Mold growth in homes is the hot topic in the home building industry today. Headlines tout the danger of exposure to mold in our homes and at work. A member of the fungi family, mold comes in thousands of varieties and exists in every indoor and outdoor environment. It is a natural and necessary part of the ecosystem in which we live. Although many types of mold have positive benefits, there are several strains that can lead to health problems if allowed to flourish indoors.

Who Is At Risk? Exposure to certain types of mold can cause health problems. The sensitivity of individuals and the exposure amount varies so widely that there has been no “safe” threshold defined by authorities. According to the Center for Disease Control (CDC), most people experience no reaction to “normal” mold exposure, however some individuals exhibit great sensitivity to mold exposure, much like those affected by hay fever. Children, senior citizens, and people with weakened immune systems may be more vulnerable to mold exposure. Although “toxic mold” is the phrase most often seen in headlines, the Environmental Protection Agency (EPA) and the CDC state there is very little current scientific evidence connecting mold exposure and extreme illness, considering the low levels of exposure in most homes.

If Mold Has Been Around Forever, Why Are We Seeing So Many Problems Now? Building practices and materials have evolved at a rapid pace in the United States during the past century. Today the predominance of organic building materials, such as paper-faced drywall, wood framing, and plywood sheathing, provide a food source for mold growth. Also, increased energy costs and a limited supply of fuel have forced us to construct more energy-efficient buildings. Past construction practices allowed moisture from cooking, bathing, and other occupant activities to readily escape, along with conditioned air. According to the National Association of Home Builders (NAHB), we build homes that are 50% more energy efficient than 30 years ago. Sealing the building envelope against air loss is critical in achieving this performance. The problem arises when moisture and humidity levels are uncontrolled.

What Does Moisture Have To Do With It? Mold typically found in homes is a living organism and requires three favorable conditions in which to grow:

  • Temperature range: Between 40F and 100F
  • Food source: Organic material such as wood, dust, or paper
  • Moisture: Water or water vapor from high humidity, plumbing, or roof leaks

People need the same conditions to survive. Of the three components required for mold growth, moisture is the only one we can control while maintaining comfortable living conditions. Often, the local weather report includes mold exposure for sensitive individuals.
Where Does This Moisture Come From? Leaks and flooding: Most major mold problems are attributed to large quantities of water. Plumbing, roofing, and walls can develop leaks. This is often due to deferred maintenance, storm damage, or improper material installation. Undetected, a small leak can lead to major problems. Lawn sprinklers should be positioned to spray away from the home's exterior walls. Homes should be dried out within 24 to 48 hours of a leak or flood.

Condensation: Everyone is familiar with condensation of water vapor on a cold beverage container during a warm summer day. The same thing can happen on a window during a winter day, or on a cold water pipe or air-conditioned ductwork in a hot, humid climate. Left unchecked, this condensation can accumulate and create ideal growing conditions for mold.

Air leaks: As winds blow against a house, air can leak through gaps in sheathing, under sill plates, around doors and windows, and via electrical outlets. If there is a large difference between indoor and outdoor temperatures, water vapor can condense in wall cavities, or behind vinyl wallpaper, as it passes through insulation and cools down to the dew point. Once liquid water collects in the cavity, mold can begin to grow.

Regardless of the source, excess water should be cleaned up as soon as possible and the affected materials should be dried out. If you suspect you have serious mold growth in your home, seek advice from your insurance carrier or knowledgeable building professional.