Q&A: mold maintenance.

I seem to get cold symptoms, lung problems, and joint pain in the summer, especially when it's rainy. I think my house is moldy. What can I do for my house as a quick fix to get rid of the mold and start feeling better while I look into long-term solutions for the problem?

When humid air (58% and higher) moves indoors, it naturally gravitates to the closest porous surface, like drywall, wood, fabric or carpet, creating mold. It is essential to keep your house dry (dehumidified) and air conditioned (or heated) when the humidity is above 58% outside. In our region, 58% or higher outdoor humidity occurs over 200 days out of 365 in a given year.

This means that the only way to control indoor mold levels in our area is to dry your house out. A quick fix may work, but you will have to "maintain" the fix. The first thing you must do is stop the moisture from coming in. If you live on a crawl space or an unconditioned or unfinished basement, this is where you need to start. Stop any water leaks or moisture infiltration through the block or dirt. Then make sure all your water drains away from your home. You can do this by creating a gravel drain bed around the perimeter of your home. Eliminate any visible surface mold (as much as possible) on the inside walls. This will do nothing for mold that is in the structure itself, that is why this is a "band aid" at best.

If you are dealing with a dirt floor, then I suggest laying a quarter inch layer of granulated lime on the dirt followed by black 6 mil plastic sheeting. This will help to smother any mold in the ground, and lime is a natural deterrent to mold. Next, install a basement-size dehumidifier along with humidity gauges. Constantly monitor the humidity and have the dehumidifier drain to the outside. Your humidity should stay at 50 to 55 percent.

Once you have followed these steps in your basement or crawl space, then you should move to the main level of your home and dry it out as well. Do not rely on natural ventilation (opened windows) when the humidity outside is above 58%. If you do, you will have mold in your home. Rely instead on air conditioning and dehumidification. Monitor the humidity inside and out and take responsibility for drying your house, in turn, taking responsibility for your health. They should work together like a system. Once the humidity levels are at a consistent level of 42 to 58 percent indoors, then ozonate room by room. I suggest doing this at each change of season.

The next step to eradicating mold spores in your home after you have gone through the steps of finding and taking care of the sources is to use an ozonator. This is a controversial step. I can tell you from personal and professional experience that if this tool is used correctly, it does work. Please refer to the internet for more information on ozone and ozonators.

Having your HVAC ducts cleaned each season is important, especially if you rely on natural ventilation. Mold spores are likely proliferating there. Make sure the duct cleaning company simply vacuums them out. Do not allow them to use the fungicide they like to put in the ducts once they are clean. I have found it to be toxic on sensitive immune systems. If you cannot afford to have your ducts cleaned, then placing the ozonator in front of your HVAC cold air returns will distribute the ozone into the ducts, helping to lower the mold levels. Again, this is a "band-aid." It will have to be repeated many times over the year to maintain lower levels of mold.

Cindy Meehan-Patton is president of Shelter Ecology, Inc. founded in 1992 and offering green and healthy home products, healthy home consultations, and architectural and interior design services. For more information go to www.shelterecology.com

Our house was built on a slab foundation, and we're having lots of problems with mold. What can we do?

Mold is the result of high relative humidity (RH) levels. Mold thrives in RH levels of 60 percent and higher. To control mold, you must control moisture. This is easier said than done in this part of the country.

Your first question should be: "From where is the moisture originating?" Typically, moisture can enter the house in three ways--bulk water, vapor diffusion, and on the path of airflow.

If there is a flow of water entering your house from the outside, you've got bulk moisture issues. This will probably require your attention on the outside of the house, focusing on the site grading and foundation drainage.

Vapor diffusion is a bit more mysterious. Since slabs are made of concrete, which is a porous material that likes to wick water via capillary action (refer to the celery and food coloring experiment in elementary school). This capillary action is typically battled in new construction by the use of a vapor barrier beneath the concrete slab, with 4-6 inches of gravel beneath the gravel. Capillary action can only take place within small pockets of air. The air pockets between the chunks of rock provide what is called a "capillary break." If you live in an older home, your slab may have been poured directly on the dirt. If this is the case, you probably don't have a vapor barrier beneath the slab either.

Moisture could be entering your home is by "piggy-backing" on the flow of air. Warm air holds more moisture than cool air. Think of warm air as a balloon that is full of water. When the balloon shrinks (air cools down), it is no longer able to hold the same amount of water. It spills out, or condenses. The temperature at which air will condense is called the "dew-point." The higher the RH level is, the higher the dew-point. So on days where it is extremely humid outside, and you choose to open your doors, the air that comes in will condense on any surface that is below the dew-point.

Slabs are inherently cooler than most other surfaces in a house, and therefore prone to condensation issues in the summertime. You should think twice about placing carpeting on a slab floor, if indoor air quality is important to you. When sized correctly (bigger isn't better), an air conditioner also acts as a dehumidifier. If you don't have an air-conditioner, then an efficient dehumidifier is another option.

Moisture is tricky. Even if the RH of the ambient air within your home is low, you can have high levels of RH at the surface of cold objects (like your glass of iced tea ... or your slab floor). This is referred to as a "micro-climate" within the home.

For more information about sizing your air conditioner, see our Healthy Home Q&A in our August 2005 issue.

Isaac Savage is president of Home Energy Partners, a Building Performance Contracting firm that is located in Asheville, NC. He can be reached at 828-350-1155 or on the web at www.HomeEnergyPartners.com

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