Green Building News

Green Building News March 2004

March 29, 2004

Moisture Myths Exposed

Each year American homeowners spend millions of dollars attempting to fix or prevent moisture-related problems. Too often, their efforts don't fix the problem. In some cases, these efforts actually make matters worse. So says Anton TenWolde, a physicist and researcher at the USDA Forest Service Forest Products Laboratory (FPL), who has been studying moisture in buildings for more than 20 years.

According to TenWolde, many generally accepted moisture-control practices in the United States are based on limited or no research but mostly on tradition among home builders and others.

“We spend very little on housing research in the United States. Several countries, including Canada and even smaller nations like Denmark, the Netherlands and Sweden, invest more than the United States in research into home-building technology,” he says.

The problem of basing home construction or repairs on unproven building practices is amplified because some of those traditional practices have become part of building codes around the country, TenWolde says.

According to TenWolde, building codes historically deal with safety issues such as fire prevention, electrical safety or structural standards. Building codes sometimes go beyond safety when they try to deal with moisture.

“And moisture is one area where current building codes get it wrong, especially when they apply standards that might make some sense in northern Maine or Minnesota to Florida or Texas,” TenWolde says.

TenWolde identifies five main ideas about home construction and maintenance that are widely misunderstood or downright incorrect. He calls them “The Five Myths of Moisture.”

Myth One concerns so-called vapor barriers, or vapor retarders. “A vapor retarder, normally installed only on exterior walls, is intended to slow the diffusion of moisture from an area of higher humidity to one of lower humidity. Such barriers are ineffective if there is any air movement, which is almost always the case in wood-frame construction. An air barrier, to be effective, needs to envelop the entire house -- ceiling and floor as well as walls,” TenWolde says. “Problems caused by diffusion are very rare; moisture problems caused by moving air are much more common.”

In warm, humid climates, a vapor barrier can do harm. Nonetheless, practically all building codes require vapor barriers or retarders. (Vapor barriers originated in the 1930s, partly based on research conducted at FPL.) A more effective approach to controlling moisture intrusion would be to make the house as air-tight as possible and provide good drainage around the house, according to TenWolde.

Myth Two is that attics need to have lots of ventilation. Again, venting requirements are not based on rigorous scientific research. TenWolde explains that attic venting originally arose as a moisture-control strategy for cold climates. Other purported benefits, such as longevity of the shingles, arose later. It is widely believed that increased attic venting will prolong the life of roofing shingles by cooling them. But research shows that venting has very little, if any, effect on shingle temperature. The most important issue in shingle temperature appears to be the color of the shingles. Light-colored shingles reflect sunlight and don't get as hot as dark shingles.

One possible real benefit of attic venting in climates with large snowfalls is to reduce snow melt on the roof to avoid the formation of ice dams. But according to TenWolde, a more effective—and energy-efficient—way to control snow melt in almost all climates in the United States would be to use air barriers and insulation to prevent heat from entering the attic.

Myth Three is that new homes are built “too tightly” and that walls have to “breathe.” That is the reason often given for the presence of mold in newly built houses. TenWolde cites recent research in Canada that revealed that houses that leaked air had as much, or in some cases more, mold than tight houses.

“It takes very little air movement to accomplish drying, and even a house with good air barriers usually will permit enough movement to permit moisture to escape, unless there is massive water entry. Uncontrolled air movement may actually cause moisture problems, and certainly can cost money in air conditioning and heating,” he says.

Myth Four says that crawl spaces need to be vented. To TenWolde, venting crawl spaces is just as dubious a practice as venting attics. Venting crawl spaces is marginally effective in dry climates but can be harmful in wet or warm humid climates. The best way to control moisture in crawl spaces is to use site grading, downspouts and soil covers to prevent water from entering the crawl space.

Myth Five is the belief that building codes actually address residential moisture problems.

“Building codes address only vapor “barriers” and venting attic and crawl spaces. These are only two ways of controlling moisture and not very effective ones at that,” TenWolde says. “Most real moisture damage in homes is caused by water entering the home through leaks or poor flashing details. The most effective practices for controlling moisture are related to proper installation of windows, flashing, site grading, foundations, rain absorption, roof overhangs, and whole-house ventilation and humidity control.”

