02194nas a2200181 4500008004100000050001500041245007900056210006900135260003100204520156500235100002501800700002901825700001901854700002201873700002001895700002301915856007401938 1998 eng d aLBNL-4215100aState-of-the-Art Software for Window Energy-Efficiency Rating and Labeling0 aStateoftheArt Software for Window EnergyEfficiency Rating and La aPacific Grove, CAc08/19983 a

Measuring the thermal performance of windows in typical residential buildings is an expensive proposition. Not only is laboratory testing expensive, but each window manufacturer typically offers hundreds of individual products, each of which has different thermal performance properties. With over a thousand window manufacturers nationally, a testing-based rating system would be prohibitively expensive to the industry and to consumers.

Beginning in the early 1990s, simulation software began to be used as part of a national program for rating window U-values. The rating program has since been expanded to include Solar Hear Gain Coefficients and is now being extended to annual energy performance.

This paper describes four software packages available to the public from Lawrence Berkeley National Laboratory (LBNL). These software packages are used to evaluate window thermal performance: RESFEN (for evaluating annual energy costs), WINDOW (for calculating a products thermal performance properties), THERM (a preprocessor for WINDOW that determines two-dimensional heat-transfer effects), and Optics (a preprocessor for WINDOWs glass database).

Software not only offers a less expensive means than testing to evaluate window performance, it can also be used during the design process to help manufacturers produce windows that will meet target specifications. In addition, software can show small improvements in window performance that might not be detected in actual testing because of large uncertainties in test procedures.

1 aArasteh, Dariush, K.1 aFinlayson, Elizabeth, U.1 aHuang, Yu, Joe1 aHuizenga, Charlie1 aMitchell, Robin1 aRubin, Michael, D. uhttps://facades.lbl.gov/publications/state-art-software-window-energy01962nas a2200169 4500008004100000050001500041245010000056210006900156260003100225490001600256520135300272100002401625700002901649700002101678700002501699856006801724 1997 eng d aLBNL-4069000aThe Significance of Bolts in the Thermal Performance of Curtain-Wall Frames for Glazed Façades0 aSignificance of Bolts in the Thermal Performance of CurtainWall  aSan Francisco, CAc01/19980 v104, Part 13 a

Curtain walls are assemblies of glazings and metal frames that commonly form the exterior glass façades of commercial buildings. Evaluating the thermal performance of the bolts that hold curtain wall glazings in place is necessary to accurately rate the overall thermal performance of curtain walls. Using laboratory tests and computer simulations, we assessed the thermal performance of several different configurations of bolts and glazings. Curtain-wall samples were tested in the infrared thermography laboratory at the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California. Experimental results were compared to two-dimensional simulations approximating the thermal effect of the bolts using the parallel path and the isothermal planes calculation methods. We conclude that stainless steel bolts minimally affect curtain-wall thermal performance (approximately 18%) when spaced at least nine inches apart, which is the industry standard. Performance is increasingly compromised when there is less than nine inches between bolts or when steel bolts are used. We also show that the isothermal planes method of approximating curtain wall thermal performance can be used with 2-D heat transfer software typical of that used in the window industry to give conservative results for the thermal bridging effect caused by bolts.

1 aGriffith, Brent, T.1 aFinlayson, Elizabeth, U.1 aYazdanian, Mehry1 aArasteh, Dariush, K. uhttps://facades.lbl.gov/publications/significance-bolts-thermal