• Can I use these triple-pane vinyl windows for my Passive House, they’re a lot cheaper…

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  Sep 27

  I reran the 2010 “Design Boundaries” study in Portland Oregon climate, for 3 different window performance levels, to get an idea of how much the design space is constrained by not using Passive-House-grade windows, which one might be tempted to do based on current cost difference.  (This does not take into account the lower interior comfort effect of cheaper windows, nor any added air-sealing risk.)

  As in the 2010 study, the things that are held constant are the R-values of the walls (66) , floor (71), and roof (89), the HVAC and appliance efficiencies and so on.  The windows are a standard 3×5 feet.  The things that vary are the length and width of the building, number of stories up to 4, orientation, site solar access, and the window-to-wall ratios on the North, East/West, and South.  Altogether 18432 cases are generated and automatically run through PHPP.  The results can then be filtered to see how many cases meet the Passive House performance criteria, and what are the easiest and toughest cases.

  The three window performance levels (all triple-pane) were:

  • Optiwin (Passive House certified window from Germany)
  • vinyl with high solar heat gain glass e.g. Cardinal LoE 180, and
  • vinyl with low solar heat gain glass e.g. Cardinal LoE 272.

  From some angles the situation doesn’t look too bad, but when I restricted it to 4-person houses (1300-1700 sf of Treated Floor Area), there were 10 times as many Passive House cases with the good windows than with the not so good.   To save that window money you’ve got to accept some design constraints is the upshot.  Here’s some charts:

  Window-impact-on-PH-design-boundaries.pdf

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