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By Nancy B. Solomon, AIA

An integrated solution

Fortunately, the conditions that lead to dampness and mold are generally understood by building scientists who study these phenomena, and strategies to prevent such problems are available (see resource table for helpful organizations and Web sites on page 178).

For architects to apply many of these strategies, it is critical that they become familiar with the natural flow patterns of air, heat, and moisture, which follow from basic laws of physics: Heat flows from warm to cold; moisture flows from warm to cold and from more to less (but, Lstiburek adds, “if these two are different, which is highly unusual, ‘more to less’ beats ‘warm to cold’ ”); air flows from higher to lower pressure; and gravity acts down.

Susan Doll, an associate at Environmental Health & Engineering, in Newton, Massachusetts, encourages architects to think about moisture dynamics: “Where does it come from—outside climate or interior activities (such as cooking, bathing, or even breathing)? And where does it go—into materials, air, or a condensation pan?”

To prevent mold from becoming a building problem, let alone a potential health menace, architects must minimize the amount of water—both in liquid and vapor form—entering a building, provide methods or details for it to be removed if and when it does enter, and specify materials appropriate to the moisture conditions. Appropriate strategies range from the obvious, such as sloping grade away from the structure and properly flashing all envelope penetrations, to the more obscure, such as thoroughly sealing the envelope with air barriers and creating consistent positive pressure throughout the building—even within wall cavities, ceiling plenums, and areas that house mechanical equipment—so outside air is not drawn in accidentally by the HVAC system.

Recognizing the multidisciplinary, multiphase, and regional variations of the moisture and mold problem, some clients who repeatedly build in different parts of the country are beginning to enlist moisture experts to monitor all facets of a project, from building envelope to mechanical systems, that affect building moisture at the various phases of design and construction. David Odom, senior consultant with Liberty Building Diagnostics Group, a building-forensics firm in Orlando, Florida, has worked with the Walt Disney Company, the U.S. Army, and now Harrah’s Entertainment, which is headquartered in Las Vegas but operates casinos around the country. As an independent consultant, Odom conducts design peer reviews that focus on building performance rather than initial cost, schedule, or constructability, which are already being considered by many other team members. He looks for problem areas and standard-of-care issues, as would an expert witness in a lawsuit. “We lead the team through that process when it is not adversarial,” says Odom. “By doing so, it forces everyone to better define how the building will likely operate once it’s constructed.”

And for those projects that don’t have the budget for this added layer of scrutiny, Gita Dev suggests that architects be more careful about which mechanical engineers they work with and pay more attention to construction administration. “The architect must be extremely demanding that details be met, and point out potential issues to the owner,” says Dev.