NATIONAL REPORT—“Almost all buildings will experience some kind of water intrusion, in the form of leaks, flooding or other excessive indoor dampness at some point in their life cycle.” This statement from the Institute of Medicine’s report, Damp Indoor Spaces and Health, is an important reminder to builders, building owners and facility managers that vigilance is the best protection against liabilities for construction defects and building failures from water and moisture damage. Proactive action is far less expensive and disruptive than ignoring warning signs or being complacent about water and moisture intrusion, both of which may lead to becoming a defendant in a lawsuit.
A comprehensive review of scientific literature summarized in the World Health Organization report, WHO Guidelines for Indoor Air Quality: Dampness and Mold, emphasizes the risks associated with damp buildings, including significant damage to building materials and adverse health effects. Specifically, researchers have linked mold and damp conditions in homes and buildings to asthma, as well as to coughing, wheezing and upper respiratory tract symptoms in otherwise healthy people. In addition, dampness can cause chemicals and particles, such as lead and formaldehyde, to be released from building materials, which also can pose health risks. In addition, standing water attracts cockroaches and other pests, which can produce allergens and carry disease.
Other Noteworthy Findings:
• Indoor dampness affects an estimated 10 percent to 50 percent of indoor environments in Europe, North America, Australia, India and Japan. In certain settings, such as river valleys and coastal areas, damp conditions are substantially more severe than the national averages.
• The amount of water on or in materials is the most important trigger of the growth of microorganisms. Dust and dirt in buildings provide more than enough nutrition to support growth. Without water or moisture, these microorganisms will not grow.
• Microbial interactions and moisture-related physical and chemical emissions from building materials may also play a role in dampness-related health effects.
• Remediation of dampness can reduce adverse health outcomes. Of all the findings in the WHO report, this is perhaps the most significant for builders, building owners and facility managers. Taking this finding seriously and taking proactive steps to prevent water and moisture problems demonstrates a commitment to protecting the investment in the building, and more importantly, in protecting occupant health.
Understanding how moisture and water infiltrate a building is not only the first step in designing and constructing a building to prevent trouble, it also is the first step in diagnosing an existing problem. An indoor moisture or water problem has four components:
• Source: Any opening of any size in the building envelope may allow water or moist air to penetrate the building and accumulate on building materials. These sources include leaky windows and door openings, roof leaks, missing, inadequate or poorly designed flashing, lack of gutters, foundation and plumbing leaks, along with countless other causes. Installing these materials correctly is important for preventing leaks later on, and if leaks do occur, plugging them is critical to stopping the flow of water or moisture into the building. Another primary source is building occupant activities.
• Path: Water and moisture can travel along pipes and HVAC ducts and pool in areas far from where it entered the building. In buildings that are not properly pressurized, water vapor (damp air) may travel from the outside through the building envelope and become trapped in the wall assemblies—a common location for mold growth. In solving a water or moisture problem, investigators will follow the path back to the source. If the source of the moisture or water infiltration is not addressed, the problem will come back.
• Form: Water and moisture can infiltrate a building as a vapor, liquid water or a condensate. What form the water or moisture takes is also a good signal as to its source. Condensation within the building envelope is a common contributor to indoor mold growth and indicates that the wall assembly is not draining or drying properly (see Force below). Condensation also may indicate an imbalance in the HVAC system as well as inadequate ventilation, resulting in an indoor relative humidity that is too high and wall surfaces that are too cold. Even though this condition is found in wall assemblies, it is entirely independent of moisture infiltrating the building envelope. The combination of high humidity and cold surfaces allows water vapor to condense and creates an ideal environment for mold growth. The goal is twofold: One, to properly balance the HVAC system to keep relative humidity in check and provide adequate ventilation, and two, to allow the building envelope and wall assemblies to breathe. This allows water vapor to evaporate and the interior of the wall to dry.
• Force: What draws the water into the building or from one location to another is a key factor in determining its source and how to eliminate it. Investigators will look at gravity, capillary action, vapor flow and infiltration as a possible physical mechanism or force by which the water or vapor moves through the building. They also will look at how well the building is pressurized, especially as it pertains to moisture infiltrating the building. As the building envelope becomes tighter in an effort to save energy, the depressurization and pressurization of conditioned spaces is increased, which can lead to infiltration of moisture. At the same time, warm moisture-laden air can exfiltrate into wall and roof cavities. Moisture can become trapped and condense, thus creating an ideal environment for indoor mold growth.
Controlling Indoor Relative Humidity
One other significant factor for preventing indoor mold growth and building material degradation is to control the relative humidity in the indoor environment. In cold climates, moisture can collect in and on inside surfaces of exterior walls. When the inside surface of these walls becomes too cold, the surface relative humidity may exceed 65 percent or moisture may condense when the temperature at the inner surface of the external wall is at or below the dew point temperature of the room air. As discussed above, both instances provide a ripe environment for mold growth.
In warm climates, air-conditioning plays a key role. Indoor temperature and outdoor humidity conditions strongly influence whether and how much moisture may condense on or in the building envelope. Mold growth typically occurs on internal surfaces of external walls because the surfaces are cooled by air-conditioning to below or near the dew point of the humid air infiltrating into the envelope.
Preventing or solving water and moisture problems requires a strategic approach that begins at the design phase and is followed throughout a building’s lifecycle.
Article provided by Air Quality Sciences. Visit www.aqs.com to learn more or call (770) 933-0638 and ask for Building Consulting. Also visit Aerias to learn more about VOCs and other indoor contaminants. Access Aerias from the AQS website or at www.aerias.org. To learn more about GREENGUARD Building Construction Certification, visit the GREENGUARD Environmental Institute site at www.greenguard.org.
References
Committee on Damp Indoor Spaces and Health, Board on Health Promotion and Disease Prevention. 2004. Damp Indoor Spaces and Health. Institute of Medicine. The National Academies Press. Washington, D.C. Available online at www.nap.edu.
WHO Regional Office for Europe. 2009. WHO Guidelines for Indoor Air Quality: Dampness and Mould. World Health Organization. Copenhagen, Denmark. Available online at http://www.euro.who.int/document/E92645.pdf.
