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Preventing Mold

By Stephen Varone, AIA and Peter Varsalona, P.E.

About a year ago, my wife and I moved into our two-bedroom apartment in a newly built condominium (not yet two years old) in Manhattan. Recently a grayish mold has started growing on our living room wall, and it has now spread down along the baseboard. We’ve been diligently wiping down the areas every time the mold starts to appear, but it eventually grows back. We’re concerned that the mold may soon show up in other parts of the apartment— in fact, our neighbor on the other side of the wall also has been having problems with mildew. Aside from the stains the mold leaves, we’re worried that it could aggravate my wife’s allergies and pose a risk to our health in general. How do we determine the cause of the mold, and what do we do to stop it? Should we have testing done? Will we need to replace the sections of wall that have been affected to prevent any dormant mold from growing back?

The presence of mold in buildings has become arguably one of the biggest concerns in the co-op and condominium community over the past few years. In several high-profile cases, residents have sued boards and developers claiming that mold caused or worsened their health conditions and destroyed their apartments. Tabloid headlines screaming “Killer Mold” and “Fungi Fear” have amplified the scare. Mold has become such a hot-button issue that the mere mention of the word is cause enough for anxiety among building owners, managers, and residents.

Often lost in the sensationalism, however, is that mold can be found almost everywhere, and not all of it is toxic. In fact, most mold species are not hazardous to human health, and for the ones that are, the connection between the mold and conditions such as allergies and respiratory problems is not well understood.

That being said, mold in an apartment is never a good thing. Even if it is one of the many non-toxic species, the presence of mold means water has found its way into the building or is escaping from within. If the water hasn’t already caused damage, it eventually will if it’s not stopped.

Mold thrives best in moist environments between 32 degrees and 100 degrees Fahrenheit, where it feeds on organic material (i.e., containing carbon), such as gypsum board (Sheetrock), plaster, wood, particleboard, wallpaper, paint, and carpets. Inorganic substances such as metal and concrete are not mold friendly, but mold can grow on the paint applied to steel beams and concrete walls.

Consistently wet surfaces, such as those caused by leaking baseboard heaters, provide a welcome mat for mold growth.

In your case, because the mold is clearly visible on the living room wall, testing probably won’t tell you more than you already know—that is, if you can see mold, it’s there. Mold, however, may be present even if it can’t be seen. A musty or mildewy odor is one indication that mold may be growing behind a wall, underneath a carpet, within a crawl space or vent, behind wall paper or baseboard trim, or in any number of out-of-the-way spots. In such cases, a mold or environmental specialist should be called in for testing. Air sampling can sometimes detect airborne mold spores, but false negatives are not uncommon with such tests, so probes of the suspected areas will provide a more comprehensive evaluation.

Tracking the Moisture
After determining the extent of the mold formation, the next step is to locate the source of moisture causing it. The usual suspects of external leaks include deteriorated parapet walls and the coping stones on top; missing or defective flashing and counter-flashing; torn or deteriorated roofing membranes; defective lintels, windowsills, caulking, and pointing; and poorly waterproofed air conditioner sleeves. Foundation walls are also susceptible to seepage when the surrounding ground slopes into rather than away from the wall, causing rainwater to accumulate between the grade and wall. No matter where the water originates, it doesn’t take long to create a serious problem: One drop of water every six seconds can amount to more than 100 gallons a day—more than enough to provide a hospitable home for mold to grow.

Mold can also develop from moisture originating from inside the building, especially in modern construction such as yours. Many “airtight” newer buildings rely on energy efficient central heating and cooling systems, with extensive piping and ventilation ducts running behind walls, above ceilings, and under floors. If proper insulation is not in place, condensation forms along these conduits as they carry air or water much colder than the air surrounding it. Trapped behind closed spaces, the moisture from sweating pipes and ducts can saturate the interiors of walls, floors, and ceilings.

Other sources of interior moisture are improperly pitched drip pans in air conditioners and fan coil units, leaky pipes, and galvanized steel condensate drains that corrode and clog over time. Bathrooms and kitchens, which typically generate more moisture than other rooms, also generate excess humidity if not properly ventilated.

