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Fiberglass Windows Fit the Winchester Thurston School Bill

PostedbyPella Windows & Doors of Pittsburgh

on September 15, 2023


Project Scope

  • Type:


  • Industry:


  • Location:

    Pittsburgh, PA

  • Age of Structure:


  • Area of Structure Involved:

    Entire building

  • Products Used:


The intention behind renovating the Winchester Thurston Joan Clark Davis Center for Interdisciplinary Learning was to create a high-performance educational space, with the goal to get as close to Passive House performance as possible (although not seeking Certification). Therefore, the design of the window needed to include:

  • High performance with u-values between 0.15-0.17 btu/hr.ftsq.F
  • Units tall enough to fit existing openings without requiring additional units/mulling
  • Economical installation solution to work with complicated existing conditions

In order to achieve all of the fenestration goals, the Pella Impervia product line was recommended. The fiberglass window is a natural insulator due to the thermal properties of the fiberglass composite, providing u-values of .14 and .16 btu/hr.ftsq.F. The fiberglass composite material combined with a foam frame infill and triple pane glazing filled with Krypton gas worked together to deliver an extremely energy efficient product.

In order to provide an economical option, the fixed frame direct set, which can span 12' tall, was selected. The design of the units called for horizontal and vertical mulls, so a horizontal applied grille was utilized rather than increasing the number of mulled units since less units were required. An installation solution was developed, which combined a replacement method as well as an extension at the perimeter of the opening. The building is multi-wythe brick construction and originally the glazing was set in the brick. Since insulation was to be installed at the interior, which not only deepened the sill, but also moved the glazing further toward the interior, a large plane of brick needed to be covered. To fasten the window to the opening, the installation clip method was used. Blocking wrapped in metal trim was used to provide an extension at the perimeter of the opening.


  • Construction Partners: Architect: Moshier Studio | Builder: Lutz Briggs Schultz & Associates, Inc.

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