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Bird friendly glass

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Each year, millions of birds accidentally fly into glass windows, doors and facades, with many of these collisions being fatal. As glass continues to make up more and more of the external building envelope, it is likely that the number of birds affected by this problem will increase over the coming years. Building requirements are becoming more stringent across the world, which means architects are now looking for glass solutions that are safer and which help to reduce the risk of bird collisions, whilst still providing the aesthetic and performance attributes that their projects require.

Attempts to reduce these types of collisions have included adding visible shapes or printed dots to the glass – with positive results. However, the appearance of the glass suffers when patterns or dots are printed on the glass.

Why do birds collide with glass?

The two most common causes of birds colliding with glass are its transparency and its reflectivity.


The transparency of glass is perhaps the most well known cause of bird collisions. The bird sees the tree, the sky or an attractive landscape through the glass and flies directly towards it, colliding with the pane of glass in the process. This danger is increased as the transparency of the glass increases (and size of the glazed area).



Another cause of bird collisions with glass is reflectivity. The type of glazed surface, the light and the environment behind the glass all determine how strongly and how clearly the surroundings are reflected. If a park environment is reflected, the bird may be deceived into thinking it sees a pleasant location. It flies directly towards it, without realising that this is only a reflection in the the glass. Reflective surfaces placed in the landscape have the same effect.


Reducing Reflectivity to less than 15%

The degree of external reflection of glass panes and the design of the surrounding environment are critical. Even moderate levels of reflectivity can pose a danger to birds, particularly when the room behind the glass is dark. Reducing dangerous reflections is a challenge because variable light conditions affect reflectivity. How- ever, choosing glass with a low coefficient of reflection is a step in the right direction.

Reducing Reflectivity to less than 15%

Ornithologists1 recommend that in order to reduce the dangers of reflectivity, glass (double or triple glazing) with an external coefficient of reflectivity of 15% or less should be installed. Such glazing is not completely safe, but for particularly large surfaces, it is an economically attractive and acceptable solution that does not reduce visibility compared to patterned glass.

1 “Bird-Friendly Building with Glass and Light”, Hans Schmid, Wilfried Doppler, Daniela Heynen & Martin Rössler (Swiss Ornithological Institute Sempach, 2013).

Guardian Glass Solutions

Guardian Glass offers a range of solutions answering bird friendly glass requirements for double and triple IGUs (insulating glass units) with external reflectivity of 15% or less. These solutions provide architects with the good balance between transparency and reflectivity. Compared to traditional glass solutions that utilise printed dots or visible shapes, Guardian glass solutions provide architects with high performance, optimal light transmission and clear views of the outside environment. Furthermore, these glass solutions offer enhanced aesthetics that are consistent with the rest of the glazed façade, with no additional surface treatment required or costs involved. This means architects do not have to compromise on the appearance of the glass when choosing bird-friendly solutions. Guardian Glass offer a range of products within its SunGuard portfolio that meet the requirement for bird friendly glass.

Guardian System TEA (True Edge Application)

For higher requirements, a marking can be applied at least on surface #2 of the glazing. An ideal solution for this is the enamel Guardian “System TEA” for ceramic printing of black marks directly onto the coating. As this enamel dissolves the coating (and its reflection) a maximum contrast can be achieved when looking from out- side on the glass.