Article written by Joanna Matei, RA, Associate
Glass is a major component in all buildings. Allowing natural light into the built interior improves human health, however it does the opposite for birds flying by. Birds, both native and migrant, often fly into glass. This is because glass reflects the sky and nearby trees. Birds can't distinguish between reflection and reality. Birds will also try to fly through glass, such as the guardrail of a vegetative roof terrace. Interior lighting can confuse migrating birds at night, causing them to fly in circles and often die of exhaustion.
Yellowthroat migratory bird
The bird population is declining, New York Audubon estimates hundreds of thousands of birds die annually in NYC from colliding into windows. New York City took the initiative to be on the forefront of taking initiative in helping preserve the bird population by passing New York City’s Local Law 15. It outlines bird friendly building design and construction requirements. It applies to all new construction and full glazing replacement on alterations. Specific requirements are as follows:
Bird friendly materials must be installed from grade to 75' above grade on exterior wall envelope and fly-through conditions.
Bird hazard installation such as glass awnings, glass handrails and guards, glass wind break panels, or glass acoustic barriers, must be constructed of bird safe materials regardless of height.
Bird friendly materials are also required when glazing is adjacent to a green roof system up to 12 feet above the walking surface.
Image courtesy of Guardian Glass
Per NYC LL15, bird friendly materials must have a threat factor of 25 or less in accordance with the American Bird Conservancy Threat Factor. Patterns must be spaced apart no greater than 2" x 4". Bird safe patterns applied onto the first surface of the glass easily meet the threat factor as are not hidden by reflection. Patterns can be applied in three different ways:
1. UV coated, virtually invisible to the human eye, thus least impact on aesthetics.
2. Acid-etched patterns are applied directly into the glass and are translucent.
3. Fritted patterns are opaque and most visible to the human eye.
Gertler & Wente Architects worked closely with Guardian Glass in selecting bird friendly glass for a full glazing replacement project in NYC. Guardian offers a UV pattern and many etched patterns which meet NYC Local Law 15 requirements. We were able to select from a number of Guardian glazing units which when combined with the patterns have an approved threat factor. Approved glass to which patterns can be applied to have lower visible light reflection, otherwise the patterns would not be visible to birds.
Gertler & Wente Architects is excited to educate future clients and apply bird safe materials into future projects, creating a safer environment for wildlife.