Bird-safe glass: codes and standards to know

by arslan_ahmed | December 16, 2022 9:00 am

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By Julia Schimmelpenningh 

Thanks to the pioneering work of dedicated scientists, ornithologists, wildlife associations, and the glass industry, the future is looking brighter for the billions of birds which end up colliding with windows each year. While still in its infancy, the science of bird-safe glazing is emerging with creative new ideas and changing the way birds see and react to building glass. Similar to the evolution in hurricane-resistant glazing, which began several decades ago, the road to developing adequate bird-friendly codes, local ordinances, and glass testing is evolving. For specifiers tasked with selecting bird-friendly glazing, this article provides an overview of current glass testing options and other information to help when designing a beautiful yet bird-friendly building.

How big is the problem?

Birds are essential to the ecosystem. They consume vast quantities of insects and control rodent populations, further reducing damage to crops and forests and limiting the transmission of diseases such as the West Nile virus, dengue fever, and malaria. Birds also regenerate habitats by pollinating plants and dispersing seeds.

With the increase in glass as a design medium, bird collisions into architectural fixtures and buildings have also increased, and awareness of this has become a chief driver for bird-friendly guidelines and regulations. Technical improvements and performance capabilities have made glass more accessible and desirable for architects; however, its transmissive and reflective nature, although beautiful to humans, can confuse birds.
Birds cannot distinguish the presence of glass in architecture, so they attempt to fly through it. If the glass is reflective, it can present an oasis effect by somewhat mirroring the surrounding vegetation and environment, drawing birds into a reflection of the world around them which is not real.

Glass on lower levels, closest to the ground, and adjacent to “green” patios and balconies can reflect vegetation or landscapes, posing just as much risk for bird strikes as upper-level glass reflecting clear skies or providing seemingly pass-through corridors for flying. Birds attempt to reach habitats, open spaces, or other attractive features visible through or on glass surfaces.

Birds use their eyesight to orient themselves, but most birds have eyes on the sides of their heads. This allows them to see sideways at a wide angle, giving them a view of any approaching enemies or mates from all directions. The disadvantage, however, is their spatial vision is severely limited, and they have difficulty recognizing obstacles in fast flight. Birds in flight may only see the landscape behind the pane of glass and fly against it unchecked.

Beyond tall buildings

While the blame for bird collisions is often concentrated on tall buildings, skyscrapers are only part of the equation. According to a report on glass collisions, “Most collisions take place during the day, and almost half occur at home windows; low-rise buildings account for almost all the rest.”¹

Tall buildings, buildings with green balconies and rooftops, and wide buildings with large expanses of glass also cause enough bird collisions to make bird-friendly glazing a priority for all levels of architecture, from suburban homes to urban skyscrapers.

Dangerous migration flyways

Bird migration patterns occur worldwide, with eight major migratory pathways through the Pacific Americas, Central Americas, Atlantic Americas, East Atlantic, Black Sea-Mediterranean, East Asia-East Africa, Central Asia, and East Asia-Australia. However, even without these migratory paths, birds residing in the same location all year are just as much at risk of glass collisions.

Typically, birds’ encounters with glass are fatal, as they have weak skeletal systems and the impact at full flight can be crushing. Birds tend to collide with glass at high speeds and their small bodies, composed of hollow bones, leave them vulnerable to injury or usually, a fatality.  Healthy and mature birds are just as likely to collide with windows as young, vulnerable ones.

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Bird testing facilities

With the adoption of bird-friendly glazing in its infancy, testing and experiment facilities are also evolving. Although interest in developing more test sites is growing, manufacturers in North America currently only have limited options to test their products. Since live birds are used in the process, the process is highly specialized and requires specially trained experts to conduct testing while ensuring bird safety. To meet new building requirements for sustainability and eco-friendly products, manufacturers have teamed up with ornithologists, who study and understand how birds live and adapt to their surroundings.

Canada uses a different, prescriptive approach for bird safety. The CSA Group (CSA) created the standard, A460:19, Bird-friendly building design, to establish best practices for industry professionals and government agencies to use to deter bird collisions. This standard covers bird-friendly building designs in new construction and existing buildings and is intended to reduce bird collisions with buildings. It also provides design requirements for glazing, building-integrated structures, and overall building and site design. As it is a prescriptive document, it is based on knowledge and testing available at the time of writing. With the rapid evolution of techniques to create highly effective glazing products, the standard is subject to change.

