Avian-friendly glass: A clear and present solution for birds

by nithya_caleb | April 18, 2020 12:00 am

by Jen Miret

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Significant change is coming to new construction projects in New York City. Last December, the city lawmakers adopted legislation[2] requiring bird-friendly glass on new construction and all major renovations. The goal is to reduce the number of bird fatalities from accidental collisions with the transparent building skins.

New York City is not alone. Several others have already established bird-friendly construction standards. The San Francisco Board of Supervisors approved the Standards for Bird-safe Buildings[3] in 2011. Oakland followed just two years later, and since then more California municipalities have adopted bird-friendly requirements[4]. Initiatives are now under way in Chicago and Washington, D.C. The American Bird Conservancy (ABC), the pre-eminent authority on bird-friendly architecture, is also advocating a bill to enact nationwide bird-friendly guidelines for federal buildings.

Defining bird-friendly glass

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Birds see the world differently from humans. A beautiful glass structure or a window, to birds simply seems like an unobstructed opening they can fly through. They perceive glass reflections as open skies, trees, or gardens, which are normally safe areas to fly toward at full speed.

In this case, however, they are not—and the results are usually deadly. Accidental bird strikes are jarring for building occupants and disastrous for the birds themselves. The solution is architectural glass designed specifically to work with avian eyesight, making it more readily recognizable as a solid obstacle.

The stakes

“Every year, over two billion birds die from window collisions in this country,” said Rafael Espinal, New York council member. “Since New York City is along the bird migration route, between 90,000 and 230,000 birds, from hawks to hummingbirds, die from flying into buildings in our city. This is a staggering statistic especially when we have a solution ready to go that can save the many lives of this vital part of our ecosystem.”

The challenge for glass companies is to develop attractive, affordable, and effective bird-friendly glass products. In 2016, ABC identified a proprietary channel glass from a New York City-based manufacturer as bird-friendly, making it the first 3D (U-shaped/channel) glass to receive Bird-smart certification[6] (Figure 1).

For the certification process, the manufacturing company submitted its glass for testing at the Pennsylvania Powdermill Nature Reserve flight tunnel, one of only three such facilities in the world. The bird-safety ratings derived from this type of tests have become the basis for the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) Pilot Credit 55 “Bird Collision Deterrence,” as well as bird-friendly design ordinances nationwide. An increasing number of bird-friendly glass products are now available, and the demand is growing.

“Everyone has seen or heard a bird hit a window, but few realize how common it is—adding up to hundreds of millions of birds each year in the U.S. alone,” said Christine Sheppard, the bird collisions campaign manager for ABC.

A sight unseen

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Birds perish simply because they are unable to see glass on their flight path. According to ABC[8], “because of their small size and high-speed flight, birds hit glass and are usually killed or sustain injuries that will likely kill them.” More than 258 species, everything from hummingbirds to falcons, are documented victims of collision.

Glass reflecting skies or vegetation attracts birds, leading to collisions. Green habitats inside buildings with see-through façades, which is a growing trend, can also lure birds to their deaths. Glass corners or narrow glazed passages are other risk factors. Building strikes are second only to domestic cats as the most dangerous direct threat for avians.

Birds are also threatened by their migration patterns. Many travel along the densely populated ‘Atlantic Flyway,’ which hugs the U.S. eastern seaboard. “Located at the nexus of several migratory routes, New York City’s tall buildings with reflective glass pose a serious threat to over 100 species of migratory birds, some of which are experiencing long-term population declines,” according to the New York City Audubon Society[9]. Chicago, which is located along the ‘Mississippi Flyway,’ is the most dangerous city[10] in the United States for migratory birds. The Chicago Bird Collision Monitors (CBCM) recover about 6000 birds in a 4-km² (1.5-mi²) area each year.

Game-changing glass

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Bird-friendly architectural glass has been available for many decades, even though it has not always been marketed as such. This glass is visible to birds as it has bird-safe decorative pattern or a surface texture that breaks up continuous reflections.

