Jameson Simpson

The age-old challenge of stopping water infiltration before it starts now has the aid of technology and building science. Computer software, infrared thermography, wireless sensors, and moisture meters are joining the traditional standbys of flashing, weep screeds, and waterproofing membranes as tools that architects and builders can deploy.

Lest the digital devices take over, the conventional methods should not be overlooked. For stucco-finished walls, for example, metal weep screeds are critical, particularly at cold joints, to prevent water from sneaking behind the cladding, says Tom Reilly, AIA, owner of Thomas Reilly & Associates, Architects, in Prescott, Ariz. He notes that elastomeric paint, which installers often use to seal and finish the stucco, can actually exacerbate the potential for building damage by preventing water that gets in from getting out.

Meanwhile, roofer Brent Toggle, owner of Weather Resistant Contractors, builds every new roof with “the mindset that we’re going to have 5 feet of snow sitting on it,” he says. Based in Tulsa, Okla.—an area that has received unusually heavy snowfall in recent years—Toggle adheres to the following measures: pitching a flat roof toward a drain; flashing roof edges, valleys, and wall intersections; and applying a self-adhering membrane underlayment at roofing penetrations, valleys, and eaves—locations where melted ice and snow tend to refreeze.

These straightforward yet often-overlooked procedures are key in both new construction and renovation projects. However, designers must tailor these measures to their project’s specific site and climate.

Aside from experience and lessons learned from trial and error, architects and builders can now employ technology to pinpoint where and why a building is most susceptible to moisture infiltration. About 15,000 people have downloaded WUFI, a program created by Germany’s Fraunhofer Institute with the U.S. Department of Energy’s Oak Ridge National Laboratory. The full software package ($2,500, wufi-pro.com) helps users design residences to endure site-specific weather conditions. The tool calculates, on an hourly basis, the sensitivity and vulnerability of a building throughout the space based on the particular area’s exposure to environmental factors, such as wind, rain, sun, humidity, and temperature. WUFI also considers the fluctuating conditions of the residence’s interior, where occupants enjoy steamy showers, adjust the thermostat, and open windows.

The software helps identify which materials and installation practices will withstand weather- and occupant-generated moisture. Using data specific to the building and its environment means that the output will suit the project’s actual conditions, says Achilles Karagiozis, WUFI’s co-creator and Owens Corning’s global director of building science. “You don’t inject assumptions. You use actual loads.”

The software reveals how moisture, temperature, and other factors will affect every exterior wall of every room on every floor, Karagiozis says. The information enables users to examine the moisture-deterring metrics of each product they specify—and to become hyperspecific about which materials should be used. For example, instead of identifying only the R-value of an insulation product and leaving the material type and product brand to the contractor, designers could insist on glass-fiber insulation manufactured by a specific company, based on their knowledge of how well that product will perform in a wet environment.

Walpole, N.H.–based Bensonwood Homes is also investigating the effects of moisture in residential buildings, but its focus is on water that comes from interior sources. Because Bensonwood’s prefabricated timber-frame structures are virtually airtight, moisture from freshly applied interior paint, masonry, gypsum wallboard, and even sweaty subcontractors tends to linger inside. The trapped vapor can cause wood products such as flooring and trim to expand and contract, leading to excessive cracks.

Bensonwood partnered with student researchers from Keene State College. After Bensonwood’s panelized wall, roof, and floor system was in place, students using moisture meters and wireless sensors took hourly readings of water content, humidity, and temperature on interior and exterior building components throughout the construction of a home.

Bensonwood’s study concluded, in part, that poured concrete foundations, interior masonry work, and wet trades added enough moisture to cause wood to warp. Hans Porschitz, head of project management, says the research has led the company to experiment with techniques to speed up drying—through commercial dehumidifiers, for instance—and to introduce less moisture indoors, such as by applying two coats of paint instead of three. Bensonwood is repeating the study on a second home.

Pinpointing the sources of water and infiltration is essential for resolution and prevention, says home inspector William Decker Jr., owner of Chicago’s Decker Home Services. He uses infrared cameras to detect both air and water infiltration. The noninvasive technology is effective during construction and when homeowners ask for help in reining in energy bills, he says.

A thermal image, for example, may be able to pinpoint a wet spot on a wall stud because of the temperature differential, without requiring the wall to be opened. However, a contractor with a moisture meter may not be able to physically access such locations, Decker says. In his experience, he adds, leaky roofs and plumbing pipes are to blame about half of the time for stray moisture inside a residence. The other half stems from humidity entering the attic through exterior light fixture penetrations or a bathroom fan whose exhaust doesn’t make it outside.

Remodeler and designer Jeb Breithaupt, owner of Jeb Design/Build in Shreveport, La., says that finding a leak’s source can be challenging. He urges residential architects to inspect their projects throughout construction. “In residential, it’s rare for the architect to do the inspections,” he says. “But when you know [the builder is] putting the flashing up, say to the contractor, ‘I want to see the flashing.’ It’s one of the simplest things you can do.”

Karagiozis anticipates that incorporating building science and advanced technology in the quest for moisture control will eventually become mainstream. The fix that he recommends applies to students and professionals, alike: “Education, education, education.”