Mold Prevention and Construction Materials

Many construction materials are available in a “mold-resistant” or “mold-proof” variety. Drywall is available without the traditional paper covering, which has been the site of much hidden mold growth. Mold-resistant plaster and paint incorporate a fungicide to keep mold from growing on surfaces. Mold-resistant lumber is impregnated with substances that makes it more waterproof as well as with fungicides. Interior finishing products, such as bathroom tiles, are sometimes advertised as mold-resistant.

However, keep in mind that mold-resistant building materials are more expensive and none of them can promise that no mold will grow under any conditions. Mold-resistant building materials might give homeowners an extra edge in areas of heavy rainfall, such as the Pacific Northwest, or high humidity, such as the Gulf Coast. But they must be used properly, according to manufacturer directions, and they cannot overcome basic design flaws that trap moisture. Talk to your building contractor about the possibility of using mold-resistant materials.

Mold Prevention and Construction Techniques

The greatest deterrent to mold growth is proper construction methods that keep ventilation and circulation a top priority, to control indoor moisture. Builders can take these precautions to guard against future mold problems:

• Seal all air conditioning duct joints where condensation might occur.
• Use wallpaper with an air-permeable backing, to keep from trapping moisture against walls.
• Provide for proper drainage of rainwater from the property, by correcting the grade and by using gutters and downspouts.
• Provide a floor drain near washing machines.
• Use water-resistant drywall backed by cement backer board for extra stability.
• Paint bathrooms with paint containing fungicide (or mildewcide).
• Install a high-powered bathroom ventilation fan.
• Avoid dirt floors in crawlspaces; cover with plastic sheeting. Open crawl spaces so they have the same ventilation as the rest of the living space.
• Install a layer of gravel under cement basement flooring to keep moisture from soaking up through the floor.
• Thoroughly waterproof the exterior of the foundation on all sides.
• Carefully seal the areas around all windows.
• Carefully seal any breaks in the roof around chimneys or vents.
• In cold climates, consider adding heating elements to gutters to prevent ice dams from forming on the roof.
• Avoid using fake stucco or other finishes that tend to trap moisture.
• Avoid using cellulose insulation; choose wall insulation designed for mold resistance.

Minimizing Mold Problems with Ventilation

The single most important thing you can do to keep mold from developing in new construction is to plan adequate ventilation. Ideally, each room should have multiple ways for air to enter and leave, including windows, doors, and vents. Whole-house air conditioning systems with proper drainage can pull a great deal of moisture from the air while moving air through the living space. Ceiling vents and roof fans can help draw air up through the house and out the top, providing a steady air flow that will tend to dry any moisture that might otherwise accumulate. Exhaust fans can keep kitchens and bathrooms dry.

If you are building a home, talk to your architect and contractor about designing in extra ventilation, to prevent mold build-up and to help your family breathe easier.

Toxic Mold After Flooding

Flooding, whether it’s caused by a gradually rising river or by a hurricane storm surge, poses the greatest danger of toxic mold development. Wet surfaces invite mold growth, and thoroughly saturated wood building framing can take a long time to dry out, especially if the rain continues to fall or the water continues to rise.

The first priority after a flood should be to dry out the living spaces as quickly and completely as possible, preferably within the first 24 to 48 hours after the water recedes.

• Set up fans, open windows and doors, and increase circulation as much as possible.
• Soft, upholstered furniture and carpeting might have to be taken out of the house so it can dry in the sun, or it might have to be discarded.
• Early mold growth should be cleaned with a strong bleach solution or fungicide cleaner, but after mold has begun to multiply, professional remediation probably will be required.

Mold Exposure and Rescue Workers

If you are trying to rescue your home or the home of a fellow disaster victim, be aware of your mold exposure. Wear a particulate respirator (a form-fitting mask that covers the nose and mouth, designed to purify the air you inhale by filtering out airborne particles) and goggles as well as gloves and clothing that can be double-bagged and discarded after use.

After working in a mold-infested area, shower and wash your hair thoroughly as soon as possible, to keep from spreading mold spores or irritating your skin. Many rescue workers who helped victims of Hurricane Katrina subsequently had health problems because of mold exposure.

Toxic Mold and Hurricane Katrina

The flooding caused by Hurricane Katrina left New Orleans and other warm, wet Gulf Coast communities with the perfect environment for mold growth. The problem was compounded by the fact that many homes affected by Katrina were left without electricity to power ventilation fans.

Both New Orleans and Mississippi reported significant increases in cases of respiratory problems in the months following Katrina. Government officials urged families whose homes showed more than 10 square feet of visible mold to seek professional mold remediation and to not reoccupy the homes until the remediation was complete.

Much of the repair work done on Hurricane Katrina-ravaged homes was done with mold-resistant paint and drywall, to keep mold at bay in the new construction should another hurricane arrive. Anyone owning property within a flood plain might consider anti-mold construction methods as an investment against future disasters.

There are two basic categories of mold testing: taking samples from the air and testing samples from a surface.

Mold Air Samples

Mold air samples test how many mold spores are present in the air; spores are the means by which mold reproduces. It’s possible that some mold colonies might be present, but have not yet matured enough to begin reproducing. That is why surface testing is also important.

Mold can cause health problems when it is ingested, and can cause skin reactions when it is touched. The most serious mold health problems are caused by inhaling mold. This might be because mold exposure by inhaling mold spores is likely to occur over a long range of time, whereas a person might only consume or have skin contact with mold occasionally.