The rule for these bird-safe patterns is based on research and testing. It is clear and simple, and also allows design professionals and glass manufacturers tremendous creative freedom. Known as the ‘2×4 rule[12],’ it stipulates glass patterns should be spaced no more than 50 mm (2 in.) apart vertically, or 100 mm (4 in.) apart horizontally (Figure 2). This is based on the findings that birds will not attempt to fly through openings that are less than 50 mm high or 100 mm wide. This means a wide range of designs, from timeless linear patterns to stylized nature-inspired motifs, can be employed in bird-safe glass architecture. Applied through a range of contemporary decorative glass technologies, including fritting, printing, etching, and carving, they can add originality and character to the building.

When creating bird-friendly glass designs, following the 2×4 rule is the best place to start. ABC also offers flight tunnel testing for bird-smart glass products. Spaces are limited and testing is performed in the spring and fall time only, making it best suited for standardized glass products with wider market appeal.

Bird safety testing

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ABC’s bird safety glass testing[14] takes place at the Powdermill Nature Reserve in Pennsylvania. Avian researchers at the facility use fine, flexible nets to gather hundreds of birds during their spring and fall migrations. The researchers examine and band each bird. Then, they release them into a special test tunnel—one of only a few in the world. Each bird is tested once only, and no birds are harmed during testing.

Inside the tunnel, the bird is presented two glass options to fly toward: a plain, clear glass control sample and the test glass sample. The goal is to see whether the bird would avoid the test glass. A delicate flexible net at the end of the tunnel gently captures the bird, and prevents it from striking the glass. It is then safely released. Each flight path is digitally recorded and examined by the researchers. The results can determine whether the test glass is an effective bird-friendly material, worthy of ABC’s Bird-smart certificate.

Bird-friendly glass types

The following are some of the most effective bird-friendly glass solutions.

 Textured glass

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One of the most effective bird-friendly solutions is glass featuring a surface texture that breaks up continuous reflections. Most of this glass is produced by the ‘rolled pattern’ process, where a ribbon of semi-molten glass is pulled through a set of steel rollers. Designs engraved on one or more of the rollers transfer onto the glass surface. The ‘imprinted’ glass ribbon is then slowly cooled, cut into sheets, and tempered and/or laminated for exterior applications.

This type of bird-friendly glass tends to perform well throughout the day and night. It is available in a large variety of regular and low-iron (ultra-colorless) glass designs. It is also one of the most cost-effective ways to add a decorative element to a building. As an added benefit, textured glass is an outstanding diffuser of light, often eliminating the need for secondary daylight control devices and creating an attractive soft glow at night.

Among its limitations are the relatively small sheet sizes (ranging anywhere from around 1270 x 2032 mm [50 x 80 in.] to 1270 x 3302 mm [130 in.]), the difficulty and expense of custom patterns, and a greater degree of view obscuration. Several of these concerns can be addressed by choosing a more specialized type of textured glass, such as channel glass.

Channel glass

Channel glass is a 3D, self-supporting glass that can reach heights up to 7 m (23 ft). Hundreds of channels can be lined up to create expansive glass walls free of interim metal framing. It is typically specified in one of several light-diffusing surface textures, and is also available in a relatively ‘clear’ form used as vision lites. The collision avoidance performance of ‘clear’ channel glass was a concern, and the glass was tested at the Powdermill Nature Reserve flight tunnel. In testing, it proved to be an effective deterrent and earned the ABC Bird-smart certification[16]. The rhythmic vertical seams of the abutting glass channels likely contributed to this see-though material performing as a bird-friendly glass product.

Recent channel glass projects in major cities along migratory bird routes include New York City’s South Street Seaport, Pier 17, and Capital One Bank’s Chicago flagship. At Pier 17, approximately 4088 m² (44,000 sf) of ‘rough cast’ textured channel glass create a 12-m (40-ft) tall, light-diffusing rainscreen façade, designed by SHoP Architects & R.A. Heintges and Associates. At Capital One Bank by IA Interior Architects, alternating clear and textured glass channels offer selective privacy, while maintaining visibility to the street.

Spandrel glass

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Full-coverage fritted glass, also known as spandrel glass, is non-see-through and is an effective bird collision deterrent. Available in hundreds of colors, it can conceal the building’s structural elements, while enhancing its design. It is manufactured by applying a thin layer of colored frit to the glass surface. The frit is essentially colored glass in the form of fine pulverized powder. Heating it in a tempering furnace to approximately 650 C (1200 F) melts and permanently fuses the color. It also transforms the glass into tempered safety material, meeting the requirements for ANSI Z97.1, For Safety Glazing Materials Used In Buildings – Safety Performance Specifications And Methods Of Test, and the Consumer Product Safety Commission (CPSC) standard 16 Code of Federal Regulations (CFR) 1201, Safety Standard For Architectural Glazing Materials.

