On July 1, 2024 CALGreen’s Intervening Code Cycle update went into effect, adding new mandatory measures addressing embodied carbon for some large nonresidential projects and updates to EV parking requirements. It also introduced a new voluntary Tier 1 measure regarding bird-friendly building design. There is a clear connection to the LEED Innovation in Design credit: Bird Collision Deterrence. When measures start showing up in both the CALGreen Code and LEED, it can be an indication that they address some best practices and that in the future may be moving toward a mandatory measure; especially in this case, where it was deemed important enough to add prior to the 2025 code release.
Hundreds of millions of birds die each year in the United States due to collisions with buildings, and many more are injured. More glazing is being seen in all types of construction, from tall skyscrapers to residential projects. With that increase in glass, bird collisions are on the rise. The goal of bird-friendly design is pretty self-explanatory, incorporate features into the building design that reduce bird injury and mortality from in-flight collisions with buildings. CALGreen aims to provide a uniform guideline for bird-friendly building standards for the planning and design processes. The idea is to utilize strategies that make the built environment safer for birds without totally obstructing occupant views and connections to the outdoors.
Large pane of glass appearing to be a pathway (Source: American Bird Conservancy, Bird-Friendly Building Design)
To understand what strategies are effective, we need to understand what site elements and glazing properties create risks for birds. First, a building’s lighting, both interior and exterior, can disorient birds and impact visibility for those that migrate at night. LEED requires projects to meet the uplight and light trespass requirements in the Light Pollution Reduction credit. CALGreen requires nighttime lighting at the top of the building and in the interiors of all areas visible through exterior glazing to be controlled with time-switch control devices or occupancy sensors.
A second hazard pertains to glazing properties, where reflections and transparency can make it hard for birds to realize they are flying toward windows, rather than pathways to more vegetation. Lighting and time of day can affect the appearance of that glass.
To mitigate these hazards, CALGreen voluntary measure requires treatment to:
· At least 90% of glazing on a building elevation between grade and a height of 40 feet AND
· At least 60% of glazing on a building elevation from 40 feet above grade to the top of the building elevation.
Similarly, LEED breaks down the building façade into:
· Façade 1, the first 40 feet above grade and 12 feet above any green roof
· Façade 2, all façade areas between 40-100 feet.
Rather than requiring a percentage of the glazing needing treatment, LEED uses a calculation based on material areas and material threat factors to determine the total building Bird Collision Rating. In addition to glazing on the building façade, LEED also addresses handrails, guardrails, windscreens, noise barriers, gazebos, pool safety fencing, bus shelters, band shells, and other structures.
Strategies that minimize the risk of birds colliding with buildings can either be directly on the glazing or on other features that create a visible barrier. Some of those include:
Glazing visual markers:
Etched or fritted glass with patterns no more than 2 inches apart
Interior or exterior glazing film with 2”x2” visual markers
Laminated glass with 2”x2” visual markers, patterned Ultraviolet (UV) coating or use of contrasting patterned UV-absorbing and UV-reflecting films
Glass block or channel glass
Other developed glazing technologies documented to reduce bird strikes, tested by an independent third party and approved by the authority having jurisdiction
Slats, screens, netting, louvers:
Horizontal or vertical slats of 1/8” minimum face width with minimum 2” spacing that obscure 85% or more of glass
Grilles, screens, or 1/8” diameter welded wire mesh with openings no more than 2” maximum horizontally and vertically
Netting with 1” maximum openings
Sunshades or louvers 9” deep vertically spaced a maximum 9” or 6” deep horizontally at maximum 6” spacing
Many of these strategies follow the 2” x 2” Rule which, derived from research on songbirds, found that horizontal or vertical lines two or fewer inches apart tend to deter birds from colliding with buildings. This can be seen in the examples below from the American Bird Conservancy’s Bird-Friendly Building Design Guide resource.
From left to right they are: Philadelphia Zoo Bear Country exhibit with window film; Consilium Towers, mirror-glass complex in Toronto, with Feather Friendly dot pattern; and Ornilux Mikado’s pattern reflects UV wavelengths that birds are sensitive to. The spiderweb effect is visible to humans only from very limited viewing angles.
Bird-friendly building design is a reminder that our built environment is an extension of the environment around us, not separate from it. We must remember the impacts our buildings have to the wildlife around us and do what we can to mitigate damage.
For the full code language, please reference the CALGreen Code Section A5.107 Bird-friendly building design and the LEED Innovation: Bird Collision Deterrence credit language. Resources like the American Bird Conservancy and the National Audubon Society have more information regarding effective bird-friendly strategies.
