The Department of Energy's Oak Ridge National Laboratory (ORNL) recently presented a new roof and attic system designed to reduce homeowners bills. At the heart of new roof system is a proprietary inorganic phase change material sandwiched between two reflective surfaces made of aluminum foil, which overcomes problems that have plagued phase change materials for the past 40 years.

"In the 1970s and 1980s the housing industry made several moderately successful attempts to use phase change materials," said Jan Kosny, Building Envelopes group, ORNL. "While these materials enhanced building energy performance, they were in many cases chemically unstable, were subject to corrosion or other durability problems and suffered from loss of phase change capability." Another shortcoming of some previous phase change materials was their susceptibility to fire. Fire is not a problem with the ORNL material, according to Kosny, who noted that ORNL researchers are working with leading manufacturers of phase change material on the development of non-flammable organic material.

Active thermal mass components, reflective pigments and coatings, subventing, radiant barriers and other novel techniques are being tested by a team led by Bill Miller and Jan Kosny of ORNL's Building Envelopes group, reveals the organization’s press release. Their prototype roof and attic system works by reducing attic temperatures by about 22 degrees Fahrenheit during a typical summer afternoon and decreasing the amount of heat that gets transferred through the attic floor to the living space. "The next generation roof will consist of infrared reflective materials that are dark in color yet reflect light as if they were white," Miller said. "In addition, radiant barriers and phase change materials will be integrated into a dynamic attic system that reduces utility bills for homeowners. The conservation strategies contribute on a much grander scale by lowering peak demand on utilities, reducing carbon emissions and, ultimately, they could lead to cleaner air."

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