Longevity and Sustainability of Curtain Walls

Will your facade last a few decades or a millennium?
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Sponsored by The Ornamental Metal Institute of New York
By William B. Millard, PhD

Learning Objectives:

  1. Apply your understanding of new efficiency properties for facade design with the goal of increasing curtain-wall longevity and reducing embodied carbon.
  2. Learn serviceability characteristics that can contribute to the life cycle of a curtain wall.
  3. Analyze the recyclability potential of constituent parts of a curtain wall.
  4. Balance resilience and sustainability attributes with properties promoting healthy interior environments for occupants to achieve the best performance and aesthetic goals.


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AAA 1 Structured Learning Hour
This course can be self-reported to the AANB, as per their CE Guidelines
AAPEI 1 Structured Learning Hour
MAA 1 Structured Learning Hour
This course can be self-reported to the NLAA.
This course can be self-reported to the NSAA
NWTAA 1 Structured Learning Hour
OAA 1 Learning Hour
SAA 1 Hour of Core Learning
This course can be self-reported to the AIBC, as per their CE Guidelines.
As an IACET Accredited Provider, BNP Media offers IACET CEUs for its learning events that comply with the ANSI/IACET Continuing Education and Training Standard.
This course is approved as a Structured Course
This course can be self-reported to the AANB, as per their CE Guidelines
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Approved for Core Learning
This course can be self-reported to the NLAA
Course may qualify for Learning Hours with NWTAA
Course eligible for OAA Learning Hours
This course is approved as a core course
This course can be self-reported for Learning Units to the Architectural Institute of British Columbia
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Photo: Ed Wonsek; courtesy of The Architectural Team

The Raffles Back Bay Hotel and Residences in Boston use a unitized curtain-wall system with an estimated lifespan of 60 to 70 years.

Designing a building with sustainability, resilience, and longevity in mind calls for a recognition of complexity and interdependence. Each component of a building contributes to its embodied and operational carbon footprint, its occupants’ experience, its architectural expression, and its economic performance. The building envelope is a particularly powerful determinant of these outcomes, since it comprises a large volume of materials, endures climatic and atmospheric stressors, and mediates between exterior and interior environments, transmitting or consuming widely varying amounts of energy in the process. The contemporary curtain wall, a product of over a century of technical evolution, can be one of a building’s vulnerable points, showing its age faster than the rest of the structure does. The converse of that observation is that improving a curtain wall’s quality and longevity is an opportunity to realize powerful gains in the whole building’s performance.

The 2024 Design Challenge sponsored by Metals in Construction magazine and the Ornamental Metal Institute of New York, eliciting proposals to design the curtain wall system of a new building at least 50 stories tall for a site on Broadway in midtown Manhattan, posits at least a 75-year anticipated service life for the proposed systems. This represents a substantial extension of the longevity commonly observed and expected in contemporary practice, say several experts in sustainable envelopes.

Mic Patterson, ambassador of innovation and collaboration at the Facade Tectonics Institute (FTI) and a member of the Design Challenge jury, cites a remark by Anthony Wood, executive director of the Council for Tall Buildings and Urban Habitat, at an FTI conference. “He said, ‘How long should a building last? It should last until we’re done with it,’ which I think is the right answer.... They should be modifiable, adaptable, and repairable as need be until we are completely done with them.” There is no one-size-fits-all criterion for a facade system’s durability, Patterson says. “It needs to be adaptable enough to accommodate changes in use and all of the forces of obsolescence.”

Patterson commonly encounters facade contractors’ expectations of 20 to 35 years for the life of a curtain-wall system, with 50 years as the customary upper limit, and he finds these figures unnecessarily low. “That ignores the synchronicity that needs to exist between the aspirations for the building itself and the facade system,” he continues. “If you’ve got a building that is designed to last 100 years and a facade system that’s still designed to last 75 years, you end up needing a new facade system before the building expires. And if you put a new one on there, that’s good for another 75 years, then you lose 50 years of facade-system service life. And so there’s all kinds of wasted durability going on in buildings and facade systems just because we don’t pay attention to that.” There is no reason, he believes, that certain buildings reflecting the most advanced realistic design and construction practices—coordinating components’ durability rather than leaving it to chance—cannot last a century, perhaps even 1,000 years.

In the U.S. curtain-wall industry, Patterson reports, it is common to market systems with a 35-year expectancy as “zero-maintenance systems to the building owners, which is what they want to hear. Basically, what we’re saying is, ‘This thing is good for 35 years, and then it’s done,’ because there’s no way to maintain it or retrofit it.” With few options for replacing or upgrading a facade system, “the only viable economic strategy in too many cases is to just rip the entire thing off and put a new one up”—the antithesis of sustainable practices, particularly when designs unwittingly create obstacles to the disassemblability, reuse, and recycling of materials.

The concept of zero maintenance, though attractive from a short-term perspective, appears roughly as realistic as a perpetual-motion machine. Patterson and other commentators contend that more farsighted approaches are within reach, however, for professionals who take a long-range view of the material cycles involved in design and product choices.


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Originally published in May 2024