In the U.S., the American Bird Conservancy (ABC) has two tunnel test sites. The Powdermill Avian Research Center (PARC) in Rector, Pennsylvania, is part of the Carnegie Museum and is located on the 891-ha (2200-acre), Powdermill Nature Reserve. Earlier this year, the ABC joined forces with Washington College in Chestertown, Maryland, to double its capacity to test and rate glass and other materials and their ability to deter bird collisions.² The move is already helping in meeting the high demand for testing from glass manufacturers, while allowing the science and knowledge around bird-friendly glazing to develop and evolve. ABC also collaborates with its European counterpart, Biologische Station Hohenau-Ringelsdorf in Austria.

A third U.S.-based option for testing is at the Acopian Center for Ornithology at Muhlenberg College in Allentown, Pennsylvania. Field testing, which is a different methodology than tunnel testing, is conducted here. The Center also provides hands-on training in natural science through specialized classes and collection-based research opportunities for the college’s biology students.

Also in the U.S., the National Glass Association (NGA) has developed a “Best Practices for Bird-Friendly Glazing Design Guide,” which offers prescriptive recommendations to implement bird-friendly glazing constructions. The document reflects the current developments and guidance available within the glazing and bird conservancy industries. The design guide is also noted as a point of reference for all architectural projects.³

 How testing works

Currently the two broadly accepted approaches are tunnel and field testing. While each has its advantages and disadvantages, both methods are used to advance the quality and efficacy of bird-friendly glazing systems.

Tunnel testing

In 2004, the Biologische Station Hohenau-Ringelsdorf debuted an outdoor protocol to compare effectiveness of different patterns on glass for preventing bird collisions. The Hohenau-Ringelsdorf tunnel is a binomial choice protocol. Birds, protected by a net, have the option to “exit” the tunnel by flying either towards a test sample or unmarked control glass, seen at the far end of a dark, enclosed space. The tunnel was constructed (and is still operating) at Hohenau, a bird banding station, where netting migratory birds makes it possible to test large numbers of samples in a relatively short period.

The ABC adopted a similar protocol; PARC is a permanent banding station led by scientist, Dr. Christine Shepard. In a typical year, more than 11,000 birds of 100 species are netted, banded, measured, visually sexed, and weighed. Most are migratory birds netted during spring and fall migrations. In a relatively short period, this provides large sample sizes of species which are typically victims of collisions.

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The PARC tunnel is 8 m (27 ft) long with a cross section of 1 x 1 m (3.3 x 3.3 ft) at the sample end, tapering to 0.45 x 0.45 m (1.5 x 1.5 ft). The tunnel is open at the sample end. A mounting apparatus holds two 1 x 0.5 m (3.3 x 1.65 ft) panels separated by a 100-mm (4-in.), 6-mm (0.24 in.) clear window glass control (supplemental materials A) and a test sample. A net prevents birds from hitting the glass. At the operator end, a lightproof sleeve permits birds to be released in a dark interior, with brightly lit “exits” viewed at the far end. A video camera is mounted to record flights, and control glass permits direct comparison of samples in the same trial.

The tunnel is mounted on a pivot and is moved every one to five minutes to keep a constant orientation, with the sun directly behind the operator. Timing depends on visual assessment of shadows before each trial. Mirrors at the sides of the tunnel reflect light onto the front surfaces of the glass, and natural light falls on the back surface. Test materials are presented in a random order and in equal frequency on the left and right sides.
At the start of the testing season, trials using two clear panes are run as a control. Equal numbers of flights to the sides indicate the tunnel itself is not influencing the choice made by the birds. A tunnel score of 50 (±5) means a test glass product does not influence flight direction.

The ABC focuses on how many times birds approach the glass samples in the tunnels. Following testing, ABC provides manufacturers with a bird-friendly rating, called a threat factor. Developed in 2010, a threat factor is a way to assign scores measuring a bird’s ability to see and avoid patterned glass and other materials. This rating makes it easier for direct product comparisons but also allows governments to enact bird-friendly policies and architects to design bird-safe structures.

