Our team is attempting this credit and it appears that the bird threat rating calculation does not include any type of tools to determine the threat of an angled glass which was designed to reflect a light colored concrete, as ours was. There is documentation on bird-safety websites to support the use of this method. Does anyone know of an effective way to document this?
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Theresa Backhus
Sites Technical Specialist, LEEDUSGBC
66 thumbs up
February 16, 2012 - 4:09 pm
Hi Trinidee,
I have consulted the subject matter expert that helped draft this pilot credit for the answer to your question.
The original idea that angled glass might reduce collisions mortality was derived from the article titled "Effects of Window Angling, Feeder Placement, and Scavengers on Avian Mortality at Plate Glass" by Daniel Klem, Jr in 2004. However, since then, a number of advancements in this field have been made. Klem no longer believes that angled glass is a useful solution in most circumstances, and the Bird-Safe Glass Foundation and American Bird Conservancy concur. It is unfortunate that the strategy is still on various websites, but as you know, it takes a long time for websites to get updated.
The original two thoughts on angled glass were: 1) birds hitting glass at more or less than a 90 degree angle experience less impact and 2) angled glass reflects the ground, so it is not attractive. However, these theories have proven incorrect. For example, even if angled glass reflects a parking lot, birds fly through parking lots and into reflections of parking lots, and they can approach the glass at any angle (as opposed to the situation in the paper where birds flew directly from a feeder to nearby glass on a trajectory more or less parallel to the ground).
So the short answer to your question is that it was intentionally left out of the calculation. I hope this helps.
Mike Barker
Principal : Energy / Electrical EngineerBuildingPhysics South Africa
150 thumbs up
May 2, 2012 - 2:25 am
Angled glass may not completely reduce the "Threat Factor" to 0, but it may reduce it to a number less than 100 ? It therefore does not make sense to ignore the possible reduction in bird strikes that angled glass can provide ?
Going one step further, and in the interests of helping us all learn more about this issue, would your subject matter expert be able to provide a list of peer reviewed research papers that support the argument that angled glass provides absolutely no reduction in bird strikes at all ?
Let me add that angled glass is a useful method to reduce solar heat gain, and if it also reduced bird strikes that would be a bonus ? ( in some parts of the world angled or sloped glass is known as "poor mans" low-e glass )
Trinidee Shelton
15 thumbs up
May 3, 2012 - 1:18 pm
Even though the angled glass was not included as part of the calculation, I believe it does warrant further research and potential application. Due to the nature of an urban setting, it appears that angled glass may not have much effect above a certain height, based on my research and applications. However, the project we applied this system to was in a rural setting, for a visitor's center to a National Wildlife Refuge in Texas. It has proven to be an effective application based on decreased bird strikes compared to previous years on the same property with existing structures. This refuge is the home of hundreds of species of birds and is within view of a lake. We documented the decreased bird strikes and showed, through section views, that approaching birds would see very little reflected sky. We did achieve this credit, but it appears that the angled glass would need to be on a case-by-case basis. Hope this is helpful.
Mike Barker
Principal : Energy / Electrical EngineerBuildingPhysics South Africa
150 thumbs up
May 4, 2012 - 2:16 am
Likewise, the facade in question is at ground level in a rural area, and in front of ground that rises away from the building.
It is a factory with a nearby small artificial wetland and it seemed that some effort should be taken to reduce birdstrikes, although the main reason for the angle is to reduce solar heat gain. We were, at that stage, not aware of any LEED Credit.
We have fisheye photographs taken from a number of points that show very few reflected views of the sky, unless the bird is flying up from the ground directly in front of the facade. In this case we don't believe the bird could achieve it's full flying velocity and hence any impact would be reduced.
We believe that while the angled glass will not stop all birdstrikes, it should still reduce the probability ?
A reflected image of the ground must have at least a similar effect to that of, say, white ceramic frit with 1/8" dia. dots w/20% coverage ?
Once again, this LEEDuser.com forum provides a useful opportunity to debate these issues. We do need the ability to post JPGs though - a pic is worth a 1000 words.