An estimated 1 billion birds die annually in the United States as a result of striking buildings, bridges, and other manmade structures. Many factors play a role, including lights, vegetation, and water. But glass is the main culprit, according to bird-safe design guidelines released in 2007 by the New York City Audubon Society, the Chicago Birds & Buildings Forum, and the City of Toronto. Because birds do not perceive conventionally formulated glass as a solid barrier, they fly into it. They may mistake reflections as continuous space and be attracted to trees or other objects in, or visible through, a glassed-in space.
This credit is largely an appeal to enlightened self-interest, saving birds while reaping the financial benefits of green building. A number of cities are pushing “bird-safe” design, although mostly as a recommendation. Toronto may adopt green building requirements that include bird safety criteria, and in Manhattan the environmental impact statement for the reconstruction of the World Trade Center addresses bird safety. A handful of top designers have made it a priority, but advocates note that it’s far from a mainstream design consideration.
The credit emphasizes creating “visual noise”- i.e., patterns that birds can register. Strat- egies to create patterns on glass include using color, texture, opacity, or ultraviolet materials that are visible to birds. Keeping openings small and reducing the quantity of glass on each façade will correspondingly lower the incidence of bird strikes.
If all materials on the building have a Threat Factor of 15 or below and the project did not perform the calculations, submit a narrative describing why the materials, and building in general, are “bird-friendly.” This includes a material list and supporting data.
A completed Bird Collision Threat Rating spreadsheet.
Plan(s) and/or elevation(s) depicting the location of all materials and shading/screening devices used to comply with this credit
Applicable specification details on all materials and shading/screening devices used to comply with this credit
A copy of the building operations guidelines text that stipulates that all interior lighting must be turned off by the appropriate nighttime personnel after hours when the space is unoccupied.
Narrative, and drawings showing control locations, describing the lighting controls used on the interior lighting, the sequence of operation and how these controls comply with this credit and section 9 of the ANSI/ASHRAE/IES Standard 90.1-2010
A photometric report of those luminaires demonstrating that no light is emitted above 90 degrees from straight down in their final installed position(s).
Narrative, and drawings showing control locations, describing the lighting controls used on the exterior lighting, the sequence of operation and how these controls comply with this credit.
All submittals required for the LEED for New Construction SS Credit, Light Pollution Reduction.
A copy of the post-construction monitoring plan
Provide all Submittals listed under Interior Lighting in NC, CS, Schools, Retail, Healthcare above.
Provide all Submittals listed under Interior Lighting in NC, CS, Schools, Retail, Healthcare above.Exterior Lighting
Provide all Submittals listed under Exterior Lighting, Option 1 in NC, CS, Schools, Retail, Healthcare above.
Provide all Submittals listed under Exterior Lighting, Option 2 in NC, CS, Schools, Retail, Healthcare above.
Provide all Submittals listed under Post-Construction Monitoring Plan in NC, CS, Schools, Retail, Healthcare above. Provide records of all collisions during the Performance Period. Include the location, date, and approximate time of day for each collision.
Plan(s) and/or elevation(s) depicting the location of all temporary and permanent materials and shading/screening devices used to retrofit the building facade in response to the results of the monitoring plan.
Applicable specification details on all temporary and permanent materials and shading/screening devices used to retrofit the building facade in response to the results of the monitoring plan.
The following flowchart gives a visual explanation of the credit requirements for New Construction, Core & Shell, Schools, Retail: New Construction, and Healthcare projects pursuing this credit:
A building design that deters bird collisions will allow for most any type of site landscape design. Although the proximity and height of landscape material have shown to influence the number of bird collisions, if the building facade is designed to be “bird-friendly”, the landscape material will not reflect and cause confusion to birds.
Atria lighting is addressed in the Interior Lighting requirements, and should follow the same shutoff procedures as other interior spaces with a direct line of sight to the exterior fenestration. Lighted building atria are major causes of nighttime bird collisions, so it is important that larger lit spaces are shutoff during the specified times. This is especially important during migration seasons in the spring and fall.
