Launch Slideshow

Setting Super-Windows in a Double Stud Wall

Setting Super-Windows in a Double Stud Wall

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    Designer and project manager Steve Daly applies Siga Wigluv tape to the edges of the window opening for waterproofing.

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    Applying Wigluv tape to the side jamb and lapping down over the sill tape.

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    Applying Wigluv tape to the head jamb.

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    Sealing the corner joint of the opening with a strip of Wigluv tape.

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    Operations Manager Evan Smith screws a temporary rail over the window opening to keep the window in place for leveling, squaring, and fastening.

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    Smith and Daly set a window into the opening.

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    Attaching a temporary stop block to the window buck to hold the window steady during leveling, squaring, and fastening.

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    Wedging the top corners of the window in place with shims.

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    Centering the window in the opening.

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    Setting the self-tapping, structural lag screw (supplied with the window unit) in place. Windows are pre-drilled at the factory to accept three lags in each side and two in the head rail. Plastic caps for the lag screws are also supplied.

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    With the tilt-and-turn sash open, Smith checks the hinge side of the unit for plumb ...

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    … then sends home the lower lag screw on the hinge side of the unit ...

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    … and checks for smooth tilt operation.

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    The window sill is checked for level ...

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    shimmed under one corner …

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    … then fastened with a lag screw through the pre-drilled hole on the strike side of the window.

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    After driving all3 screws on the strike-side jamb, lag screws are driven through the window’s head rail.

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    Taking down the temporary rail. The installed window is now ready for head flashing and trim.

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    A final check for operation--all done.

Last month, Coastal Connection stopped by a Roxbury, Mass., jobsite under construction by the innovative Boston firm PlaceTailor, where we got a look at an interesting solution to providing drainable, breathable strapping under the siding in a rain-screen wall assembly ( "Easy, Low-Cost, Drainable Strapping for Rainscreen Siding," July 22).

Last week, the European-made Schuco super-windows for the Passive House project arrived, and it was "all hands on deck" for a day while the project managers and crews came together on site to install 27 windows in three hours, says company Strategic Director and co-owner, Declan Keefe. "We have it down to where two people can set a window in about 20 minutes," says production manager and company co-owner, Evan Smith.

The design calls for the windows to sit flush to the outside sheathing of the drainable wall assembly. A system of bolts through the jamb makes setting the tilt-and-turn windows a simple operation: The crew screws temporary rails across the opening to keep the window from falling out; sets the window in place; screws temporary blocks to the inside buck jambs to hold the window steady; then opens the window to plumb and level the unit and set the supplied self-tapping lag bolts (see slideshow).

  • A set of framed window openings in the northwest corner of the two-family in-fill building in Roxbury, Massachusetts. Walls are 16-inch–deep, double-stud construction, with inner and outer walls joined with plywood gussets. Exterior sheathing and window bucks are ZIP System structural panels.
    A set of framed window openings in the northwest corner of the two-family in-fill building in Roxbury, Massachusetts. Walls are 16-inch–deep, double-stud construction, with inner and outer walls joined with plywood gussets. Exterior sheathing and window bucks are ZIP System structural panels.
  • Window labels call out the different solar gain characteristics and heat emission values for the window glazings used for different wall orientations and solar exposures. Higher solar gain windows are placed on the south side, while the east and west windows are chosen for reduced heat loss.
    Window labels call out the different solar gain characteristics and heat emission values for the window glazings used for different wall orientations and solar exposures. Higher solar gain windows are placed on the south side, while the east and west windows are chosen for reduced heat loss.
  • A crew member tapes the exterior window edge to the wall sheathing after the window is placed.
    A crew member tapes the exterior window edge to the wall sheathing after the window is placed.

The bolted connection also makes sealing the windows into the wall relatively simple: The crew tapes the outside edge of the window to the wall sheathing, fills the gap between the window and the framing bucks with expanding foam insulation sealant, trims the sealant flush on the inside and tapes the inside edge to the window buck.

The building, set on a heavily-shaded urban-infill lot in a wooded section of Roxbury, has limited solar exposure. It's also a two-family design (the lower unit has the entire ground floor and half of the second floor, while the upper unit gets half the second floor and all of the third floor). To make this design work, the building needs windows on all sides—the option of placing most of the glazing on the south side, typical in U.S. northern climate Passive Houses, wasn't practical. But Smith says that by selecting window glazing carefully, the designers were able to hit the required heating and cooling demand for the building (walls are 16-inch-deep double-stud frames, insulated with dense-blown cellulose). The south-facing windows on the street side of the house have a higher solar heat gain coefficient than the east-, west-, and north-facing windows. But this also means that the non-southern glazing has a lower center-of-glass U-value, making for a warmer wall during the heating season. Overall, says Smith, the windows provide the equivalent of an R-9 or R-11 wall in the glazed area of the building.