Unlike a traditional test lab, ABC typically only tests products which advance the science in some new way. Based on past research, there are certain parameters which are effective. Leading researchers on the topic have already identified the required spacing, length, width, opacity, colour, and orientation of elements marked on glass. These determined parameters become the basis of prescriptive or permitted products and substitutions.

The key benefit to tunnel testing is it produces rapid reproducible results. Tests can be usually completed in a day. The two North American testing facilities can issue a threat factor, and based on the score, architects design buildings using rated glass. The test also permits the evaluation of products which can be applied to existing glass (retrofits) to reduce collisions.⁴

A lower threat factor score means the product is more effective at reducing collisions. Glazing product manufacturers strive for a threat factor of 30 or under.

Field testing—a natural option

Field testing is offered at the Acopian Center for Ornithology. In field tests, the setup simulates how a window will behave when installed in a “human” structure. The windows in the field experiments look (to both birds and humans) exactly as they would if installed on a building—as a see-through, reflective window. Similar to actual buildings, the reflective windows cover a recessed dark interior. This is done because a perfectly clear pane will act like a mirror, reflecting the facing habitat and sky if it covers a dark interior. Most window installations in the built environment result in reflective panes.

This field testing examines the effectiveness of systems by using birds in their natural settings, where they live and move about. Birds are monitored while interacting with systems as they would at any human structure they are attracted to or encounter in their daily movements. Field testing depends on the chance of free-flying birds having a glass panel in their flight path. Feeders are used to increase the odds of the birds flying towards the glass.

Field testing is representative of the conditions during the exposure period and does not assign a threat factor to the rating. However, for manufacturers who want to take advantage of the real-world results of a field test, this may be an option to consider.

Bird-friendly glazing design parameters

Some well utilized and substantiated patterns have been derived from years of testing.  For example, certain maximum distances (e.g. 100 mm [4 in.] for vertical stripes, 80 mm [3.25 in.] for dotted grids and for horizontal lines, 50 mm [2 in.]) have proven to be effective in preventing collisions. Patterns covering as little as one to five per cent of the total glass surface can deter most strikes under experimental conditions. As a rule, most birds will not attempt to fly through horizontal spaces less than 50 mm (2 in.) high or through vertical spaces 100 mm (4 in.) wide or less. This has become known as the “2 x 4” rule, and it relates to the size and shape of birds in flight.

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Given a choice between translucent or white stripes, white stripes perform better because light is more visible against the background reflections. The stripes should be at least 3 mm (0.125 in.) wide. While humans see patterns, birds focus on the spaces within patterns. Dot patterns have been found to work well using the traditional 2 x 4 rule if the dot diameter is at least 6 mm (0.25 in.) in size. Generally, products meeting this criteria do not need to be tested.

Coated glasses can be utilized with many of these materials; however, the key parameter is ensuring the visible light reflection (VLR) is low enough not to further confuse the bird in flight.  The ABC typically sets an upper limit on VLR at 15 per cent, although, based on recent test results, some products may use coatings with a VLR of up to 19 per cent. The visual marker should be located as close to the external surface as possible, in some cases, for effectiveness, the technology may need to be put on surface 1, however, the markers are typically placed in front of the coating.

There are other technologies which utilize ultraviolet (UV) inks or coatings, three dimensional sequins, first surface etch or appliques. All the technologies are subject to the same guidelines on spacing with the goal to ensure a bird “sees” the visual noise and changes its path to fly away from the glazing.

Consideration of the technology may impact the decision of where to place the coating, for example, surface 2 with a frit on surface 1, or surface 4 or 5 of a laminated insulating glass may be the proper configuration for a project. Each project needs to be assessed based on the needs of safety, structural, security, energy, and bird-friendliness.

Canadian prescriptive guidelines

Canada uses a standard or set of guidelines different from the U.S., which allows both prescriptive and actual tests results to be considered for inclusion on a project. Key elements of these tests are:

• Visual markers should be used in a glazing unit
  (first surface) to address both see-through and reflective conditions.
• Spacing of visual markers should meet the “2 x 4” rule.
• Visual markers should meet a minimum size of 3 to 4 mm (0.119 to 0.159 in.), depending on the geometry.
• Visual markers should be in high contrast to the glazing material.
• Visual markers should be used in high-risk collision zones—the first 12 to 15 m (40 to 50 ft) from grade, corners, and floors adjacent to green roofs.
• Visual markers should be considered for glazing on building elevations, balcony railings, ramps, and free-standing glass structures.