The monitoring should include a plan to routinely monitor the effectiveness of the building design in preventing bird collisions. Monitoring (which includes walking the perimeter before normal business hours or at night, geotagging photographs of dead or injured birds, or other similar strategies) should occur twice a week at minimum. It is advisable that the monitoring be done prior to 8 or 9 am, and that it occurs daily during peak migration seasons. Monitoring works best if the building is divided into easily identifiable segments, facades, or portions of facades so that the relevant location of the collision can be easily identified. Monitoring should be linked to standard building maintenance as much aspossible, thereby becoming routine and requiring minimal extra effort and cost. The more data collected, the better the resulting retrofits (if any) will be. Teams can use their own monitoring plan, or an “out-of-the-box” solution, whichever is more appropriate. See the Resources section for more information on developing a monitoring plan.
For a general outline of applicable building materials and their threat factors, see this Summary of Material Threat Factors. Teams can find the necessary, detailed data (mate- rials that comply with the requirements and associated threat factors to use in the BCTR calculations) from ABC’s website and the Resources section of this document. Below is an example Bird Collision Threat Rating calculation that meets the Building Facade Requirements.
Facade Zone 1
Calculate the Facade Zone 1 BCTR
[((Material Type 1 Threat Factor) x (Material Type Area)) + ((Material Type 2 Threat Fac- tor) x (Material Type Area))...] / [Total Facade Zone Area] = Facade Zone BCTR
[100 x 560) + (20 x 816) + (0 x 11940)] / 13316 = 5.43 (Facade Zone 1 BCTR)
Facade Zone 2
Calculate the Facade Zone 2 BCTR
[((Material Type 1 Threat Factor) x (Material Type Area)) + ((Material Type 2 Threat Factor) x (Material Type Area))...] / [Total Facade Zone Area] = Facade Zone BCTR [(100 x 0) + (20 x 7209) + (0 x 23645)] / 30854 = 4.67 (Facade Zone 2 BCTR)
Determine the total building BCTR
[((Zone 1 BCTR) x 2) + (Zone 2 BCTR) ] / 3 = Total Building BCTR
[(5.43 x 2) + 4.67] / 3 = 5.18 (Total Building BCTR)
The following flowchart gives a visual explanation of the credit requirements for ExistingBuildings: Operations & Maintenance projects pursuing this credit:
EBOM projects differ from new construction projects in that the building facade characteristics are already in place when projects begin. Therefore, there are fewer opportunities to design new building facade elements that deter bird collisions. The EBOM requirements recognize the unique nature of existing buildings, and stipulate that a monitoring plan should be created to first observe and document bird collisions, then take corrective action to mitigate any collisions that occur. Along with the monitoring plan, interior and exterior lighting requirements should be met.
Excerpted from LEED 2009 for New Construction and Major Renovations
Reduce bird injury and mortality from in-flight collisions with buildings.
Comply with one of the Building Façade options, one of the Interior Lighting options, one of the Exterior Lighting options, and the Post-Construction Monitoring Plan requirements below.
Develop a building façade design strategy to make the building visible as a physical barrier and eliminate conditions that create confusing reflections to birds. If all materials on the building façade have a Threat Factor of 15 or below, the project is exempt from the building façade requirements and the following Bird Collision Threat Rating calculations are not required.
If any material on the building façade has a Threat Factor above 15, then the Bird Collision Threat Rating calculations are required. First separate the building into Façade Zone 1 or Façade Zone 2. Façade Zone 1 includes the first 3 floors above ground level, as well as 1 floor above any green roofs. Façade Zone 2 includes all façade areas above the 3rd floor. Then identify the Material Types present on the building façade and the Threat Factor of each type (for detailed material types and associated threat factors, see the Bird Collision Deterrence: Summary of Material Threat Factors table developed by the American Bird Conservancy). Determine the total area of each Material Type.
No more than 15% of the glazed area in Façade Zone 1 can have a Threat Factor higher than 75. However, more than 15% of the glazed area in Zone 2 may have a Factor higher than 75. All glazed corners or fly-through conditions must have a Threat Factor less than or equal to 25.
Using the formulas below, achieve a maximum total building Bird Collision Threat Rating (BCTR) of 15 or less.
