EARLY QUESTIONS TO INFORM LATER DECISIONS

Commentators advocate attention to the end of systems’ life cycle, beginning at the early stages. “More projects are asking that question,” notes Deo: “How can we be more responsible [and] forethink what we can do to facilitate the recyclability of what we are creating? There is more attention being spent in terms of the front end of the project, where we are deciding material composition, ethical sourcing, and sustainable sourcing alternatives.... Lesser attention is being paid to what happens after the life cycle.” He imagines “a metric that comes in place that measures that capacity to be recycled; that parameter I do not think exists, but would be worthwhile.” He envisions a score system for materials’ recyclability, though “that hasn’t really evolved to that level in our day-to-day course at this stage.”

Some situations are a matter of choice among parallel standards. On a recent project at Princeton University, Deo recalls consulting “the Design Standard Manual, which is higher than code requirement for performance. We also tested Passive House, and what we found was that the source of energy for the campus was so cheap that the payback period was way too long to make a rational decision to go Passive House.... So we went in the direction of the design standard that they already had in place.”

Codes in Boston, New York, and similar cities, Deo finds, are driving performance and sustainability, in some cases “very compatible with a non-curtain-wall enclosure” with punched windows; with curtain walls, “there are multiple trades that will be operating in the field assembling that wall together, and there is a little bit of a higher risk of failure where the interfaces are going to increase between those two trades. What we need to push for is less prescriptive on the system standpoint, more prescriptive from the performance standpoint.”

Aluminum and other metallic components are generally valuable at the scrap stage, Patterson notes, and finishes on metal (unlike those used for glass) burn off in the recycling process, so that a high proportion (though not 100 percent) end up recycled. A persistent obstacle to facade-component recycling, however, is that bespoke components are harder to reuse than standard ones. “This aspect of reuse is certainly exacerbated by the lack of standardization in buildings and facade systems,” he says. “If you look at all of the high-profile buildings being built in New York City, what’s really driving those is aesthetics.

“There’s a lot of exploration of geometric complexity in the facade system, so instead of the old days, where you’ve got big planar orthogonal surfaces, you’ve got all these articulations in the building skin, and you end up with a lot of different sizes in the glass or the metal panels and reuse is most often really out of the question. The most you can hope for is that the materials are reclaimed and recycled, and it’s not like it’s free once it’s recycled; there’s an energy cost and a carbon-emissions cost in recycling those materials.” The logical implication is that design facilitating disassembly will be an increasingly important corollary of design for durability.

CONCLUSION

Addressing the typical tradeoffs among the different priorities a curtain wall serves—occupants’ comfort and experience, operational and embodied carbon impacts, architectural expression, and owners’ short-term and long-term economic expectations—the environmental design consultants at Atelier Ten offer practical strategies that are best implemented early in the planning and design stages. “First, list all factors, prioritize them if possible, and use different design moves to solve for different performance criteria,” says Emilie Hagen, director of Atelier Ten’s San Francisco office. “It’s possible with thoughtful design to make ‘performative exterior shading’ (which helps with glare and operational carbon reduction) or other facade moves also part of the architectural expression. Its embodied carbon also has a shorter payback. Similarly, avoiding exterior shading where it doesn’t provide performative benefits and only serves an architectural purpose can be rethought to minimize embodied carbon while still making an aesthetic statement.”

A second step, Hagen says, is to “set project-level goals, so you can trade off between the facade and other parts of the building.” Her third recommendation is to “quantify whichever performance criteria you can through analysis, and lay out key metrics for each in a comparison table to help decision makers. While most performance criteria for facades are not inherently comparable to each other, evaluating each design move by seeing how much it moves the needle for each criterion is helpful for holistic evaluation.”

Owners can make more responsible decisions when they recognize that short-term cost cutting is usually a euphemism for shifting costs onto the Earth. Design and specification decisions are more responsible when they account for maintenance and envision the full lifespan of the building, including deconstruction and recycling in a circular cradle-to-cradle process. Patterson’s observation of “wasted durability” in many current facade systems implies that design and construction teams might bear a converse concept in mind: “coordinated durability,” a condition where the longevity of components is known or monitored, maintenance responds to local signs of degradation before they lead to more general failures, and a building envelope’s service life matches that intended for the building as a whole.

WORKS CITED

¹Hens I. Life cycle impacts of timber unitized curtain wall. M.S. thesis, University of California, Berkeley, College of Environmental Design, 2021, https://drive.google.com/file/d/14y5KNIiA7j_gX0OysH8K_rb4kAP-3wVP/view.
²Hens I, Schleicher S, Pennetier S, Schiavon S. Life cycle impacts of timber unitized curtain wall. Center for the Built Environment, 2022, https://cbe.berkeley.edu/wp-content/uploads/2022/04/03-Lifecycle-timber-curtainwall-04-22.pdf.
³Patterson M, Silverman B, Kensek K, Noble D. The Millennium IGU: Regenerative concept for a 1000-year insulated glass unit. Glasscon Global Conference Proceedings, 2014, https://www.academia.edu/8534385/The_Millennium_IGU_Regenerative_Concept_for_a_1000_Year_Insulated_Glass_Unit.
⁴Princeton University Office of Capital Projects. Princeton University Facilities Department Design Standards Manual. Release 14.0, July 2022, https://facilities.princeton.edu/about-us/office-of-capital-projects.

Bill Millard is a New York-based journalist who has contributed to Architectural Record, The Architect’s Newspaper, Oculus, Architect, Annals of Emergency Medicine, OMA’s Content, and other publications.