TenWolde’s “Five Myths” reflect the fact that there is considerable confusion and misunderstanding around moisture problems. In an attempt to resolve some of those differences and publicize the latest research findings, the FPL has joined with industry-related organizations to establish a Residential Moisture-Management Network. The network will evaluate existing research and develop uniform recommendations for dealing with moisture.


Habitat House Avoids Vinyl, Attracts Controversy

New Orleans Area Habitat for Humanity, GreenPeace and other groups have begun construction on a house without polyvinyl chloride (PVC or vinyl) material or other toxic household products. As a major sponsor of the project, GreenPeace hopes it may serve as a model for Habitat homes and affordable housing around the country.

"Like homelessness, pollution is a global problem -- one that disproportionately affects the poor and communities of color,” said John Passacantando, Executive Director of Greenpeace.  "This house will be a testament to two basic human rights:  the right to decent housing and the right to a healthy environment.

The PVC-free Habitat house is the first project of its kind for Greenpeace, known for its high-profile acts of civil disobedience to draw attention to environmental issues. Already, the house is causing controversy.  In late February, the Vinyl Institute, the trade association of vinyl manufacturers, wrote to Habitat for Humanity International, criticizing the New Orleans affiliate for working with Greenpeace on this project.

Greenpeace wants to demonstrate that it's possible to build a $55,000 home without vinyl, and plans to make a video and report of the project to give to other Habitat chapters and those interested in low-income housing. The house will use affordable alternatives for vinyl that are widely available. Also, the floor system of the house will be built with wood that is not treated with arsenic (which, until recently, was commonly used as a preservative) and that is certified as sustainably harvested.  All of the power needs for construction are being provided by Greenpeace's "Rolling Sunlight," a mobile solar-powered generator.  

Louisiana has the greatest concentration of PVC facilities. Toxic pollution from PVC plants has displaced entire communities and disproportionately affects low-income and predominantly African-American towns. 


USGBC Considers Accepting Trade Associations as Members

The green building movement's most prominent organization is grappling with an issue that may define its development for years to come: whether to accept industry trade organizations as members. Individual companies, including material manufacturers, are already allowed to join. However, some members are concerned that trade associations would exert undue influence on the direction of the organization. The Vinyl Institute, American Forest & Paper Association and other groups have requested membership.

When an unpleasant public relations issue appears, individual companies often distance themselves while relying on their trade association to represent their interests. Opponents of the move to allow associations USGBC membership fear that the financial and staff resources of well-heeled trade groups will steer USGBC toward industry-friendly positions and away from its environmental roots.

Opponents of the idea include many current USGBC members. A draft response from to the USGBC's Board Task Force on Trade Associations report includes this statement:

"We are convinced that trade associations pose a clear danger to the mission and purpose of USGBC. Their primary mission is to protect the economic interests of their constituents. This places them at odds with USGBC’s mission of promoting market transformation toward sustainability. Indeed, the actions of numerous trade associations confirm their opposition to LEED. The board would make a fatal mistake if it allows these organizations to join USGBC. Instead, we urge their exclusion and recommend that the Council instead establish a continuing dialogue with trade associations to involve them in USGBC activities."

While trade associations lobby for acceptance, environmental groups are actively opposing the idea. A page on the Healthy Building Network Web site called "USGBC Grapples with Trade Association Challenge" provides links to information and ways to express your opinion.


Green Remodeling Guides

Most of the excitement around green building focuses on new construction. But many people interested in being green, just don't have the resources to build from scratch. Recognizing this, sustainable building advocates at the City of Seattle have developed a series of green remodeling guides in PDF format. So far, they offer guides on kitchens, bathrooms and roofing. Guides on paints and finishes, landscaping and hiring a professional are planned.


Zero Energy Remodeling Project

The idea of a Zero-Energy house (one that creates more energy than it consumes over the course of a year) has, so far been limited to new construction. That's about to change.

An energy-efficient restoration project on a 24-acre Victorian farmstead in Lebanon, NJ, is expected to produce the nation’s first rehabbed zero-energy home, according to comments by Bill Asdal, president of Asdal and Builders  of Chester, NJ, at the National Building Museum in Washington, D.C. last month.

