Choosing Windows

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Windows for a passive house can actually function as "heaters" rather than heat losers. Choosing the right windows and locations are the key to making a passive solar home work.

Here's our research notes:
  • Design Considerations
    • Minimize the number of windows - for cost and energy efficiency.
    • Place them properly to allow for solar gain, view, cross-ventilation and stack effect air flow.
    • Fewer larger windows are more energy efficient than more smaller windows, because there is a higher glass to frame ratio with larger windows, and the frames are where the leakage occurs.
    • Allow for Window Coverings - Light blocking and have insulation value.  May cover some windows with foam for the winter.
    • South facing window to floor ratio of 9 to 12% - More thermal mass can allow for more south-facing windows.  
    • Keep windows 18 inches above floor to avoid safety glass requirement.
    • Passive house windows and doors weigh 2 to 3 times as much as conventional.
  • Window Construction:
    • Fiberglass, triple pane - makes sense once the wall reaches R-40 level (energy smart homes 2012)
    • Low U factor - Low U-value windows are important (from U 0.14 to U 0.23 as needed to reduce heat loss and maintain optimum comfort), but are less effective as the window area increases.
    • High VT (visible light transmission)
  • Windows selection changes based on wall direction:
    • South wall glass – high solar heat gain (at least .5)  with good interior shutters or shade with optional automatic sun control.     Appropriate overhangs for shading.
    • West wall glass – triple pane with low solar heat gain.
    • East and north wall glass – triple pane with standard solar heat gain and good window coverings.   Consider permanent covering in the winter - may allow for double pane glass.
  • Window Operation:
    • Mostly fixed picture windows for energy efficiency.  Eliminate screens from viewing area.  Awning and casement only where needed for air flow.
    • Casement on south and north sides allow to “scoop” wind typically coming off lake.  
    • Low awning windows on lake side to keep screens out of view line.  High opening windows on east side to allow for stack ventilation.
    • European style:  Tilt/turn style may consume some interior space and won’t catch the wind.   
  • Installation: The supplier may have specific instructions, but we like the video and article from FineHomebuildingon "Installing High Performance Windows".
  • Sources - We are not willing to import windows from Europe, need to find a local source:
    • Preferred:
      • Duxton:  www.duxtonwindows.com.  Made in Winnipeg, nice web site.
      • Accurate Dorwin:  www.accuratedorwin.com.   Made in Winnipeg.  Sold by Meteek Supply 4218 Enterprise Circle, Duluth, MN 55811, 218-722-7599, randy@meteek.com
    • Additional Suppliers:  
    • Inlinefiberglass.com (toronto), Paradigmwindows.com (toronto), Thermotecfiberglass.com (canada)
    • European only:  Wisconsin company:  http://www.wascowindows.com/WASCO_european_windows.html
    • European:  Optiwin has an office in Watertown, MN - imported from Germany
European:  Build it Like this:  EGE windows from Germany.   ege.de/en.   import directly for $845/unit plus shipping

    • Non Passive House Windows