This paper was first offered at GPD 2023.
Link to the complete GPD 2023 convention ebook:
Authors: Wim Stevels, Julia Schimmelpenningh, Matthias Haller
Abstract
Birds colliding with glass on buildings are a worldwide concern. Several hundred million birds are killed on account of collisions with glass in buildings. Collisions happen each in long run habitats and through migration by flying into glass home windows, hyperlink bridges, and curtain partitions that mirror the open sky and vegetation. As transparency in façades remains to be very a lot valued in reference to human wellbeing, decreased lighting necessities and as an aesthetic factor, a number of technical developments have taken place to include bird-deterrent components into glazing options. In some circumstances, these bird-deterrent components are interfering with photo voltaic or low-e glass coatings wanted to make sure the efficiency of the glazing. In addition, some bird-deterrent options might have an effect on design intent or person expertise. In this contribution, PVB interlayers for extremely efficient and low-surface protection bird-friendly laminated security glass shall be described. In explicit, it is going to be proven how these might be mixed with typical glass coatings with out lack of efficiency for e.g. photo voltaic issue or U-value, whereas effectiveness as a hen deterrent answer is maintained.
Introduction
Birds colliding with glass in buildings is a worldwide concern. Collisions occur primarily due to two completely different conditions:
1. Birds mistake the reflections on the glass of the vegetation or environment as actual (reflection misperception)
2. Birds fail to acknowledge clear glass in any respect (transmission misperception)
The two eventualities are depicted in Figure 1. Although for people inside buildings the notion of glass in transmission is dominant, mirrored photographs are extra frequent for birds.
Many cities and nations worldwide are placing laws in place that mandate new buildings to incorporate bird-friendly glass. As transparency in façades remains to be very a lot valued in reference to human wellbeing, decreased lightning necessities and as aesthetic factor a number of technical developments have taken place to include bird-deterrent components into glazing options. Techniques which were used are based mostly on e.g. etched glass, fritted glass, glass with coated UV-markers, and most lately interlayers.
To perceive trade-offs in glass design with bird-friendly glazing higher, you will need to perceive how the effectiveness of hen deterrent glazing options are examined and rated. In each Europe and the US, the effectiveness of glazing options is examined utilizing (flight) tunnel testing. Bird tunnel testing for glazing merchandise is a non-injurious, standardized binomial selection method that makes use of wild songbirds to find out the relative effectiveness of patterns at deterring hen collisions. Previously captured, wild migrating songbirds are launched in a flight tunnel and have the choice to ‘exit’ by flying both in direction of a take a look at glazing or unmarked management glass, seen on the far finish of a darkish, enclosed area.
Both the take a look at pattern and unmarked management glass are protected by nets, in order that no birds are injured within the dedication of the effectiveness. The effectiveness is outlined by the variety of birds that fly in direction of the take a look at glazing, divided by the entire variety of hen releases. Of course, the latter ought to be sufficiently massive to derive significant outcomes. More particulars are supplied in one of many subsequent sections. In Europe, suggestions are based mostly on the Collabs/ Biological Station Hohenau-Ringelsdorf classification scheme (equal to the ONR 191040 classification scheme for nonreflective, see-through conditions), which designates solely these markings as extremely efficient (“category A” in Figure 2) that obtain an total results of not more than 10 % of directional flights in direction of the take a look at pane [1].
In the US, the American Bird Society calls the effectiveness the “threat factor” and defines hen pleasant glazing as having a menace issue of 30 or much less [2]. Solutions with a menace issue of 15 or decrease could also be eligible for a LEED® pilot credit score on this inexperienced building score program. An overview of the effectiveness of hen deterrence glazing and the completely different classification is supplied in Figure 2.
A standard design technique in hen pleasant glazing is the appliance of patterns (e.g. stripes, dots) in or on the glass which can be seen to birds in transmission, disrupting look of e.g. clear skies or vegetation that could be seen behind within the glass. In reflection, this can be much less apparent because the reflectivity of glass will depend on the viewing angle, the character of the glass and different glazing components, akin to glass coatings, which may by extremely reflective in nature. It ought to be famous that at broad angles, which gives the very best reflection, the chance of collision is smaller than at nearorthogonal flight approaches. The protection space of the sample utilized is a key variable in a hen deterrent answer.
