Managing Moisture and Mold

By Ricardo Gamboa, Manager of Engineering and Technical Services, Johns Manville, Denver October 1, 2005

Important new recommendations have been set forth in the latest incarnation of ASHRAE’s 33-year-old Standard 62.1, Ventilation for Acceptable Indoor Air Quality.

The stated purpose for 62.1 is “to specify minimum ventilation rates and indoor air quality that will be acceptable to human occupants and are intended to minimize the potential for adverse health effects.” The standard applies to all indoor or enclosed spaces that people may occupy and it considers chemical, physical and biological contaminants that can affect air quality.

Several sections relevant to the HVAC industry establish new criteria, or fortify existing ones. Chief among them are those aimed at minimizing liquid water and the potential conditions for microbial growth in air systems. New attention has been given to the design, construction, operation and maintenance of air distribution systems—all equally critical factors necessary for providing a properly functioning system for the life of the building.

Significant new recommendations are given for controlling and managing the presence of water. Water management is vitally important for a number of reasons. When air systems properly limit water, fewer time-consuming callbacks are necessary to repair a faulty installation or to mitigate water damage. Also, litigation as a result of health issues or building damage can be minimized. But, most importantly, building occupants will be assured a safer and healthier indoor environment.

What 62.1 is not

It is clear the standard does not guarantee that adherence will provide absolute prevention of microbial growth from ever occurring; that is impossible. However, the new 62.1 presents measures designed to minimize the conditions that can lead to mold and mildew, ensuring water is kept to a minimum and is, therefore, unlikely to cause significant problems.

And, the standard’s recommendations are not product specific. Countless millions are spent each year on products aimed at solving the problem of mold and mildew growth, yet often nothing is gained for the investment. In fact, mold can occur on any material if water is present. Product and surface technologies, while essential considerations, are nevertheless secondary in importance to water management. The standard’s key focus, then, is not on finding the “holy grail” of materials, but on how one can best manage water in buildings.

Notable changes

Section 5.15.2, Condensation on Interior Surfaces , is one of seven new sections; this section recommends insulation for air ducts, pipes or other surfaces whose temperatures are expected to fall below the surrounding dew-point temperature, causing condensation to form. The insulation industry has known for years that insulating air ducts, pipes and equipment not only vastly improves an air-handling system’s energy efficiency, but also reduces the chance of condensation that can foster mold growth.

New section 7.1.5, Air Duct Construction , recommends that all air duct systems be constructed in accordance with accepted fiberglass construction standards, including several published by SMACNA and NFPA.

Section 5.6, Outdoor Air Intakes , has been greatly expanded from the former version and now includes five subsections related to the proper use of outdoor air intakes that are part of air ventilation systems. No longer concerned solely with air contaminants and pollution, the revised standard also addresses methods to minimize rain and snow intrusion through these air intakes.

Section 5.6.2 Rain Entrainment , recommends five procedures, including specifying air intake size, louver size, rain hoods and water drainage and/or removal devices. The revised standards also dictate that air-handling unit and other distribution equipment mounted outdoors must be designed to prevent rain intrusion into the airstream, whether in operation or not.

There is a new section in the standard, 5.11, Drain Pans , for constructing drain pans for collecting and draining liquid water, specifying slope, location and size of drain outlets; configuration of drain seal or P-trap; and pan size. Another, 5.14, Access for Inspection, Cleaning, and Maintenance , recommends greater physical access to ventilation equipment, including access doors and panels in ductwork and plenums. And, new standard 5.15, Building Envelope and Interior Surfaces , now recommends the building envelope be sealed to create a weather barrier that prevents liquid water penetration.

Putting 62.1 to work

ASHRAE recently issued a position statement with the objective of reinforcing the information in 62.1 and the need for minimizing indoor mold by managing moisture. In the statement, ASHRAE offers this sober warning: “Failure to address the impact of moisture in buildings is a frequent cause of mold proliferation in buildings… It is important to note that comprehensive moisture/mold management requires a three-phase approach: prevention, mitigation, and remediation.”

While some local jurisdictions might incorporate the revisions to 62.1 into their building codes quickly, others might not for months, even years. It is incumbent upon relevant professionals to understand well the revisions to their local codes and the timing of those revisions based on ASHRAE’s recommendations. These measures, when adopted into local code legislation, may add to the initial cost of systems and buildings. Yet they will lead to lower long-term costs for repairs and litigation due to the impact of liquid water inside the building envelope. And the greatest payoff is providing building spaces that are barriers to water, free of mold and safe places in which to live and work.