Mold air samples are the best way to determine how much mold spore is present in the air you breathe. The two main types of tests are:

• A bioaerosol test involves drawing a stream of air into an aluminum device for five minutes. The device contains a petri dish full of growth media, and it is held closed by clamps and O-rings to prevent contamination by air other than that being tested. The petri dish is examined by a laboratory over the course of a few days to see if mold has begun to grow. If mold does grow, it can be further tested to determine the exact species. The bioaerosol test is expensive and must be conducted with exacting scientific procedures, to ensure the results are accurate.
• A spore trap is a device that allows airborne particles to settle on an adhesive media. It will trap mold spores in the air, but does not allow them to grow, so they can’t be tested to determine the species. A spore trap will trap anything airborne, including insects, skin cells, and pollen — the components of household dust. Laboratory analysis is needed, but this test is faster and less expensive than air sampling.

Mold Surface Testing

Mold surface testing involves taking small samples from areas of mold.

• Surface samples can be scraped off visible mold and sent to a lab for analysis. The process is relatively inexpensive and can determine the exact species of mold involved, but doesn’t always indicate how much mold spore is present in the air. Collecting surface samples also poses a risk to the collector and those nearby, as it “stirs up” mold.
• Sterile swabbing involves dabbing an area of mold growth with a sterile cotton swab saturated in growth media, which is then immersed in more growth media and sent to a lab for analysis. This method of mold testing is inexpensive and less dangerous than scraping off a sample, but it doesn’t work on dry surfaces or detect mold hidden within porous surfaces.

No mold test is 100 percent accurate in determining the scope of a mold infestation problem. It is possible for hidden mold to be causing severe medical problems, even if mold tests show a minor infestation. The intensity of mold exposure is more closely linked to serious medical problems; for example, a person sleeping next to a wall hiding a serious growth of toxic mold behind the paneling might suffer from serious medical symptoms, but a mold spore trap would show only a few airborne spores throughout the house. The person most affected in that situation would be breathing the mold spores almost directly from their source.

Five Steps for Removing Mold

1. Resolve your moisture problem. If water is leaking, dripping, or accumulating anywhere on your property, you will have to figure out where it’s coming from and stop it. If you have high humidity in a room from other sources — aquariums or house plants, for example — you will need to use a dehumidifier or increase ventilation to the room to bring the humidity down. If your living space has become wet because of a flood, broken water main, or other cause, your first step should be to thoroughly dry the space, using ventilation, fans, heaters, dehumidifiers, or disposable absorbent materials (such as paper towels). Work quickly. It takes only 24 to 48 hours for mold to get a foothold in damp material under the right conditions.
2. Protect yourself. Have children, the elderly, anyone with a compromised immune system from chemotherapy or HIV disease, or anyone with a known allergy to dust or mold, leave the building for the duration of your cleaning project. Leave an air purifier running near you as you work. Rent and use a high efficiency respirator designed for particle removal, especially for large jobs. Wear goggles that form a tight seal around your eyes, and rubber gloves. Wear clothing that covers all exposed skin; plan to remove and discard the clothing outdoors, if possible, or remove clothing and seal it into plastic bags before leaving the containment area. Put on fresh clothes that are handed to you through the window or that you bring in with you sealed in several layers of plastic. Do not touch any surface before you leave the room.
3. Contain the mold. Mold will release spores when it is disturbed, so begin by sealing off the space you need to clean. Mold spores can travel attached to dust or floating on air currents. Each mold-contaminated area must be sealed off, one room at a time, using plastic sheeting and duct tape over doors, windows, cracks, and air vents. If the room has an outside window or door, leave it unsealed and place a fan blowing OUT to draw air and mold spores out of the living space while you work. Turn off any central air or heating systems before you begin.
   
4. Clean and disinfect. Because mold loves damp conditions, most patches of mold growth will be moist. Any mold that has dried is especially dangerous, because the powdery mold spores will easily become airborne. If you encounter dried mold, mist it with water before cleaning.
   • Non-porous surfaces, such as metal, glass, hardwood, plastics, and concrete: scrape off as much mold as possible, then scrub with a moldicide or fungicide cleaner.
   • Porous surfaces, such as carpeting, ceiling tiles, wallboards, and porous possessions, such as upholstered furniture, clothing, and books: if an item can be thoroughly cleaned and dried, and the mold has not destroyed the surface (remember, mold is eating anything it grows on), porous items might be reusable. In most cases, however, mold-infested porous surfaces will have to be torn out and thrown away.
5. Remove mold-contaminated objects and cleaning materials. Seal mold cleaning supplies and all waste materials in heavy-duty plastic bags. Pour water used in cleaning up mold directly down the drain. If possible, do not carry mold-contaminated objects through other rooms; the sealed plastic garbage bags should leave through the window and not be carried through the house.

Allow any area you have cleaned to dry thoroughly before you remove the plastic sheeting and duct tape.

Mold removal is difficult work. If your job will take several hours, plan to work only 30 minutes at a time, taking breaks outside with the respirator off.

Consider Professional Mold Eradication

If you are unable or unwilling to take the required precautions to clean a moldy room, consider leaving this work to the professionals.

If you clean up a moldy area yourself, using all precautions, and you still suffer a negative reaction to mold — or if your mold problem recurs in the same area — think seriously about consulting a mold remediation specialist.