There are doubtlessly many different variables past the protection share alone that may decide the effectiveness as a hen deterrent answer, such because the sample itself, the position of the sample in/on the glazing, the transparency, the colour or distinction, and reflectivity of the sample. All these components present for a continued want for product testing. However, because the major operate of glazing is to offer daylight for human building occupants, and to offer strains of sight out and in of a building, patterns that cowl a big space of the glass floor are typically not fascinating. This identifies space protection and effectiveness as typical main design trade-offs in hen pleasant glazing design.
Another limitation in hen pleasant glazing design is the massive selection in glazing configurations that may be manufactured and are used, relative to the variety of tunnel exams that may be executed in an affordable period of time. There are just a few acknowledged take a look at amenities worldwide on the time of writing. Testing is proscribed to the precise migration season of the songbirds and lots of hen releases are wanted to ascertain effectiveness in a significant method. This signifies that solely a fraction of precise configurations put in might be examined in that very same configuration, even barring measurement and framing results.
Therefore, in lots of circumstances, one is proscribed to e.g. a coating or frit print from a provider, utilized on a particular glass from that provider, doubtlessly together with practical coatings from the identical provider wanted for the complete efficiency for the glazing. So relatively than an “add-on choice”, the bird-friendly glass design turns into a bundle selection the place the thermal and photo voltaic efficiency necessities of the building, the daylight and viewing wants of building occupants, the architectural design intent and the effectiveness for birds all have to be mixed. This might be fairly difficult if all the individual glazing factor decisions are restricted by examined configurations for effectiveness by way of hen deterrence.
A possible answer could be to evaluate configurations based mostly on particular traits, akin to seen gentle transmission and visual gentle reflectance, which can be in between examined configurations with the identical sample. Such an method is helped by the truth that most birds (tetrachromatic imaginative and prescient) have wider spectral sensitivity than people (trichromatic imaginative and prescient). Mapping of configurations by their optical traits additionally allows dialogue with the ornithologists executing the tunnel testing. Many phrases and components which can be effectively outlined and significant for people working within the glass business, akin to clear glass, laminated glass, low-e coating and photo voltaic management coating, have little which means to these working exterior the business. In flip, in fact, most individuals targeted on glass and glass merchandise may have restricted understanding of hen imaginative and prescient and the intricacies of tunnel and different types of hen testing.
This contribution will present a high-level mapping of present approaches to bird-friendly glazing by way of effectiveness and protection space. Furthermore, it is going to be demonstrated how for a particular bird-deterrent answer, mapping of glazing properties has allowed extending tunnel take a look at outcomes and rankings to a spread of glass parts, enabling typical glass design to be mixed with hen safety.
Mapping of present options
To be capable to position varied bird-deterrent glazing options, varied applied sciences had been mapped with reference to share coated space and share approaches. As the supply on this market phase has been quickly rising in recent years, this may solely be a snapshot in time, and the information shouldn’t be construed as complete or present on the time of publication. To execute this work, third social gathering knowledge as revealed had been taken into consideration, assuming these had been collected in good religion, with out an choice of impartial verification of their reliability. Test knowledge from each the US and Europe had been considered, regardless of variations in methodology. The outcomes are supplied in Figure 3.
In the interpretation of Figure 3, you will need to understand {that a} low % of approaches (menace issue), is fascinating, as is – generically talking – a low protection space. These options are grouped within the decrease half of the graph. The space marked with the blue dotted strains is the world the place a extremely efficient score is obtained together with a protection share of lower than 1 %. All method ranges are decrease than the minimal threshold set by the American Bird Society as “bird friendly” (menace issue 30) [2] or the brink set in New York City Local Law 15, 2020 (menace issue 25). Most would even qualify for the brink for a LEED Pilot Credit on this inexperienced building score program.