First, for each Façade Zone, perform the following calculation:
[((Material Type 1 Threat Factor) x (Material Type Area)) + ((Material Type 2 Threat Factor) x (Material Type Area))…] / [Total Façade Zone Area] = Façade Zone BCTR
Then determine the total building Bird Collision Threat Rating by performing the following calculation with the Zone 1 and Zone 2 BCTRs:
[((Zone 1 BCTR) x 2) + (Zone 2 BCTR) ] / 3 = Total Building BCTR
Develop a lighting design strategy to effectively eliminate or reduce light trespass from the building. The lighting in all spaces with a direct line of sight to exterior fenestration shall meet at least one of these two options:
Include a requirement in any building operations guidelines stating that all interior lighting must be turned off by the appropriate nighttime personnel after hours when the space is unoccupied, or at a minimum from midnight until 6 a.m.
The lighting shall be controlled such that all lighting in the space will be automatically shut off after being vacant for a period of no longer than 30 minutes.
Develop a lighting design strategy to effectively reduce or eliminate light trespass from exterior fixtures. Meet the exterior and garage lighting power density and controls requirements in sections 188.8.131.52, 184.108.40.206, 9.4.3, of the ANSI/ASHRAE/IES Standard 90.1- 2010 (with errata but without addenda).
Shield all exterior fixtures such that the installed fixture does not directly emit any light at a vertical angle more than 90 degrees from straight down. Exterior building fixtures that are not necessary for safety, building entrances, and circulation shall be automatically shut off from midnight until 6 a.m.
Demonstrate that the project complies with the exterior lighting requirements of the latest published LEED for New Construction SS Credit, Light Pollution Reduction.
Develop a three-year post-construction monitoring plan to routinely monitor the effectiveness of the building design in preventing bird collisions. Include methods to identify and document locations of the building where repeated bird strikes occur, the number of collisions, the date, the approximate time (if known), and features that may be contributing to collisions. The plan should also provide a process for corrective action.
Register for the pilot credit
Post-Construction Monitoring Plan
EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems. PROJECTS
The homepage for the LEED Pilot Credit Library. The LEED Pilot Credit Library is intended to facilitate the introduction of new prerequisites and credits to LEED. This process will allow USGBC to test and refine credits through LEED 2009 project evaluations before they are sent through the balloting process for introduction into LEED.
A national leader in reducing human impacts on birds and wildlife. ABC’s bird collision program supports national efforts to reduce bird mortality through education and advocacy. The ABC website includes:
A database with photographs that provide visual guides to designing “bird-friendly” build- ings and building features, and choosing appropriate materials. It will be periodically updated.
An example of a post-construction monitoring plan to monitor the effectiveness of the building design in preventing bird collisions.
A table that lists detailed material types and
associated threat factors for use in calculating the Bird Collision
This Chicago-based non-profit supports more “bird-friendly” design through education and advocacy. Their website maintains lists of organizations and resources.
One of the first cities to implement a mandatory lights-out program, Chicago’s Depart-ment of Environment has many resources for “bird-friendly” design.
CyberTracker is a free, GPS-based application for collecting and recording field data. It can be used to track species, locations, photographs, and other observations.
Background for the LEED Pilot Credit Library is provided in this foundational document.
What is the process to have additional materials submitted, approved and added to the Bird Collision Deterrence: Summary of Material Threat Factors document?
I am editing this question to hopefully make it more clear.
Our project is hoping to achieve Bird Collision Deterrence. We have a question on the spreadsheet calculations. If the entire building facade is classified as Zone 1 (it is a single story building), when using the BCTR Spreadsheet should we use the Z1 BCTR output as the Total Building BCTR or the Total Building BCTR calculation? The Z2 BCTR does not work when its material area is set to 0, which in turn means the Total Building BCTR formula does not work. However, if I manually set the Z2 BCTR to 0 in the Total Building BCTR formula, it does work, and effectively reduces the Z1 BCTR by 1/3 to reach the Total BCTR. Which is the correct number to use?
If the entire facade is in Zone 1, you can use the Z1 BCTR output as the Total Building BCTR.
Thank you for the reply Theresa. I'm going to push just a little harder on the question, because the difference in using the Z1 BCTR output is significant when compared to using the Total Building BCTR. I want to clarify if "can" means "must." To illustrate, if I take the exact same building as my current project and build a 3-story solid tower on top I end up with a Z1 BCTR of 15.89 but a Total Building BCTR of just 10.60. Yet by adding a solid tower, I probably haven't made the building more or less bird-friendly. Does that make sense? I'm sure there are other ways to think about it than what I just presented...just trying to figure out the most logical way to break it down.
