Windows, step-by-step…

“Super-insulated houses require ultra-performing windows and doors.” That’s Passive House architect Christi Weber’s opening line regarding windows and doors on the “project overview” page of our Root River House site. “It would be pointless to work on the home’s envelope, only to cut a bunch of holes in it and fill them with low-quality, leaky windows and doors.”

To that end, we’ve invested a lot of time, energy and financial resources to ensure we meet Passive House benchmarks with this design. In the previous post, we asked Christi to elaborate on just what that means and how it works. In the post just prior to that (November 21), we saw the first several windows make their way from storage, into the house, and finally installed. In this post, a step-by-step look at the process.

“The devil is in the details when it comes to using European windows,” Christi goes on to say. “Unlike U.S. windows—where frame and sill are integral to the window, water drainage detailing is figured out, and nailing flange installation is easy—European windows require head scratching to think through these things.”

Indeed, there was some initial head scratching, but once Jeff and his crew got the hang of it, things moved along.  Here’s a close-up of the steps involved in the preparation and installation (click on the photos to enlarge them):


Above, Troy is taking the first steps by squaring up the rough openings, trimming excess exterior fiber board and the interior OSB wallboard. The opening is then lined with plywood (below, left) to provide the final squaring for the frame. Before the frames are actually set into the opening, key parts are covered by Grace Vycor ® Plus, a self-adhering flashing for sealing joints and seams (below, right).


For safety, 1x4s are mounted on the outside of the frame (below, left) to give the window a backstop of sorts when it comes time to actually slide the casing into place; at the same time, shims are added for the window casing to sit on during the leveling and centering. Once placed and centered, the casing is anchored with the first of several ¼” screws designed to hold the window in place (below, right).


After the first anchor is in, Jeff and JR (below) work slowly and carefully around the entire casing, adding screws while also watching that the casing remains centered and level. Finally, the window (sash) itself is set back on its hinges (below, center). The last remaining step is filling in between the window casing and the rough opening with spray foam insulation (from inside), backed by high density foam (wedged into the gap on the outside).


When all is said and done, the windows and their casings really do become ‘one’ with the house framing. They’re more solid than conventional installations and air leakage around the casing—or from the window inside the casing—will be virtually nil…and that’s an extremely critical goal in meeting Passive House standards related to unintended air exchange and winter heat loss.

As of today, all but one—the largest three-pane first-floor window—have been installed; the last one, along with the doors, will be installed once the ground floor installation has been completed.


    1. Yes, we sealed seams around all doors and window frames, both inside and outside. Inside was taped with Siga tape; on the exterior we used Vykor Plus—a self-adhering flashing.


Lanesboro, Minnesota
Climate Zone 6 (cold/moist)
Latitude: 43° 44' 18'' N
Longitude: 91° 54' 48'' W

House Size

Net Treated Floor Area: 1,514 SF
Gross Square Footage (House only): 2,210 SF

Building Envelope

Roof: R-99
Wall: R-61
Ground: R-53

Windows & Doors

Glazing: U-0.10 BTU / hour / sq. ft.
Solar Heat Gain Coefficient (SHGC): 0.48”
Frame: U-0.19 BTU / hour / sq. ft.

Modeled Performance

Specific Primary Energy Demand (Source Energy Demand): 12.1 kBTU / sq. ft. / year

Specific Space Heat Demand: 7.0 kBTU/sq. ft. / year

Peak Heating Load: 7,047 BTU / hour

Space Cooling Demand: 0.44 kBTU / sq. ft. / year

Peak Cooling Load: 3,625 BTU / hour

Pressure Test Goal: Whole House Air Changes Per Hour (ACH) = 0.4 ACH 50


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