Building Science Could Succeed Where Traditional Construction Has Failed in Preventing Home Scourge
by Julie Bonnin
For years, experts in building science—the technologists of construction—have predicted that changes in materials and improper and outdated installation techniques, among other factors, would eventually cause widespread mold problems for homeowners. However, word rarely filtered down from the researchers with doctorates to the guys in the pickups doing the work, said Doug Garrett, president of Central Texas-based Building Performance & Comfort.
But as concerns about mold have grown, builders have turned to building science for answers. Preventing this costly problem likely will require a new approach to house building.
Garrett is a frequent speaker on the topics of moisture management and air quality and a member of the Texas Department of Health’s mold policy committee. Audiences such as the air-conditioning contractors he spoke to recently are hungry for such information.
“I finished speaking at 12:15 and they were still asking questions at 1:30,” he said.
Garrett is among those getting the word out on how to stem the swelling tide of mold problems in homes and other buildings. He and Terry Brennan, a New York-based air-quality expert who also has advised the Texas Department of Health, were among those who spoke at the International Green Building Conference Nov. 13-15, 2002 in Austin.
With Joseph Lstiburek (pronounced stee-brook), a forensic engineer who is one of the world’s foremost experts on energy-efficient construction, Garrett and Brennan are busy advising contractors, architects and others on how to do things right when it comes to designing and constructing buildings.
What’s gone wrong is a combination of factors, they say.
Some building materials in widespread use—paper-covered gypsum board, cellulose ceiling tile, particle board and others—happen to be great food for mold, which can grow wherever moisture accumulates.
Other materials that are in widespread use—fiberglass and cellulose cavity insulation, polyethylene vapor retarders, vinyl wallpaper—make it harder for walls to dry out.
Add tight windows and other features designed to boost energy efficiency, and the lack of air flow creates moisture problems.
Houses have always leaked, Lstiburek said, “but that incidental water didn’t mean much because the building dried so quickly. Now we have to choose different techniques to install windows and doors.”
Another factor, he said, is “cold climate chauvinism” in nationwide building codes: Many good building practices for northern climates have been enforced in places such as Texas, even when they didn’t make sense for the state’s hot and humid climate.
Thousands of homes built in Austin in the 1970s and ’80s, for example, were built with a “vapor barrier” consisting of a sheet of plastic stapled underneath the drywall. Vapor-proofing was designed to keep moisture out of walls in the North, but in the South, it works in reverse.
Water vapor moves from warm to cold and from wet to dry. In the North, that warm, moist air is on the inside of the house, and the vapor barrier serves to keep it from infiltrating the walls. In the South, the warm, wet air is on the outside, trying to move inside, and the vapor barrier effectively traps the moisture within the walls.
The vapor barrier was the perfect place for mold to grow, fed by condensation caused by humidity in the air, Garrett said. The building code requiring the vapor barrier in most parts of Texas was changed last year, he said.
Although some have accused builders of cutting corners and not allowing materials to dry properly as they hurried to meet the housing boom, Garrett said that is less of a contributing factor to problems with mold than the trend toward building complicated structures.
“A lot of the houses having the worst problems are the large custom-built homes,” Garrett said. “The bigger the house, and the more roof angles you put into a house, the more difficult it becomes to do a decent job. When you have lots of complicated details—curved walls, huge walls that are mostly windows—it’s no wonder you have problems.”
All of the discussion about mold has been tracked closely by the Texas Association of Builders, which will propose legislation this year that would put a tighter rein on the state’s building standards.
The group has also been working on a building guide with tips for preventing mold in homes, video training guides for construction workers, and recommendations for going beyond building-code standards when necessary, said Kristi Sutterfield, executive vice president of the organization.
The association also is working on a homeowner responsibility checklist that would be distributed to new homeowners when they close on their home.
“This (mold prevention effort) is the biggest undertaking we’ve taken on,” Sutterfield said. “We’re recognizing that we need to get in and roll our sleeves up and provide homeowner education, builder education and have more input into the government regulation agencies that play a part in all of this.”
Ryland Homes is one of several area home builders that try to use some of the new building techniques.
Ryland builds houses using a program it calls HouseWorks, which uses many of the building science techniques recommended by the nation’s top construction experts to prevent mold.
Key to the program is making sure that the plumbing system, the heating and air-conditioning system, insulation and thermal envelope of the house—the windows, doors and siding—all work together, said Randy Erwin, energy program director for Ryland Homes.
It might sound like common sense to have everything working as a system, but traditionally, construction of many homes is done piecemeal, with separate contractors installing such things as plumbing, heating, air conditioning and roofing with little regard to how they all work together.
Ryland brought in experts who trained subcontractors and superintendents, and developed an inspection team. Sales people also had to be educated about how to sell the new homes.
Although there are added costs to running the program, Erwin said: “It’s not so much the cost that deters (other) builders, it’s that it makes it much more complicated.”
But it’s worth the trouble, Erwin said.
“Our warranty claims have dropped substantially,” he said. “We know we’re having less problems with homes. It’s a lot easier to do it right the first time than to retrofit something.”
Close to 2,000 architects, engineers and other building professionals attended the Green Building Conference in Austin last November. This was the first in a series of such conferences.
Reprinted from the October 19, 2002 Austin American-Statesman. Julie Bonnin is a freelance writer and editor in Austin, Texas.
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