The Invisible Threat: Creating bird-friendly buildings

Bird-friendly glass products
Some members of the glass industry are actively developing glass products that will reduce bird collisions, with several already available in North America. These products fall into three general categories: fritted, UV-reflective, and etched.

Fritted glass
Fritted glass (i.e. conventional glass with baked-on ceramic patterns) effectively reduces bird collisions. These patterns can take the form of dots, stripes, or any other shape. Striped patterns can be more effective than dotted patterns, with less coverage. However, in most conventional fritted glass, the frit is applied to what is called the #2 surface—the inside face of the outer pane. This is not as visible as if the frit were applied to the #1 surface—outside face of the outer pane—where it is exposed to weather. Several European manufacturers are now willing to warrant fritted glass with the frit on the #1 surface where there have been problems in the past related to wear ability. North American manufacturers need to do the research and development necessary to create this, and make it available to help reduce bird collisions.

CC_Jan_14_HR-36-2UV-reflective glass
As noted, birds can see UV light, but humans cannot. This is the principle behind UV-reflective glass. One product offers glass with a UV-reflective twig pattern applied as a coating on the #2 surface. The pattern is nearly invisible to humans, but can be seen by birds. This product has been used for several years in Europe, but only recently in a few North American locations. This too needs to develop the technology to allow it to be placed on the #1 surface to overcome reflections and allow for high-performance coatings to be placed on the #2 surface in order to meet energy requirements.

Etched glass
A newly developed Canadian glass places acid etched patterns on the #1 surface, thereby ensuring the treatment is visible to birds, whether in a reflective or transparent mode. It is currently available in regular or random spaced stripes of several designs conforming to the 2×4 rule.

Retrofit solutions
In existing situations where replacement of glass is cost prohibitive, several products are available as a surface treatment. UV films, decals, die-cast patterns, and tapes are readily available and can be applied to the outside of glass. Some are designed to last up to 10 years and are highly effective in reducing collisions. Often, they need to only be applied to areas of the glass where bird impacts are common. If applied with an eye to esthetics, these treatments can be architecturally pleasing with little loss of visibility.

Measuring effectiveness
Many of these glass and film products have been tested in experiments using live birds. Typically, the birds are released in a 7.3-m (24-ft) long tunnel with two types of glass at the end: a control panel (clear), and the panel to be tested. The test glass is rated by the percentage of birds who avoid it and fly toward the clear glass. (Most protocols include a protective net preventing the bird from actually hitting the glass, and each bird is used only once.)

Ratings based on these tests are summarized in Bird Collisions Deterrence: Summary of Material Threat Factors, which was developed in 2011 by the American Bird Conservancy and used as the basis for LEED pilot credit evaluations. In this system, opaque material is rated ‘0’ (i.e. minimum threat) and clear glass is rated ‘100’ (i.e. maximum threat). Tested products receive a rating depending on their effectiveness.4

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