Our intention is to pursue Bird Collision Deterrence under NC. Several questions:
1. Do I interpret the credit requirements correctly in saying there would be no actual retrofitting requirements under NC? The basis for the monitoring plan is to record actual bird collisions to determine effectiveness of the implemented design measures, but defining corrective, retrofitting measures is not required to receive the LEED design credit?
2. Also, regarding the monitoring plan, I don't see a specific threshold defined, in terms of the number or rate of collisions recorded, that would trigger the requirement for retrofitting. 1 collision per day, week, month, year?
I am preparing to submit for review, and am trying to complete the documentation for this credit. I have the confirmation email where I signed up for the credit, and have completed the feedback survey (yesterday afternoon), but have yet to receive a confirmation email for completing the survey. The project website indicates that a copy of the "survey completion email" is required to complete documentation. I have the other required documentation, and am otherwise ready to submit, except for the survey email. Can you tell me how long it takes USGBC to send that confirmation email? I have checked my Inbox and junk folder, just in case, but nothing has arrived. As a backup, I took a screenshot of the survey completion confirmation that showed up after I submitted the survey.
Would it be ok to upload the screenshot if the email does not show up? This is the only credit we are waiting on to be able to submit (the client is anxious). Please advise.
Can anyone advise on this? We cannot submit without the email confirmation--that doesn't exist--. Help?
Hi Emily - I've just emailed your survey confirmation email - these are normally sent to the person listed as the primary contact, which I think was the issue in this case. For you and others with this issue - you can email email@example.com with your project name and ID and we can send a second copy of the survey confirmation (or pilot credit registration email is that is missing).
I was under the impression that the Primary Contact should be the same person as the Owner. If that's not required, and the Project Admin (me, usually) can be the Primary Contact, I will try to update that for my other projects to simplify this process.
I've been trying to find examples of monitoring plans that have been done for other projects. Any suggestions or tips on what to include? I see that it is described here, but I would like to know if it's just a matter of the Owner signing off on the requirements described here or what else might be needed. For example, what is to be done with any dead or injured birds that might be found?
You do not have to follow one specific kind of format, however simply signing off on the credit requirements will not suffice. It should be a separate, written document that covers a period of 3 years and includes:
- methods to identify and document locations of the building where repeated bird strikes occur,
- the number of collisions,
- the date,
- the approximate time (if known),
- features that may be contributing to collisions, and
- a process for corrective action.
You can see the full list of submittals at the bottom of the credit's page: http://www.usgbc.org/node/1732698?return=/pilotcredits
Monitoring actions should occur twice a week at minimum. "Monitoring" means routinely walking the building perimeter before normal business hours or at night (it is recommended that it be done prior to 8 or 9 am, and daily during peak migration seasons), and geotagging or photographing the dead/injured birds. The plan will monitor the effectiveness of the building design in preventing collisions, and for EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems. projects, is the baseline for the measures implemented during the performance period.
These websites have more information on developing a monitoring plan:
How is the Hazardous Glass Area (HGA) calculated for each material? Is a material with a higher threat factor weighted the same as a material with a lower threat factor? And do you include the total material area from zone 1 and zone 2, or just 1 or 2?
When I review the Material Threat Factors for the different glazing options, I do not see tinted glass listed anywhere. Am I blind? Or am is it considered the same as clear glass?
We are still finalizing the glass selections for the project I am working on, but the majority of the façade is curtainwall made up of four different tinted glazing types.
Thanks in advance.
Tinted glass is not listed in the Threat Factor table. The experts that developed this pilot credit generally do not recommend tinted glass. However, tinted plexi and plexi that reflects ~80% scored about a 40. After speaking with them, they recommend that you use a threat factor of 40 for the tinted glass on your project.
Thanks, Theresa. Very helpful!
If a building is on a sloped site, and therefore the building height varies from one facade to the next, how shall the building height be determined relative to the BCTF spreadsheet?
