. The burning of combustible fuel is a major source of moisture in the air. Clothes dryers should also be vented to the outside.
— Don’t allow downspouts to channel water into the foundation, where excess water will cause wood foundations to rot and concrete foundations to wick water far into the house. Inexpensive extenders will channel water away from the house. If you’re landscaping, be sure the ground slopes away from the house, not toward it. Putting thirsty tropical plants right up against the foundation is not wise. And be sure spray from lawn sprinklers does not hit the building.
— Limit the number of large fish tanks and house plants, both of which put a lot of moisture in the air, or take steps to remove that moisture from the air via a dehumidifier (mentioned below).
— For musty closets, install louvered doors to allow infiltration of heat and air from the bedroom. Colder air can handle less moisture, which means it will condense more quickly, and give mold what it needs to grow.
— If your house floods, start drying it out immediately. To remove visible mold, scrub it with soap and water, then take care of the cause.
— And finally, limit the number of people who live in a small space. Each person is responsible for putting an average of three gallons of water a day into the air, Tsongas said, when you factor in showers, cooking, laundry, breathing, perspiration. So eight people living in a 700-square-foot apartment, for instance, will result in a lot of moisture in the air, and this will create the conditions where mold can flourish. In those cases, a dehumidifier can help, and Tsongas suggest the top-of-the-line Sears model.
If you own rental properties where a lot of people may be living in a small space, you can help protect them from mold issues, and yourself from litigation, by installing a dehumidifier that drains via a hose to the outside, eliminating the need to empty it. Some landlords now include a mold addendum in the rental agreement that specifies the tenants’ responsibility for cleaning up visible excess moisture.