Asdal’s company is working with the NAHB Research Center  through the Department of Energy's Building America  Program for Existing Homes to restore a 19th century, two-story, 1,500-square-foot home that will serve as the innkeeper’s residence in a bed and breakfast project. The remodeling research initiative also includes a 4,000-square-foot Victorian home, a garage and a barn.

The project uses readily available renewable energy systems that produce electrical and thermal energy, including photovoltaic roof panels, an active solar hot water collector and geothermal heating and cooling. With the exception of liquid propane for a fireplace, no fossil fuels will be used in the two houses, he said. “Consistently, we waste wind, we waste sunlight and we waste water,” Asdal said, describing underutilized energy resources that are being tapped for his project.

The annual net energy use of the smaller test home is now predicted to be zero over the span of a year. Current demands on the system are light, and the building is operating as a residential power plant, metering a negative 185 kiloWatt-hours of power after its first month of operation.

A careful analysis by Research Center engineers of the acquisition and installation costs of the energy-efficient features versus their operation and maintenance costs suggests that there will be a double-digit return on investment for the technology that was selected for the project.

Microprocessor controlled ventilation, air-sealing techniques, blown cellulose insulation  and energy-efficient appliances are other technologies included.

As it becomes increasingly difficult to find places to build housing, Asdal predicted that the emphasis on retrofitting the nation’s 116 million existing homes will steadily increase. “The streetscape will look very much the same in 10 years, 50 years or more,” he said, but the homes themselves hold the potential for dramatically improving their energy efficiency.

Good systems and responsible behavior could easily cut in half the costs of operations and maintenance, which are the only costs associated with owning a home that the consumer can control, he said. (Source: Nations Building News)


Magnetic Ballasts Dodge Regulatory Bullet

New regulations from the U.S. Department of Energy were intended to eliminate older less efficient magnetic ballasts needed to drive linear fluorescent lights. This assumption -- widely held among the lighting industry -- is now open to question. Advance Transformer, who manufacturers this product recently told DOE officials that its magnetic ballast will pass the new standards when used with 34-Watt, T12 fluorescent lamps. This combination is widely used and account for as much as 75 percent of all four-foot fluorescent sales. As it turns out, the regulations scheduled to take affect next year will have no effect in reality.


Housing Research Gains Momentum

The National Science Foundation (NSF) -- long known as a guiding force in basic and applied science -- has become involved in housing research. Through a partnership with the Partnership for Advanced Housing (PATH) program NSF has opened the door to more vigorous and focused research through American universities.

"The NSF-PATH partnership has broken new ground in housing research," said Dana Bres of the Office of Policy Development and Research of the U.S. Department of Housing and Urban Development. "Prominent universities across the nation are examining diverse housing issues ranging from process improvements and product innovations to systems integration and beyond."

Particularly exciting to PATH and gaining worldwide attention is the extraordinary "instant house," also referred to as the "cake-mix" house. Dr. Behrokh Khoshnevis of the University of Southern California presented the home building technique that will make it possible to build a house from foundation to roof in less than 24 hours.

"Automated Construction by Contour Crafting" consists of robots that deliver concrete through a jet.

"NSF's partnership with PATH to stimulate housing research was, in fact, a groundbreaking direction for the National Science Foundation -- its first major research initiative focused on housing," said Dr. Perumalsamy N. Balaguru, program director of NSF's Division of Civil & Mechanical Systems. "Before NSF became involved, housing research did not command a high priority within academic institutions and many committed university researchers and professors struggled to gain a foothold in the area."

PATH's partnership with NSF has raised housing research to a new level and has attracted attention and resources to this much-needed work. One of the largest hurdles for the housing industry is determining the most effective way to cut development time to market. Theodore Koebel, director of the Center for Housing Research at Virginia Tech and lead author of PATH's "The Diffusion of Innovation in the Residential Building Industry," discussed the substantial social, economic, and environmental benefits associated with the diffusion of innovation in the residential home building industry.

"Together, we have successfully awarded 33 grants to 21 principle universities since this program began in 2000 -- a noteworthy accomplishment," said Bres.

"With each discovery and recommendation, the potential uses in further research and industry development should be considered," said Bres. "The question that the housing industry must ask is 'What's next for this research?' Let's keep these exciting results from gathering dust on a shelf -- or on an isolated hard drive."

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