In this kind of situation, you should measure 3 floors from the highest elevation point where the facade meets ground level. So for example, if the North facade is at an elevation of 150' and the South facade is set at an elevation of 135', you should measure up from 150'.
Hi, I was wondering how to calculate operable shutters that cover clear glass. Do I count this total area as a threat factor of 10 or do I add this on top of the threat factor area of 100 I am counting? As the shutters are usually open, exposing the clear glass, the area is generally a threat factor of 100, but when the shutters are occasionally closed, the threat factor diminishes to 10. I don't want to add the total facade area incorrectly but also don't want to incorrectly calculate the threat factor. Thank you!
When the shutters are closed, do they totally obscure the glass? If that's possible, then shutters that completely cover glass would score zero, as long as they are kept closed during peak migration (presumably there could be a more sophisticated operating scheme, especially if the project is doing post-construction monitoring). Either way, you wouldn't add the two threat factor values together (10 + 100).
Thank you Theresa,
Yes the shutters completely obscure the glass.
Thank you, I'll score them 0.
Maybe I am overlooking this, but I am having difficulty determining the zones for my building. I have a one-story building that has a building footprintBuilding footprint is the area on a project site used by the building structure, defined by the perimeter of the building plan. Parking lots, parking garages, landscapes, and other nonbuilding facilities are not included in the building footprint. with many re-entrant corners and undulating roof lines. There is a fair amount of clear glass, and I am indicating it all as 'Hazardous Glass Area'. Which facades do I consider Zone 1 or Zone 2 for the calculations?
I have the same question. Did you receive a reply with clarification, Miranda?
I would like to clarify, if i can attempt this pilot credits within the SSc category instead of the IOc? The IOc has limitations in terms of the number of points you can attempt.
thanks and more power.
Alfred, all pilot credits are earned through IDc1 or IOc1, and subject to the point limitations there.
Hi Tristan, thanks for the confirmation.
I am having difficulty determining if my project can comply with this credit. There is an inconsistency between the wording of the credit narrative and the results calculated in the BCTR spreadsheet and clarification on which calculation is intended would be helpful.
The narrative states (page 2, paragraph 2):
No more than 15% of the glazed area in Façade Zone 1 can have a Threat Factor higher than 75.
I interpret this to mean that if I have 100sf of glazing, no more than 15sf of that glazing can have a Threat Factor higher than 75. However, in the spreadsheet’s calculation of Z1 HGF (line 17) it is dividing the HGA by the total Z1 material area, not just the glazed area.
In my project, I have 1,476sf of glass and all of it has a Threat Factor of 100. Therefore, if I interpret the narrative literally the number I should get from the spreadsheet for the Z1 HGF is 100% (hazardous glazing area / glazed area). Instead, the spreadsheet reports 4.4% (hazardous glazing area / total Z1 material area). Should the narrative actually read:
No more than 15% of the material area in Façade Zone 1 can have a Threat Factor higher than 75?
Or, is the narrative correct and it’s the spreadsheet that requires revisions?
Also in the spreadsheet, the calculations are broken if one’s building has zero Zone 2 area. It’s not clear to me what the intended weighting is behind multiplying Z1 x2 and dividing (Z1x2)+Z2 by three. So does this formula need to change for buildings of three floors or less? Or does Z1 x 2/3 give the desired BCTR?
Also, for purposes of credit documentation, how does one define ‘story’ and ‘building height’ in the spreadsheet? My project has only one floor but a portion of it is a 50’ high maintenance bayA bay is a component of a standard, rectilinear building design. It is the open area defined by a building element such as columns or a window. Typically, there are multiple identical bays in succession.. Also, the building has three distinct parapet heights – is the credit interested in the tallest height? All of them?
Hi Joe - I came across the same issue. It appears that there are TWO requirements related to the building facade.
1. No more than 15% of the glazed area in Facade Zone 1 can have a Threat Factor higher than 75. This is noted as "Hazardous Glass Area" in the provided spreadsheet. I'm not sure if the provided spreadsheet calculates this requirement correctly. I will provide my own calculations.
2. Achieve a maximum total building Bird Collision Threat Rating (BCTR) of 15 or less. This calculation includes glazed and opaque surfaces. Once again, the provided spreadsheet has some errors. I will provide my own calculations.
Hope this helps!
