A front view of an iconic 1930's building with all glass windows — While transforming an iconic 1930s building into the Book Depository in Detroit, Gensler replaced all the windows with fixed double-pane, low-e windows that make the building more energy efficient. COURTESY ANGIE MCMONIGAL PHOTOGRAPHY LLC

June 19, 2025

Behind the Fine Art and Science of Glazing

Architects today are thinking beyond the curtain wall, using glass to deliver high energy performance and better comfort in a variety of buildings.

By: Justin R. Wolf

TRANSPARENT AND CLEAR, I GIVE SIGHT TO ALL. IN FRAMES OR IN BUILDINGS, I STAND TALL. WHAT AM I? The answer to this riddle is glass. The role of glazing in sustainable and healthy buildings is becoming clearer (pun intended) than ever before. On a basic level, windows provide views and daylight—two simple amenities that can be powerfully transformative for how a building feels to the people in it. But too much transparency can be a problem: Many progressive thinkers in the design community are moving away from the Modernist all-glass curtain walls that, while visually striking, have become beacons of inefficiency.

“The glass is the glass. It’s part of the skin [of the building]…. If your windows don’t have good connectivity to the surface, you’re going to lose air and heat in different places if it’s not built correctly,” says George Bandy, chief sustainability officer at Andersen Corporation. Bandy champions a “systematic approach” to glazing because the right design can contribute to optimal energy efficiency and building performance, better interior experiences, and reduced life cycle impacts.

inside the building with passage walkways on either sides and stairs going up from the foyer and the ceiling covered in glass. — Glazing can be a critical design tool for adaptive reuse projects. At the Book Depository, the Gensler team introduced an enormous 120-by-38-foot skylight that floods the atrium of the building with sunlight. COURTESY ANGIE MCMONIGAL PHOTOGRAPHY LLC

Glass As a Tool

The science behind glass production hasn’t changed a whole lot in the last few millennia. What has changed is how we assemble and design glazing for our buildings, as well as our understanding of how those things inform the building’s performance.

“Glass is a tool that needs to be used well,” says Heather Jauregui, director of sustainability for Perkins Eastman. The design firm’s work on the Boston Arts Academy, completed in 2022, features an orches- trated composition of triple-pane windows of varying scales. Jauregui describes taking “a rigorous approach” to optimizing window-to-wall ratios and assessing “where shading may be necessary.”

Interestingly, even with the cost premium of working with triple-pane glazing, Perkins Eastman managed to save its client $800,000 on the project. By reducing ratios and carefully sizing high-efficiency windows, the builders were able to drastically downsize mechanical needs as well. omitting perimeter heating entirely and only modestly relying on air-source heat pumps. All told, the school’s envelope cost more to build, but the resulting interior thermal comfort for students and faculty is largely achieved through passive means.

A sectioned facade of a building made in glass — The glass “Beacons” that protrude from the facade are a signature design feature of the Boston Arts Academy, designed by Perkins Eastman. But in fact, the architects’ judicious use of glazing saved the client money on the project. COURTESY ROBERT BENSON

Renovating an Icon

The question of glazing for building efficiency and occupant wellness becomes much more complicated in adaptive reuse projects. That was the case with the recently completed retrofit of Detroit’s Book Depository building, led by Gensler. The existing 1930s building, designed by Albert Kahn, has been described by Gensler design director Lily Diego as “an archaeological find.” (The connotations here are both good and bad.)

The square building’s deep floor plate, lack of insulation, and single-pane windows raised all manner of queries about how to create efficiency out of such chaos. “The building wasn’t built for human comfort!” Diego says. Making the Book Depository suitable for a variety of corporate tenants required some aggressive inter- ventions, like creating an entirely new entryway, while remaining mindful of the building’s historic character.

The Gensler team maintained the existing cadence of cleresto- ries but replaced each opening—about 120 in total—with fixed double-pane, low-e windows. To bring natural light into the building’s atrium and central corridors, the team introduced a massive 120-by- 38-foot skylight of fritted glass. Considering the choice to punch such a big hole in the roof, project architect Bruce Findling highlights how his team and their design partners conducted energy modeling to ensure “we were not only meeting [energy] code but exceeding it.”

University hall from the outside with energy effiecient glass glazing on the facade — Energy efficient glazing was a key part of LMN Architects’ strategy to help Founders Hall at the University of Washington exceed code on its performance. COURTESY TIM GRIFFITH

A Model of Sustainable Design

Seattle-based LMN Architects also had a mandate to exceed code with their design of Founders Hall, the newly completed 84,750-square-foot home for the University of Washington’s Foster School of Business. With it being the first mass timber building on the UW campus, reducing and sequestering carbon were key. LMN sought glazing strategies that revealed the exposed cross-laminated timber to outside observers and provided occupants with unimpeded views of the surrounding forest.

“We invested in a more expensive skin,” says LMN principal Robert Smith, while also mentioning that the building’s low energy use, smaller mechanicals, and low window-to-wall ratio (25 percent) allowed his team to get creative. Founders Hall’s double-pane, low-e windows are all operable, allowing fresh air to circulate, while the exposed CLT beams help regulate interior humidity levels. LMN kept things local by sourcing materials and services from local window manufacturer Herzog Glass, the Seattle office of Morrison Hershfield for facade engineering, and engineer PAE to conduct energy modeling.

An a frame made in wood and glass to show all the interiors of the house — Andersen’s A-Series windows are now offered with triple-pane glass, which helps keep more heat in and cold air out, allowing architects to design high-performance buildings. These windows use 14 percent precon- sumer recycled glass and have Indoor Advantage Gold certification for indoor air quality. COURTESY MEMORIESTTL

The Value of Durability

Looking ahead, Bandy is encouraged by building industry trends in which more players are seeking third-party indoor air quality certifications. He also notes the growth of what he qualifies as “extended” circular economies for decommissioned glazing products, the potential for windows to be built with more recycled content, and the importance of designing for longevity. “The most sustainable product is the one you don’t have to replace,” he says.

Would you like to comment on this article? Send your thoughts to: [email protected]

Latest

Viewpoints
Why Words Matter: The Future of Regenerative Design
As the design world embraces the language of regeneration, we must be clear about what the term means—and what’s at stake when it’s misused.
Profiles
Democracy Needs Room to Breathe
From reimagining Pennsylvania Avenue to reactivating Franklin Park, David Rubin and his Land Collective Studio are helping Washington, D.C. reclaim its public spaces as open, flexible, and deeply democratic.