What is Bird-Friendly Glass?
Glass facades deliver many benefits including daylight, views and dynamic aesthetics. A counterpoint is that birds do not perceive traditional clear glass as an obstacle to their flight path. It is possible to balance glass building benefits with the adverse impact on birds by selecting glass that can take advantage of its many benefits while also minimizing the potential for bird to glass collisions.
Research has shown that adding a pattern can increase a bird’s ability to perceive glass, thus reducing the likelihood of a collision. This awareness has lead organizations, cities and states to develop bird-safe building guidelines, laws and official standards that apply to architectural glass and buildings.
As a glass fabricator, Viracon has been actively involved in the ongoing bird friendly glass research, focusing specifically on finding practical solutions using conventional glass products for buildings with applied patterns. Additional information about the research and testing is available in the Tech Talk.
Tested Products and Threat Factors
Scores from the American Bird Conservancy (ABC) tunnel test are utilized by ABC and the U.S. Green Building Council® (USGBC) to assign a threat factor for each tested material. A lower threat factor means that the product deterred more birds in the tunnel test than a product with a higher threat factor. Viracon has six products for your architectural project that have been tested by ABC.
Threat Factor 6
Color: V958 Dark Gray Viraspan
Pattern: 1/8” horizontal lines alternating with 1/2” spaces (screen 2256); 20% coverage
Threat Factor 24
Color: V951 White
Pattern: 1/8” dots (screen 5006); 40% coverage
Threat Factor 10
Color: V953 Medium Gray Viraspan
Pattern: 1/8” vertical lines alternating with 1/2” spaces (screen 2256); 20% coverage
Threat Factor 17
Color: Digital White and Digital Etch (every other line switches between the colors)
Pattern: 1/8” horizontal lines 2” on center (screen 2824); 6% coverage
Threat Factor 41
Color: V951 White
Pattern: 1/8” dots, 1/4” on center (screen 5065); 20% coverage
Threat Factor 29
Color: Digital White and Digital Etch (1/8” etch lines and 1/16” white white)
Pattern: alternating 1/8” and 1/16” horizontal lines all 2” on center; 5% coverage
Researchers acknowledge it isn’t practical to test every pattern. To address this practicality, researchers have used existing research to develop a guideline commonly referred to as the 2x4 Rule. The 2x4 Rule is referred to in multiple bird-friendly design guidelines and indicates that developing patterns with horizontal lines spaced no more than 2” apart or vertical lines spaced no more than 4” apart can deter collisions.
Color: All colors meet the 2x4 Rule
Pattern: 1/8" vertical lines, 4" on center (screen 20566)
While using the 2x4 Rule can deter collisions, reducing the spacing to 2” in both directions may protect small songbirds that will fly through a 4” gap.
Viracon has participated in numerous projects that utilized printing to reduce the likelihood of bird collisions. These projects utilized patterns, many of them customized, to meet the needs of the specific guideline, standard or law required by the project owner or design team.