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Green Building News

PHIUS Posts Window Data

The Certified Data for Windows program includes recommendations for different climates zones for those seeking Passive House certification

PHIUS shares window data. This is the kind of information on window performance you'll find at a website offered by the Passive House Institute U.S.

Passive House Institute U.S. has posted detailed performance data about windows online for ready access by builders and designers.

The Certified Data for Windows program is organized by manufacturer, and includes key values such as the window’s solar heat gain coefficient, its center-of-glass U-factor, and its whole-window installed U-factor.

Each window description also includes recommendations on which climate zones and which orientation the window is best suited for. There’s also a link to a THERM file that a Passivhaus planner would use in energy modeling software.

PHIUS has been working on the program since the fall of 2012, but posted the data to its website only last week.

In a March 28 post explaining the program, its manager, Graham Wright, said, “PHIUS’s window program is moving toward a critical goal: producing data in the format that passive house consultants need, and that enables direct comparison to windows rated by other [European]-based outfits like PHI [Passivhaus Institut] or say IFT Rosenheim. Both window industry representatives and passive house designers have told us this is critical if we want to energize the market.”

While the PHIUS system makes climate-specific recommendations for different windows, Wright says it’s his understanding that the German-based Passivhaus Institut is “still pass/fail at one level.”

“Going forward,” he said, “if you hear, ‘This is a passive house window,’ people should know to ask: ‘For what climate?’ Be wary of claims about passive house windows that don’t show any numbers or label or certificate. It might just be loose talk.”


  1. jackofalltrades777 | | #1

    Makes More Sense
    It makes more sense to certify a window based on the climate zone, not just a PASS/FAIL type of system rating. A south facing window that is Zone 6 appropriate might make a home overheat in a Zone 4 climate. One size doesn't fit all here in the USA since we have such a vast terrain that incorporates all types of diverse climate zones not seen in Europe.

    It does show a whole window U-Value, which is nice since it can be matched up better with the US based systems. Nice to see energy efficient windows like Intus with U-Values < 0.20 but don't cost an arm and a leg. I've seen many projects here on GBA that used them.

  2. wjrobinson | | #2

    Me stupit.... posted info... I see nuttin for zone 6, 7 or 8 south facing. I see no costs... what the heck is you talking about... blogster... and Peter... Point me.

  3. GBA Editor
    Martin Holladay | | #3

    Response to A.J. Builder
    Several of the rated windows are recommended for Zones 6, 7, and 8, but only for use on the east, west, and north sides of buildings. None of the rated windows has yet met PHIUS's criteria for use on the south side of a building in Zones 6, 7, and 8.

    Just because window manufacturers have not yet created a window meeting some of PHIUS's criteria, does not mean that the data aren't useful.

    The PHIUS web site does not include cost data. Neither PHIUS nor our reporter (Scott Gibson) claimed that it did.

  4. Bronwyn Barry | | #4

    aj builder spots the snaffu
    aj builder may have spotted a snaffu in the PHIUS data sheet... (It would be odd for a window to qualify for the 'off-south' elevations and not the south one.) Hopefully Graham will fix that soon?

    Great data otherwise, and very revealing. What it tells me is that Zola - one of two imports on the current list - has the only windows that currently qualify for a PHIUS+ house in zones 5, 6 & 7. (Canada & Alaska - you're relegated to frost-bite-city.) It means that the Marvin window included on this list couldn't be used in a PHIUS+ House in northern Minnesota where it is made. It means you can only use the Alpen 925 fixed window for the Zone 6 parts of Colorado, where it is made. And it means that our local building industry must demand better performance numbers from local manufacturers before we finally emerge out of the Product Dark Ages.

    Graham Irwin recently shared this quote from Kevin Surace of Serious Energy at our Passive House California Annual Conference: "Dual pane windows were invented back in 1865. So in 1870, they were truly best of class. But I'm thinking, 140 years later, and we call that energy efficient?" So come on North America - you know you can do this!

    For those who are curious to see current 'best in class' window performance data (including a growing number from North America) check out this list of Certified Passive House windows: There are additional fixed ones listed separately here:

    For those interested in understanding how the data for all these window programs is calculated, I offer a comparative analysis here:

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