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Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
Highly Insulating Windows
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Highly Insulating Windows

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Presentation by Christian Kohler, Lawrence Berkeley National Laboratory …

Presentation by Christian Kohler, Lawrence Berkeley National Laboratory

On Thursday June 11th, the Alliance to Save Energy hosted a webinar for Alliance Associates and others interested in opportunities for window energy efficiency. Moderated by the Alliance’s Vice President for Programs Jeff Harris, speakers representing research, industry and low-income weatherization highlighted options that can minimize window heat loss far beyond common practice. The focus was on high-end R-5 window technologies, but lower-cost products, such as low-E storm windows, and the specific needs of low-income weatherization programs were also discussed. The five presenters’ different perspectives converged in the message that there is a great need for more energy-efficient windows and that advanced technologies and their integration in incentive and weatherization programs can bring far greater savings within reach.

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  • Transcript

    • 1. <ul><li>Highly Insulating Windows </li></ul><ul><li>Christian Kohler </li></ul><ul><li>Windows and Daylighting Research Group </li></ul><ul><li>Lawrence Berkeley National Laboratory </li></ul><ul><li>June 11, 2009 </li></ul>
    • 2. Windows and Daylighting Group <ul><li>10-15 researchers dedicated to windows research. Mostly DOE funded. </li></ul><ul><li>Engaged with industry since 1976 </li></ul><ul><li>State-of-the-art user facilities for testing and evaluation </li></ul><ul><li>Software used by over 8,000 users worldwide </li></ul>
    • 3. Performance Indices <ul><li>Key performance indices </li></ul><ul><ul><li>U-factor </li></ul></ul><ul><ul><ul><li>Thermal resistance </li></ul></ul></ul><ul><ul><ul><li>Units Btu/hr-ft2-F </li></ul></ul></ul><ul><ul><ul><li>R-factor is inverse, U=0.2, R=1/0.2 = 5 hr-ft2-F/Btu </li></ul></ul></ul><ul><ul><li>SHGC </li></ul></ul><ul><ul><ul><li>Solar Gains </li></ul></ul></ul><ul><ul><ul><li>Ranges from 0-1, higher means more solar gains </li></ul></ul></ul><ul><ul><li>VT </li></ul></ul><ul><ul><ul><li>Visible Transmittance </li></ul></ul></ul><ul><ul><ul><li>Ranges from 0-1, higher means more daylight </li></ul></ul></ul>
    • 4. Heat Transfer in Windows Conduction Radiation Conduction Convection Low-e coatings Special gas fills Multiple cavities Low conductance spacers Better frames
    • 5. Whole window metrices <ul><li>Whole product vs center of glass </li></ul><ul><li>Window components </li></ul><ul><ul><li>Framing (structural) </li></ul></ul><ul><ul><li>Glazing (vision) </li></ul></ul><ul><li>Frame area can be 25% of total area </li></ul><ul><li>NFRC and ENERGY STAR require whole product numbers </li></ul>
    • 6. Highly Insulating Windows - range Whole window U-factor 0.10 0.20 0.30 0.50 0.40 No heat transfer Standard double-pane windows Typical ENERGY STAR windows Highly insulating windows 0.35 = Northern ENERGY STAR benchmark
    • 7. Performance Goals <ul><li>Heating Climates: </li></ul><ul><li>static high solar, hi-R (U=0.1 Btu/h-ft2-F) can meet ZEH goals </li></ul>
    • 8. Benefits <ul><li>Areas near windows are often places of great temperature variation and discomfort </li></ul><ul><li>Conventional practice to avoid discomfort is to provide perimeter heating near windows </li></ul><ul><li>Perimeter heat may not be necessary with highly insulating windows </li></ul>Thermograms comparing a conventional dual-pane with a highly insulating window
    • 9. LBNL / DOE Research <ul><li>Triple glazings </li></ul><ul><ul><ul><ul><li>Develop lower-cost, non-structural center layers </li></ul></ul></ul></ul><ul><li>Spacer interactions </li></ul><ul><li>High Performance Frames </li></ul><ul><ul><ul><ul><li>Collaboration with European researchers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Focus on air leakage </li></ul></ul></ul></ul>2 sealed gas gaps at different temperatures and pressures with standard glass, unit is thicker and heavier low-e thin glass or plastic held by spacer spacer low-e only 2 paths for gas loss
    • 10. Highly Insulating Frames <ul><li>Mostly driven by PassivHaus Institute in Germany </li></ul><ul><li>5 Windows being tested and simulated in Norway and US </li></ul><ul><li>Verify performance with US rating criteria </li></ul>
    • 11. Low-e storm windows <ul><li>Pyrolytic Low-e coating (hard coat) </li></ul><ul><li>Does not degrade in non-sealed cavity </li></ul><ul><li>Identical installation cost to clear storms </li></ul>
    • 12. Savings <ul><li>Whole house heating energy savings over a winter season in Chicago for new storms: </li></ul><ul><ul><li>Clear storm windows 8-18% </li></ul></ul><ul><ul><li>Low-e storm windows 19-27% </li></ul></ul><ul><li>Estimated U-values: </li></ul><ul><ul><li>Clear storm windows: 0.49 Btu/h-ft2-F </li></ul></ul><ul><ul><li>Low-e storm windows: 0.36 Btu/h-ft2-F </li></ul></ul>
    • 13. Cost effectiveness – Low-e Storms Total Window Cost Annual Energy Savings Simple Payback (yrs) House 2- Low-E $1,738 $490 3.5 House 3- Clear $1,344 $111 12.1 House 4- Clear $2,661 $317 8.4 House 5- Low-E $1,738 $341 5.1
    • 14. Thank You Christian Kohler, CJKohler@lbl.gov Windows and Daylighting Research Group Lawrence Berkeley National Lab

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