New York City’s Liberty Park at the World Trade Center features white fritted glass in a decorative ventilated façade. The structure was designed by AECOM to dress up a vent for a below-ground parking garage.

Pattern-fritted glass

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Available in multiple colors and virtually unlimited custom designs, pattern-fritted glass using the 2×4 rule is a bird collision deterrent. Among the chief benefits of this type of bird-friendly glass is the creative freedom it offers, as well as its large panel sizes, which are ideal for contemporary, expansive façade applications. A key aesthetic benefit is it can appear perfectly clear when viewed from afar, while still effectively preventing bird strikes.

Pattern-fritted glass is produced in the same way as full-coverage (spandrel) glass, with the addition of one critical step—a stenciled screen is applied in order to create the specified glass design. This technique is known as screen printing.

This technique was used to create the custom, hawk-wing inspired façade for the University of Iowa Kinnick Stadium expansion, designed by Neumann Monson Architects. The glass panels reach over 1524 x 3810 mm (60 x 150 in.) in size. They feature a variety of custom linear designs and sizes, as well as several custom shapes, to convey the architects’ vision. Extra-large print screens were produced to create the custom fritted design. Each glass panel was then carefully aligned to one of the screens to generate the mixed imprints. Thus, a diversity of patterns was made for the 1301 m² (14,000 sf) of glass needed, minimizing costs by using just three screens.

Surface #1 fritted glass

At Johnson County Community College by BNIM, surface #1 pattern-fritted glass creates a white ventilated façade, filtering daylight into art studios and classrooms. The specified glass is a combination of a dot-pattern frit on the outside, laminated to full-coverage, light-diffusing etch on surface #4 (facing the interior of the building). The use of ultra-clear, low-iron glass and white frit on the outermost surface creates the exceptionally bright white aesthetic.

Surface #1 frit patterns designed to the 2×4 rule are among the most effective bird collision deterrents known to date. Placing the print on the outermost surface of the glass breaks up continuous reflections, making the pattern easily visible from various angles and under different light conditions. As an added benefit, façades such as this can also be used for projection, instantly transforming the building into a gigantic art display.

Digitally printed glass

Non-repetitive designs for bird-friendly glass applications can also be produced using a direct-to-glass printing technique. It uses pigments similar to the frits used in screen printing, but each color is applied to the glass akin to a desktop printer, adding the ability to create multi-colored designs and photo-realistic glass murals. Once the design is imprinted onto the glass, it is tempered to set the colors.

Unlike screen printing, which can be applied to any of the glass surfaces, direct-to-glass imprints are recommended on the #2 or #3 surface of the glass, away from direct exposure to the elements. They are usually protected by another piece of glass added through lamination or an insulated glass unit (IGU). Lamination is the process of permanently bonding two or more glass lites with a flexible or structural (rigid) interlayer, under the combined forces of heat and pressure. The interlayer prevents the pass-through of objects in the event of glass breakage and makes the glass safe, meeting the requirements for ANSI Z97.1 and 16 CFR 1201. Structural interlayers also add strength to the glass, allowing it to span greater heights under the imposed wind loads.

Another method to achieve the same or similar aesthetic is imprinting an interlayer and laminating it between two lites of clear glass.

Among the few limitations of digitally printed bird-friendly glass is its higher cost and slower fabrication, due to the time it takes to imprint each glass lite. However, it is the most appropriate solution for façades featuring varied designs.

Other types of bird-friendly glass

Etched glass is one of the most reliable and time-tested ways to make a glass façade bird-friendly and aesthetically pleasing at the same time. Similar to fritted glass, etched glass can be full-coverage or patterned, and is most effective when the etching appears on the #1 (outermost) surface of the glass. It is produced by exposing the glass to hydrofluoric acid, creating its characteristic frosted appearance and satin-smooth, maintenance-friendly finish. Sustainably produced acid-etched glass incorporates recycling the acid, and then neutralizing it for safe disposal.