However, fairly a couple of options fail to achieve a extremely efficient score within the European methodology [1] now mandated in native laws in e.g. Germany. There is a really restricted variety of options which can be rated as extremely efficient and have protection areas under 5 %, and solely laminated sequin options obtain a excessive efficient score at lower than 1 % protection space. It ought to be famous that for fritted options, strengthening of the glass is a concurrent impact which impacts not solely the mechanical properties and breakage sample, but in addition the choices for post-production processing (must be minimize to measurement prior) and visible look (e.g. curler wave/anisotropy). For the case examine on this publication, a particular laminated sample (“laminated sequins”) was reviewed.
Tunnel testing
The description of the tunnel testing has been adopted from reference [3]. A tunnel take a look at experiment examines the directional selections of birds flying in direction of a marked and unmarked pane by means of a 7.5 m lengthy flight tunnel, which is mechanically pivoted and might be manually positioned to comply with the position of the solar. Thus, symmetrical gentle incidence on the take a look at panes is ensured always, see Figure 4. The left and proper half of the top of the tunnel are occupied by two completely different panes: an unmarked float glass reference pane on the one facet and the take a look at pane on the opposite, as in Figure 5.
The birds used within the exams are wild birds from the ringing program of the Biological Station Hohenau – Ringelsdorf, Austria and subsequently individually identifiable. This ensures that no hen is used for a take a look at flight greater than as soon as per calendar day. The daylight-adapted take a look at birds are placed in a begin tube by means of the tunnel wall on the rear finish of the tunnel, and instantly fly from the darkish in direction of the open entrance finish. A mist web generally used to catch birds for ringing is placed 40 cm in entrance of the take a look at panes.
The web’s thread thickness of 0.1 mm falls under the birds’ frontal visible acuity and is subsequently not perceived. The birds are gently caught and protected against influence with the take a look at panes and are instantly launched after flight. The take a look at flights are recorded from behind with a video digital camera. A ceiling, facet partitions and {a partially} translucent curtain create a weak-lit cabin behind the take a look at panes. The trapezoidal sheet assist prevents birds from seeing the sky and vegetation apart from as reflections within the take a look at space. The synthetic backdrop consists of a white canvas in entrance of a camouflage web. To create lifelike reflections, a darkened chamber measuring approx. 170 x 170 x 170 cm is mounted behind the take a look at space, creating lighting circumstances that correspond to the inside of buildings.
These lighting circumstances are managed with measuring devices. Test pane and reference pane are mounted at an angle of 125° to the flight path of the birds. Similar to the facet mirrors of a automobile, the panes create reflective photographs of the encircling habitat within the birds’ visible axis as they fly by means of the tunnel. Since the tunnel is pivoted to comply with the motion of the solar, the take a look at and reference panes are all the time frontally lit. Depending on the sunshine circumstances (solar, clouds, overcast sky), kind of contrasting reflections of the environment happen on the panes, and constructions of the chamber building behind the panes turn into kind of seen, accordingly.
The surrounding vegetation is homogeneous, guaranteeing that reflections in each panes are as comparable as doable. The birds’ flight axis is parallel to the incidence of daylight, with the solar all the time coming from behind. The panes don’t obtain any direct daylight. After each three individual exams, the put in take a look at panes are modified. The sequence of various take a look at candidates and the positions of the respective take a look at and reference panes are randomized. The flights and selection conduct within the individual exams are recorded by video digital camera, damaged down into flight sequences, and managed and evaluated in gradual movement.
A case examine for extra versatile glass design
Base product description
The laminated sequin hen deterrent answer studied right here is Saflex® FlySafe™ 3D. Saflex® FlySafe™ 3D PVB is a 0.76 mm interlayer with utilized 3D-sequins. The sequins are seen for birds and people and have a unique coloration entrance to again. The sequins are reflective silver on the entrance, as seen from the outside, and black on the again (inside) in order to not obscure views or diminish visible high quality from the within. The sequins include 9 mm diameter spherical markers, organized in a grid with a distance of 90 mm from sequin middle to middle. This grid corresponds to an total protection space of 0.8%.