The standard, CSA A460:19 was written in 2019, and has not been updated since. For manufacturers with emerging technologies, including products which are not placed on the first surface, certain locations in Canada may be a limited market opportunity and may require special review and approval of test results before permitting the use of a bird-friendly glazing. Although CSA A460:19 is a guideline and written in prescriptive language, emerging technologies with appropriate tests reports are being considered and utilized throughout North America.

Legislation and LEED

The United States Green Building Council (USGBC), which issues the Leadership in Energy and Environmental Design (LEED) certification, points, and credits when buildings achieve specific standards in several sustainable building categories, has also been influential in creating bird-friendly glass and glazing solutions. In 2011, USGBC added Pilot Credit 55 titled “bird collision deterrence” to its library. A revised version of the credit in 2015 expanded its availability to all LEED rating systems except neighbourhoods. The credit contributes to LEED points with Pilot Credit SSpc55 in Core and Shell. The Green Building Initiative, Green Globes’s New Construction 2021 Technical Reference Manual, also includes the opportunity for points in its rating system related to measures addressing bird strikes.

In the U.S., H.R. 1986—the Federal Bird Safe Buildings Act of 2021—has been introduced in Congress. If passed, the act will ensure that all U.S. government buildings, regardless of location, are built bird-friendly. In the meantime, many large North American cities, including Toronto, New York, San Francisco, and Chicago have passed strict local guidelines as well.

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Conclusion

Reducing bird mortality from glass collisions is a monumental challenge. As new buildings are built every year, the threat to birds increases. Architects and specifiers can play a major role in curbing the problem by exploring glazing solutions specifically engineered to be bird-friendly.

Biologists are continuously refining testing systems to help the architectural industry make informed decisions when choosing a glass solution, as new bird behavioural research continues to help expand the knowledge base.

The architecture and building design industry is perhaps best positioned to press for long-term technological solutions for bird safety. The glazing industry has responded with innovative new products to help solve the problem. Esthetics and cost are two challenges, but they are continually met with new ideas from the glass industry. As technologies work to make glass noticeable to birds without obscuring or distorting views through glass, and as humans visualize and use the material, bird-friendly cities are likely to be on the horizon.

Notes

¹ See Sheppard, Christine D. “Glass Collisions: Why Birds Hit Glass,” https://abcbirds.org/glass-collisions/why-birds-hit-glass/[6].

² Read Sheppard, Christine D. “Evaluating the relative effectiveness of patterns on glass as deterrents of bird collisions with glass.” Global Ecology and Conservation, vol. 20, 2019, https://doi.org/10.1016/j.gecco.2019.e00795[7].

³ Visit “American Bird Conservancy Doubles Its Capacity to Test Bird-Friendly Glass.” ABC Press Release, March 24, 2022, https://abcbirds.org/article/bird-collision-testing-tunnel-md-launch/[8].

⁴ Refer to the American Bird Conservancy. “Bird Collision Deterrence Material Threat Factor Reference Standard.” https://abcbirds.org/wp-content/uploads/2020/09/ABC-Material-Threat-Factor-Reference-Standard-draft-9-29-2020.pdf.[9]

[10]Author

Julia Schimmelpennigh is the architectural industry technical manager for the advanced material interlayers business at Eastman Chemical Company. She has more than 30 years’ experience in lamination and laminated glass applications support. Schimmelpennigh provides technical product support to glass fabricators, architects, designers, engineers, and specifiers. Her work includes new product development, qualification, and commercialization of laminated glazing solutions, regulatory development, industry education, and association support. Schimmelpennigh is an active contributor in the glazing industry as a member of ANSI, ASTM, CGSB, ISO, GICC, NGA, and other organizations. She received the highest award given by ASTM International for her contributions to the industry and was designated as an honourary fellow and the prestigious C.G. Carney Award from the National Glass Association (NGA).

Source URL: https://www.constructioncanada.net/bird-safe-glass-codes-and-standards-to-know/

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