Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools

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While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving ... continued below

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Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie & Kohler, Christian September 11, 2008.

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While window frames typically represent 20-30% of the overall window area, their impact on the total window heat transfer rates may be much larger. This effect is even greater in low-conductance (highly insulating) windows that incorporate very low-conductance glazing. Developing low-conductance window frames requires accurate simulation tools for product research and development. Based on a literature review and an evaluation of current methods of modeling heat transfer through window frames, we conclude that current procedures specified in ISO standards are not sufficiently adequate for accurately evaluating heat transfer through the low-conductance frames. We conclude that the near-term priorities for improving the modeling of heat transfer through low-conductance frames are: (1) Add 2D view-factor radiation to standard modeling and examine the current practice of averaging surface emissivity based on area weighting and the process of making an equivalent rectangular frame cavity. (2) Asses 3D radiation effects in frame cavities and develop recommendation for inclusion into the design fenestration tools. (3) Assess existing correlations for convection in vertical cavities using CFD. (4) Study 2D and 3D natural convection heat transfer in frame cavities for cavities that are proven to be deficient from item 3 above. Recommend improved correlations or full CFD modeling into ISO standards and design fenestration tools, if appropriate. (5) Study 3D hardware short-circuits and propose methods to ensure that these effects are incorporated into ratings. (6) Study the heat transfer effects of ventilated frame cavities and propose updated correlations.

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  • Journal Name: Journal of Building Physics

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  • Report No.: LBNL-1022E
  • Grant Number: DE-AC02-05CH11231
  • DOI: 10.1177/1744259108097672 | External Link
  • Office of Scientific & Technical Information Report Number: 946732
  • Archival Resource Key: ark:/67531/metadc893884

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • September 11, 2008

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  • Sept. 27, 2016, 1:39 a.m.

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  • Jan. 4, 2017, 4:59 p.m.

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Gustavsen, Arild; Arasteh, Dariush; Jelle, Bjorn Petter; Curcija, Charlie & Kohler, Christian. Developing Low-Conductance Window Frames: Capabilities and Limitations of Current Window Heat Transfer Design Tools, article, September 11, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc893884/: accessed December 11, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.