Volume 47, Issue 1 - January 2012


Improved Simulation Tools Help Users Optimize Energy Efficiency

Tools to evaluate facade design, such as COMFEN, provide a cost-effective and simplified solution to whole building energy analysis, said Sneh Kumar, manager of Department of Energy Projects at Traco in Cranberry Township, Pa., during a recent presentation.

Kumar was one of several speakers during the National Fenestration Rating Council (NFRC) presentation, "Key Tools for Commercial Window Energy Performance," at Ecobuild America in December, in Washington, D.C.

"Nonresidential buildings consume 15.5 quadrillion BTU of primary energy or 16 percent of all energy used in the United States," said Nils Petermann, project manager of Efficient Windows Collaborative in Washington, D.C. "Fenestration consumes 32 percent of that primary energy. On average, only 30 percent of all nonresidential buildings use high-performance windows."

Ray McGowan, senior program manager at NFRC, discussed the different NFRC tools available to determine fenestration energy properties. There are three kinds of tools, he said: fundamental, intermediate and advanced. Fundamental tools, such as Therm, Window and CMAST, and intermediate tools, such as COMFEN and Radiance, are used on fenestration components and systems, and advanced tools, such as EnergyPlus and DOE-2, are used on buildings and façades.

"The Therm and Window tools, used for residential products, have seen 95 percent manufacturer participation," McGowan said. However, he noted, "CMAST, used for commercial products, has had almost no certification and only 85 users in two years."

Kumar elaborated on COMFEN, developed by the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, Calif. "Fundamental performance indices of fenestration products-for example, U-value, solar heat gain coefficient (SHGC), visible transmittance, condensation resistance, air-leakage, etc.-are good for comparing products, but they do not provide information about the extent of impact on the building's annual energy, peak loads, daylighting, or thermal and visual comforts. Building designers need this information in order to select the most energy-efficient and cost-effective fenestration solution for their application."

COMFEN has come a long way since its initial versions, Kumar said. "This tool is being continuously improved by LBNL," he said. "Some of the impressive features of COMFEN are the daylighting and comfort evaluations built in COMFEN. It does daylight illuminance calculation to show the illuminance level in the façade boundary areas for a specific date and time. It takes into the account the effect of any overhand, fins, shading or attachments on daylighting, besides energy."

Thermal and visual comfort indices also are calculated for various design options, Kumar said. The COMFEN library has expanded with predefined façade component library, such as glazing, frame, wall, shading systems and spandrel.
-Sahely Mukerji

Industry Stands to Benefit from New DOE Determination
With the Department of Energy's (DOE) determination that the adoption of ASHRAE 90.1-2010 would reduce energy use by 18.5 percent compared to the 2007 version of the code, the market for high-performance glazing and framing systems looks poised to jump up.

In November, DOE officials announced that analysis shows that implementing the 2010 version of Standard 90.1, Energy Standard for Buildings, Except Low-Rise Residential Buildings, will save commercial building owners energy, help them meet sustainability goals and reduce carbon pollution.

"The DOE findings are aligned with the current glass and glazing industry trends of working towards more high-performance, energy-efficient products," says Urmilla Jokhu-Sowell, technical director of Glass Association of North America in Topeka, Kan. "The 2010 version of ASHRAE 90.1 incorporates the use of high-performance glass and glazing products and dynamic glazing, and also encourages proper daylighting design."

When DOE issues a final determination, states are expected to review the new code provisions and update their building code to meet or exceed the energy efficiency of the new standard within two years.

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