Whenever mold is present, it’s recommended a licensed engineer or architect conduct a thorough leak investigation to determine the source(s) of the water penetration. Tracking the cause of the moisture isn’t always straightforward because water can travel far and wide from its origin. Moisture meters, investigative probes, and infrared thermal photography are some of the tools used to detect leaks and determine the extent of the water infiltration beyond what is visible. The key is to find all the sources of the moisture, not just the obvious ones. If the inside and outside of the building are not watertight, it’s likely the mold will return. In addition to mold and the unsightly stains and discoloration it leaves behind, more serious damage could result from unattended leaks and water buildup.

Depending on the extent of mold in your apartment, it may be necessary to replace the water-damaged areas. Merely wiping the affected surfaces clean, even with a strong agent such as bleach, will not kill all the mold, only the surface layer. Chances are if the source of moisture is behind the wall, the hidden side has suffered more water damage than you can see, and it likely contains mold as well.

A word of caution: mold-damaged materials should not be casually ripped out. Hire a mold remediation expert, who will take proper precautions such as wrapping the area with plastic sheeting (to keep mold spores from further spreading through the air) and carefully removing all the afflicted areas, not just those where the mold is visible.

Breaking the Mold
The key to preventing mold formation is controlling moisture and avoiding interior designs and materials that provide a fertile ground for mold growth. Here are some steps you can take:

• Fiberglass insulation around pipes tends to sag over time, allowing air to come in contact with the pipes and form condensation. A brushed-on vapor sealant on top of the insulation helps the insulation adhere better, keeping a tighter wrap.
• Air intakes, diffusers, and filter boxes should be cleaned annually, and ductwork every five to 10 years.
• Gypsum board tends to absorb water, so Greenboard, a water-resistant version, is a better choice when replacing moldy wall sections or installing new ones. Wonderboard, an even more water resistant fiberglass-mesh cementitious backerboard, works well behind ceramic tile (which is very mold resistant because it’s inorganic) for bathrooms and kitchens, where moisture is prevalent.
• Particleboard furniture does not resist mold well, so keep it away from windows and moisture-prone areas.
• Minimize the use of vinyl wallpaper and trim, which can trap water.
• Storm windows create an insulating space that helps reduce condensation.
• Regular wet cleaning of carpets is recommended. For bathrooms, small area rugs that can be taken up and washed are preferable to large, hard-to-remove carpeting.
• Use a fungicidal paint for surfaces in high humidity areas.

Proper Ventilation
If you take long, hot showers, cook frequently, or keep lots of plants in your apartment, be sure there is adequate fresh air and ventilation to avoid high humidity. The New York City building code requires that exhaust fans in kitchens have an airflow of at least 150 cubic feet per minute (cfm) for proper ventilation, and 50 cfm in bathrooms without a window. Because mildew starts to develop at relative humidity levels greater than 60 percent, HVAC systems are typically designed to maintain a level at or below 50 percent. The city code also stipulates that the area of window openings be at least 10 percent of floor area in that room, and half of those windows must be operable.

Have a Plan of Action
Unlike asbestos, which has specific city, state, and federal regulations for remediation, mold tends to trigger reactive, haphazard measures. While finding and stopping the source of the water/moisture buildup are necessary steps, all too often little is done to prevent mold in the first place, and problems are usually addressed only after mold spores have reared their ugly little heads. By that time, the damage has already been done.

Given the potential health, legal, and financial issues at stake, it’s important for property managers and boards to have an action plan in place to deal with water penetration and the potential for mold formation. A regular building maintenance program, especially at the roof level, is great insurance against water problems. When leaks or excessive moisture are detected, the source(s) must be quickly pinpointed and fixed. Wet surfaces and materials must be dried out as quickly as possible, preferably within 24 to 48 hours. Musty odors and stained areas should be tested by a mold expert, and mold-damaged material needs to be remediated by a professional. Keep residents informed about what’s going on to allay any fears, and encourage them to report any problems of leaks, moisture, cracks, or discoloration not just in their apartments but in common areas as well. A joint effort between management, board, residents, and building staff is the best way to keep mold away.

Stephen Varone, AIA is president and Peter Varsalona, P.E. principal of RAND Engineering & Architecture, PC. This column was originally published in the June 2004 issue of Habitat Magazine.

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