Architects and designers can select from a wide variety of existing patterns and designs conforming to the bird-smart 2×4 rule, or design their own. Custom etched patterns can be costlier than custom printed and custom fritted designs, due to the price of the screens and minimum order requirements.

Another method to create the frosted aesthetic is sandblasting, which is bombarding the surface of the glass with sand or other particles. The disadvantage of this technique is a slightly rougher glass surface that is more prone to trapping dirt. The more maintenance-friendly method to create simulated etched glass is through fritting, using a translucent frit that mimics the frosted look.

Ultraviolet (UV)-pattern glass is among the newest method to apply patterns to the material, and was developed specifically for bird-friendly glass applications. A UV-reflective coating is used to create 2×4 bird-safe patterns, which are mostly invisible to humans, but easily perceived by those bird species able to see light in the UV spectrum. UV-pattern glass is currently available from a single provider, and its manufacturing process is proprietary. The chief limitation of this type of bird-friendly glass is its cost.

Cost of bird-friendly glass

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The cost of bird-friendly glass varies significantly based on the project size and glass type. It is best to consult the glass façade supplier for the most efficient way to produce the desired design. For example, screen-fritted glass is cost effective for repetitive patterns, while digitally printed glass is best suited for non-repetitive designs. The size of the project is the key pricing factor. Replacing a few lites of clear glass with a bird-friendly one may not have a tremendous effect on the overall budget, but will likely mean a substantial price differential between the two materials. On large-scale projects, a bird-friendly pattern may have a relatively small effect on the overall budget. For example, the addition of custom frit design on Kinnick Stadium contributed approximately five percent to the cost of the façade, while having an outsized role in the aesthetic, solar shading, and the bird-friendly performance of the envelope.

 Why more buildings are not bird-friendly

A mix of relatively low public awareness, insufficient knowledge of the variety of cost-effective solutions available to the architects, designers, and developers, as well as aesthetic preferences for ultra-clear glass have stood in the way of more bird-friendly architecture.

Focused educational and advocacy efforts by wildlife conservationists, USGBC, and eco-minded building professionals are poised to tip the scales. Additionally, for well-educated end-users, the many benefits of bird-friendly design often outweigh the preference for perfectly clear glass.

From a design perspective, all the discussions on bird-smart glass could benefit from reframing the issue—from one where clarity and unobstructed views are ‘sacrificed’ to one where elegant bird-safe design becomes an opportunity to:
● impart a unique identity to a building;
● offer building occupants better visual privacy;
● bring in higher quality, filtered daylight to interiors; and
● achieve gently veiled, mostly unobstructed views.

 Trends in design

Over the past few decades, more buildings have been constructed with all-glass walls and there has been an increase in the amount of glass in construction. Transparent glass façades, balconies, railings, and larger glazed openings add architectural appeal, but also increase the risk of bird collisions.

Architects are beginning to discover the benefits of bird-friendly glass as well. In 2009, the Jacob K. Javits Convention Center in New York City had one of the highest bird-collision mortality rates in the nation. During a major renovation and expansion in 2014, the architectural firm FXfowle replaced the reflective glass with opaque panels at the street level, and installed large panes of pattern-fritted glass[20] throughout the rest of the façade. The project also included a new 3-ha (7-acre) green roof to serve as a bird habitat. After the renovations, bird collisions fell by 90 percent.

Retroactively, on the myriad of tall buildings already built that have clear glass façades, one could apply a bird-friendly filter that meets the 2×4 rule. Sporadic bird-of-prey decals, however, are not recommended as they do not work.

New legislation will go a long way toward helping reduce the number of bird collisions. Sheppard from ABC sees the law as an important step in demonstrating bird-friendly design can, and should, be implemented.

“Bird-friendly building design should not be seen as an add-on or extra,” Sheppard said[21]. “Many strategies for controlling heat, light, and even security can be bird-friendly strategies, too. These can be incorporated into almost any building style, but should be built into project design from the outset to minimize additional costs. That is why this kind of legislation is so important.”

[22]Jen Miret is the director of marketing for Bendheim. She oversees the business’ development of continuing education programs for architects, designers, and building professionals. She can be reached at jmiret@bendheim.com[23].

Source URL: https://www.constructionspecifier.com/avian-friendly-glass-a-clear-and-present-solution-for-birds/

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