What a Glass City Can Do With Its Sunlight

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What a Glass City Can Do With Its Sunlight

In an age when glass buildings are common and energy efficiency is a top priority, it may be time to take a new look at the management of sunlight in cities.

Manhattan’s Chinatown. Credit: Karen Loew

The light show that takes place each day in densely built cities is an accident, hardly considered by architects, designers or everyday observers. Modern cities filled with glass scatter patterns and shards of light — that’s just what they do. This benign phenomenon, which I call “glimmerance,” has never made headlines.

But its blinding cousin, the media-dubbed “death ray,” recently became news. In Dallas, the Museum Tower generated a reflection bright enough to endanger artworks and damage the landscaping at the adjacent Nasher Sculpture Center. In London, a skyscraper at 20 Fenchurch Street, nicknamed the “Walkie Talkie” and still under construction, focused light intensely enough to singe a doormat and melt moldings on a car.

In an age when glass buildings are common and energy efficiency is a top priority, it may be time to take a new look at the management of sunlight in cities. In mid-Manhattan alone, new forests of glass towers have been proposed for both Hudson Yards and East Midtown. Eventually, cities that keep putting up so many of these buildings will run into some questions. Are glass towers reflecting too much light or heat? Do they generate a larger carbon footprint because of less insulation? Are there new answers to the old problem of living in the shadow of a high-rise, and new ways to aesthetically shape light and shade?

Excessive light or heat “has never really been broached as a political or public policy issue,” said architect Davidson Norris of the Manhattan firm Carpenter Norris Consulting. “There really needs to be some sort of dialogue established about the density of building in New York City and its impact, one, on its reflected heat, and two, because of shading.”

Policy responses to excessive shading alone have been on the books since New York’s Zoning Resolution of 1916, inspired largely by the just-built 42-story Equitable Building and its seven-acre shadow. This first comprehensive set of land use laws in the nation dictated rules about heights and setbacks intended to ensure adequate light and air for all.

In the LEED era, city leaders expect building materials to be energy efficient. Norris and other architects wonder whether the kinds of glass and glazing used today, designed to let in precisely the amount of light and heat desired, have simply deflected environmental issues from private interiors to the public sphere.

Russell Unger, executive director of the Urban Green Council, doesn’t think ubiquitous glass walls are fanning the flames of the urban heat island. “I haven’t heard complaints about localized heating from a building, apart from these unusual news reports, where you have the building concentrating wavelengths in one small area,” he said.

Unger called the 20 Fenchurch death rays “pretty much a freak accident.” His environmental critique faults glass buildings for a different reason: Their relative weakness, compared to stone or masonry, as insulation.

Astor Place in Manhatan. Credit: Karen Loew

“The best window in the world is a terrible wall,” he said. “What a window does for insulation is far less than a wall can do.” He would like to see buildings use enough glass to let in plenty of light — between 40 and 50 percent of wall surface area — rather than the 70 to 80 percent sometimes built now.

Demand drives building styles, and real estate people have told Unger that gigantic windows (or lots of “vision glass,” as compared to the “spandrel glass” panels that run between floors) are perhaps the number-one selling point for apartments. Yet research, he said, shows that in typical high-rises with lots of vision glass, the shades are pulled down.

“What is driving this trend?” he asked. “Is it really the tenant saying, I want this high-glass experience?” People may actually want less noise and more privacy.

At Guardian Industries, the Michigan-based company that manufactures glass for such edifices as World Trade Center I and Dubai’s Burj Khalifa, the world’s tallest building, the message is still the more glass, the better. The company touts its white paper, “The Benefits of Glass,” as well as its newest product, SNX 62/27, which lets in 62 percent of sunlight and 27 percent of solar heat.

“You can make a tremendously energy-efficient building with glass, and we would disagree with the notion that a blanket reduction [in glass use] makes sense, or is what people want,” said Chris Dolan, director of commercial glass products at Guardian. He also rejected the idea that highly reflective glass overheats its surroundings, echoing Unger in calling the Walkie Talkie’s scorching properties “highly unusual” when so many buildings in the world are covered in glass and incident-free. (Guardian wasn’t involved in that building, and architect Rafael Vinoly, who has previously blamed consultants, declined an interview.)

Astor Place in Manhattan. Credit: Karen Loew

In any case, death rays coming from mirrored buildings may become even more rare. “The general trend that we see in the market is higher light transmission and less reflection,” Dolan said. New buildings don’t necessarily look like mirrors, but have enough reflectivity to provide some privacy. Another trend is growing interest from architects in silk-screening or digital printing images onto sheets of glass. For a major new building at Concordia University in Montreal, Guardian provided glass panels printed with colored images of leaves, creating a striking wall mural. (See third image here.)

Sunlight coming through such window murals might have interesting effects inside. Conscious engagement with natural phenomena is a choice some would like to see embraced more often. Architect Linda Pollak, who also studied landscape architecture, is interested in reflections and shadows. “A lot of architecture is focused on the building as a whole,” she said. “The building is kind of like an object. Its impact is understood at that level. But how it interacts with the environment happens at a lot of different scales.”

Reflections are something that designers of all kinds “could pay more attention to,” Pollack said. Although architecture tends to concern itself with permanence, elements like texture and time “could add up to something that’s really primary.”

Norris isn’t leaving it to chance. A leader in the use of heliostats, or large reflecting mirrors that shine light from rooftops down to a shady patch of ground — as in Manhattan’s Teardrop Park — he is busy developing a tool for harnessing reflections. He’s working with caustics, or light with darker and brighter areas caused by a reflective layer that isn’t absolutely flat (think of the patterns in a swimming pool).

“We are working with a team of researchers who have come up with a way to take a reflected caustic — which is essentially a random image as we’ve known it so far — and they’re able to develop caustic surfaces that can project a very coherent image,” Norris said. “It ends up being not so much image-making with light, but actually drawing with light, and then you’re able to draw with light at an urban scale or an architectural scale.”

He envisions unveiling Hokusai’s The Great Wave off Kanagawa on the side of a building soon, in what he gamely referred to as “targeted glimmerance.” Until then, and long afterward, glimmerance will continue.

Tags: real estatebuilt environmentarchitecture

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