We are a state natural resources agency with lots of bird strikes, so we would like to pursue this credit as part of our LEED EB: O&M project. It is not clear from reading through the credit whether EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems. requires a threat potential assessment, which is required for the new construction rating systems. EBOM clearly requires the facade monitoring plan, but does not mention the threat potential assessment. Thank you.
Hi Lee Ann,
It appears that the BD+C version of the credit has been posted here under EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems.. Regardless, the EBOM version currently does not require a threat potential assessment. It only requires that the project comply with the Facade Monitoring Plan requirements, one of the Interior Lighting options, and one of the Exterior Lighting options. This means that the project would need to develop and implement a building facade monitoring plan, as well as a lighting design strategy for interior and exterior lighting that meets the requirements. Hope this clarifies things.
Thanks for your help.
We're attempting this pilot credit on a hospital here in San Francisco, California. I have some thoughts about the building facade requirements that I'm curious if anyone has also encountered.
1. Adjacent buildings
My project is in a dense city. On one side, we have some houses very close to the property line that our building abuts. One house is 2' from my building and another is about 20' away. In calculating the various facade areas, I'm proposing to exclude the region blocked by the house that's 2' away, because no bird could possibly hit it there. However, I'm including the area of the facade eclipsed by the house 20' away ... because I that's enough distance for a worst-case bird to swoop in, turn sharply and smack the building.
I'm curious if others have encountered this issue. I think the credit language should offer guidance in these situations.
2. Sloping sites
My project site slopes one story in height from one side to the other. In dividing the facade into facade zones 1 and 2, I'm using a goofy-looking sloped region matching the site slope. It cuts through individual windows and made more work out of calculating the areas of various materials. No big deal, but a nuisance.
Is there a better way? Should the credit language provide a method for sloping sites?
3. Sensitive sites & bird magnets
San Francisco has adopted a bird-safety ordinance that our design is in compliance with. One feature of it that the pilot credit omits is an understanding that some project sites are more sensitive than others. Buildings near migration corridors, water, dense tree canopies, open space or other sanctuaries, for example, are held to a higher standard than buildings in less bird-ful places. In my mind, this is omission a significant flaw in the pilot credit.
4. Damaging to urban context?
Finally, I'm finding that the requirement to limit clear glazing (i.e., Threat Factor > 75) in facade zone 1 to just 15% of the glazed area in that zone is profoundly inappropriate for an urban building. My project isn't especially glassy, but our percentage is > 80% ... and yet we're in compliance with the City's bird safety ordinance because it's in an area devoid of bird-attracting features. I feel that, if we start building facilities with virtually no clear glazing, we'll trend toward cities of milky, opaque fritted facades and blank walls with little engagement with the street. Retail and food service projects will avoid this credit, as it would destroy their business.
Am I off base here? Anyone else finding the 15% rule problematic?
I see from the EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems. flow-chart that there is a performance period of three years in addition facade monitoring plan establishment. Am I interpreting this correctly?
I am not sure why the flow chart refers to the facade monitoring period as a performance period, as ongoing actual sustainable performance is not required for initial certification, with the exception of the lighting requirements. The facade monitoring period is a time to identify and document locations of the building where repeated bird strikes occur, the number of collisions, the date, the approximate time (if known), and features that may be contributing to collisions. A monitoring plan must be outlined for initial certification. Any necessary corrective facade measures would then be implemented during the performance period for recertification, which is the entire period between the initial certification and the recertification application.
The flow chart shown here was provided by USGBC. i can't comment on why it says that. Quite possible it is an oversight or error... after all these are pilot credits.
We will clarify the text under "Performance" in this EBOMEBOM is an acronym for Existing Buildings: Operations & Maintenance, one of the LEED 2009 rating systems. flow chart. As stated above, it should reflect the 3 year implementation of the monitoring plan rather than a 3 year performance period. Thanks!
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?
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.
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-eLow-E or Low-Emissivity Coating: Very thin metallic coating on glass or plastic window glazing that reduces heat loss and heat gain through the window; the coating emits less radiant energy (heat radiation), which makes it, in effect, reflective to that heat. In that way it boosts a window's R-value and reduces its U-factor. glass )
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.
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.
Technical Director, LEED
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