Modern-day architects have an affinity for buildings covered in glass, however this design choice has the unfortunate effect of increasing accidental bird deaths.
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The United States fish and wildlife service has estimated that over ~750million birds die as a result of flying into glass facades, after finding it difficult to differentiate this glass from open airspace.
The Glass Used In High Rise Buildings
The glass used in high-rise buildings or skyscrapers is resilient and fabricated so that it does not easily shatter. Besides this, this glass has to be transparent, have visible transmittance, high workability, a lower UV value, and most importantly it must be a recyclable material.
The glass used in high-rise buildings is composed of two pieces, each of which is 6mm thick and separated by a half-inch of air space, creating a total one-inch-thick unit. The half-inch section of air space is used to prevent fogging and is sometimes packed with argon in cold climate areas. The glass to be used in high-rise buildings is heat strengthened rather than tempered, because tempering glass compromises the optical quality of the glass.
The glass in high-rise buildings has to be tinted to reduce the heat gain from the sun while it remains insulated to retain the heat. The glass also needs to maintain a balance between how much light is allowed into the buildings while protecting the building from ultraviolet light privacy.
Glass can be very appealing to the eye, but security and privacy have to be taken into account when selecting the correct glass for the building. Full or partial frosting can be done to increase privacy.
Techniques Implemented to Prevent Bird Deaths
Although impractical, homeowners can help reduce bird collisions by removing plants from windows, installing screens, or placing tightly stretched nets at a distance from windows.
Guy Maxwell, a partner at the New York-based Ennead Architects and also a bird lover, has been on a mission to mitigate the death of birds by collision into glass. Guy Maxwell with the help of other anti-collision advocates like the American Bird Conservancy, has made some notable progress on bird-safe building regulations, bird safety awareness, bird-safe glass, etc.
The research by Guy Maxwell and his colleagues has revealed some notable information such as that birds will not fly through vertical lines that are placed no more than 4 inches apart, and that line patterns are more effective in collision prevention than dots. The Enneads research lab, the first of its kind with tunnel testing provisions, is spearheaded by the American Bird Conservancy Collision manager Christine Sheppard. The research by Guy Maxwell and Christine Sheppard has been relayed to glass manufacturers like Guardian, Viracon, and Bendheim to help in the production of glass that will be visible to birds in flight.
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To increase the visibility of glass to birds, dots, lines or other patterns can be painted on the exterior of the glass. Ultraviolet designs can also be coated onto the glass. This is because birds can see the visible ultraviolet portion of the electromagnetic spectrum. This is not a perfect method, but when humanely tested it has proven that 67% of the time birds can avoid the UV patterned glass as opposed to ordinary clear glass.
To make non-reflective glass, the glass must be textured, fritted, or etched. Texturing of glass will involve patterning semi-molten glass or engraving to produce a less reflective and translucent surface.
A frosted surface can be produced by acid etching. Fritted glass is produced by the screen printing of an ink-like nanoparticle that is called a frit, followed by heating of the glass to 620’C to fuse the frit onto the glass surface. This produces an opaque and less reflective type of glass.
Other achievements by this group came in 2011, when in partnership with the US council when they launched the LEED pilot credit number 55 to incorporate ‘’ bird collision deterrence’’ into newly constructed buildings. The aim was to allow buildings to become as visible as possible to the birds with the help of technologies such as exterior building louvers or screens and decreased levels of night light.
A real threat exists to birds as a result of glass collisions, and more and more architects are becoming aware of this fact and are now incorporating bird-friendly glass in their buildings. This is despite it being 5% more expensive than ordinary glass. Increasingly, more policies around the world are being put in place to mitigate bird-glass collisions.
Further Reading and Reference
Nast, C., 2016. How to Keep Buildings From Killing Hundreds of Millions of Birds a Year. [online] Wired. Available at: <https://www.wired.com/2016/11/keep-buildings-killing-hundreds-millions-birds-year/>
Editors, A., 2022. Bird-friendly glass for reducing collision mortality. [online] Accessscience.com. Available at:<https://www.accessscience.com/content/briefing/aBR1123211>
Klem Jr, D., 2009. Preventing birds–window collisions. The Wilson Journal of Ornithology, 121(2), pp.314-321
BuilderSpace. What Kind of Glass Is Used in High-Rise Buildings?. [online] Available at: <https://www.builderspace.com/what-kind-of-glass-is-used-in-high-rise-buildings>
Madison Audubon. n.d. Bird-Safe Glass — Madison Audubon. [online] Available at: <https://madisonaudubon.org/bird-safe-glass>