Can an All-Glass Office Building Really Be Considered Green?

Looking up at glass skyscrapers in New York

Guido Cozzi / Getty Images

For decades, modern office buildings have been pretty much covered in glass curtain walls. Some are high performance and very expensive, like the super-green LEED Platinum Bank of America Building at 1 Bryant Park in New York, or they can be the standard crappy suburban office building thrown up across North America, looking the same in California or Calgary.

But as Steve Mouzon points out, even the very best glazing has an R-value that is equivalent to a 2x4 wall with fiberglass insulation, something that nobody has built for years. Most office buildings don't even approach a third of that. So why do architects design buildings this way?

Alex Wilson at Environmental Building News looks at the issue in Rethinking the All-Glass Building (subscription only). He writes:

Some of the world's most prominent "green" skyscrapers, including New York City's One Bryant Park (the LEED Platinum Bank of America skyscraper) and the New York Times Tower, wear the mantle of green with transparent façades. But there is a high environmental cost to all that glitter: increased energy consumption. Until new glazing technologies make technical solutions more affordable, many experts suggest that we should collectively end our infatuation with heavily glazed, all-glass buildings.

Alex summarizes some of the reasons that glass buildings are so popular, some of which I think are questionable, bordering on ludicrous.


Transparent skins provide access to daylight, and natural daylight is one of the leading drivers today of architectural design--green or otherwise.

But you can have too much of a good thing, and in most buildings the glass is tinted or mirrored to reduce the amount of daylight. At One Bryant Place, the glass is covered with a ceramic frit to reduce the daylight penetration; in the New York Times Building, it is covered with ceramic rods to reduce the amount of light. Any light below desktop height is pretty much wasted. So claiming that floor to ceiling glazing increases the amount of daylight is a bit specious, you can't possibly use that much of it. Ultimately, as Steve Mouzon notes, you don't need more than a third of the wall to be glazed to get all the light you could use.

Connection to the Outdoors

Closely related to daylighting is the visual connection to the outdoors that can be provided by a transparent façade.

Other architects might counter that you get a better connection to outdoors if you frame a view like a picture. Or that this only applies to the lucky employee sitting right next to the window; for everyone else that glass below the desk height is meaningless.

Transparent Corporate Culture

Many companies like the association of transparency with corporate image, as if it says, "See, we're in here, doing something for you; we're not hiding anything."

Really. So "transparent" gets picked up as corporate jargon and suddenly we are designing buildings around it? And with the tints and the blinds and the mirroring, can anyone actually see in?

Easier to Build

I think the reasons are simpler: laziness. In most cases, the architect is no longer really designing the exterior of a building, worrying about proportion and detailing and materiality, he or she is simply outsourcing the design to a curtainwall supplier. It looks really good on rendering, and makes it easier to get approvals; the simple, reflective skin disappears against the sky. It is easier to administer; one trade is providing the entire skin of the building. It's thinner; the client gets more rentable square feet.

So what if it is an energy hog, the tenant pays for that, not the owner.

Alex continues:

In general, heavily glazed buildings consume more energy than buildings with more moderate levels of glass. With a higher glazing fraction, solar heat gain, as well as heat loss in cold weather, are both greater. Glass does introduce daylighting, of course, and well-executed daylighting can reduce both electric lighting and mechanical cooling costs but the ideal percentage of glazing is far below that of many of today's prominent all-glass buildings.

Alex concludes by saying that "a growing body of experts in sustainable design argues that our architectural aesthetic should evolve away from all-glass façades."

But it will take a new breed of architects, who know something about commodity, firmness, and delight as well as the difference between a north and a south facade.

After I wrote favorably about the New York Times building two years ago, with its floor to ceiling glass, Green Architect disagreed with my admiration of the ceramic tube sun shading, with a comment that I will repeat here in full; his comment seems more appropriate than ever, and my response now seems particularly stupid.

You've fallen for the "Hybrid-SUV" trap, Mr. Alter.
The ceramic sun shade isn't solving an unavoidable environmental problem. It is mitigating the problem caused by the overuse of glass.
Like the SUV, "transparent" buildings have become a cultural icon. In both instances there are techniques that can lessen their environmental impact, but clear-minded individuals ought not be lulled away from questioning the necessity of the underlying practice.
Every "benefit" of the sun shade (reduced solar gain, internal reflectance, ect.) could be achieved much more effectively by properly proportioned glazing and a light-shelf, and use materials representing drastically less embodied energy.
A poorly designed building that employs mitigating features is not "green". As a green architect, I expected better out of a Treehugger contributor.
LA: Your point is well taken. Here I took the Times at their word that they thought about it:
"The New York Times selected a design that codified its philosophy of a "transparent" organization and one dedicated to creating a high quality work environment for their employees. The exterior of the building was proposed as a transparent floor-to-ceiling, all-glass façade that encouraged openness and communication with the external world. For a corporation whose daily business is gathering and disseminating news, facile communication between departments was encouraged by a number of the design features selected."