For use in a laminate, a masking layer of clear 0.76 mm or thicker Saflex® PVB interlayer should be placed on the silver facet of the sequins involved with the glass. A typical laminate configuration might be seen in Figure 6. The image in Figure 6 demonstrates to some extent that the reflective sequins do not need a uniform mirror-like look, however relatively a seemingly three-dimensional floor construction, which leads to delicate twinkles relying on the angle of method.
Evaluated programs
Three glass configurations had been evaluated in underneath the flight tunnel take a look at protocol described beforehand:
- 44.4 laminate utilizing typical clear glass and a Saflex® FlySafe™ 3D interlayer together with Saflex® Clear 0.76 mm cowl layer in entrance of the sequins (Configuration 1; 44.4 Saflex® FlySafe™ 3D)
- 44.4|16|4 insulated glazing unit: entrance pane laminated coated glass laminate utilizing typical clear glass and a Saflex® FlySafe™ 3D interlayer together with Saflex® Clear 0.76 mm cowl layer in entrance of the sequins with a sturdy, low-e coating in position #4, a 16 mm air area, and a mm clear glass again pane (Configuration 2, 44.4 Saflex® FlySafe™ 3D_c#4|16|4)
- 46.6c#4 coated glass laminate utilizing typical clear glass and a Saflex® FlySafe™ 3D interlayer together with Saflex® Clear 0.76 mm cowl layer in entrance of the sequins with a sturdy, impartial photo voltaic management coating in position #4 (Configuration 3; 46.4 Saflex® FlySafe™ 3D_c#4)
The photo voltaic and visual traits of those two configurations are listed in Table 1 beside.
It was verified that the variations within the values are attributable to the presence of the coating because the distinction in glass thickness is simply too small to have a fabric impact. The coated programs have the next reflectance, leading to a step clever improve of mirrored gentle (8, 12 and 19% respectively) in addition to a stepwise lower of total seen gentle transmission (88, 80 and 65% respectively)
All three programs had been examined within the flight tunnel take a look at beforehand described and resulted in lower than 10% of approaches (menace issue) and in consequence had been rated as extremely efficient [3, 5]. It does present that the distinctive Saflex® FlySafe™ 3D look and grid is efficient in decreasing hen approaches within the tunnel take a look at, even with the extra reflective, decrease transmission coated programs. This is outstanding because the testing protocol was executed targeted on effectiveness in reflection. To be capable to apply the flight tunnel take a look at to a wider array of glazing components, a lot of potential variations had been mapped by modelling.
Clear glass
The seen gentle properties of 51 completely different float glasses of ten completely different float glass producers for thicknesses of 4, 6 and 10 mm with completely different iron content material had been evaluated. All merchandise examined had a visual gentle transmission between 92 and 87% and a light-weight reflection of 8 or 9%. Given the vary of seen gentle properties of the three examined Saflex® FlySafe™ 3D configurations and the ensuing “highly effective” score, it was accepted that the supply of the float glass was not a fabric issue within the consequence of the tunnel take a look at. Clear glasses from completely different suppliers can be utilized for the meeting of Saflex® FlySafe™ 3D configurations with no want for re-testing, offering no different glazing components are current that have an effect on seen gentle properties in a fabric method.
Laminated glass
The seen gentle properties of 5 completely different laminates (xx.4 with x both 4, 5, 6, 8 or 10 mm glass) based mostly on typical clear float glasses had been evaluated. All merchandise examined had a visual gentle transmission between 88 and 84% and a light-weight reflection of 8%. Given the vary of seen gentle properties of the three examined Saflex® FlySafe™ 3D configurations and the ensuing “highly effective” score, it was accepted that the thickness of the laminate was not a fabric issue within the consequence of the tunnel take a look at inside the evaluated boundaries.
Low-e coated glass in IGU’s
As an method to mannequin and evaluation efficiency insulated glazing models (IGU’s), it was first mapped how the properties of basic low-e glasses differ by gentle transmission and light-weight reflection. In order to cowl a variety, knowledge for 180 low-e coated glasses from ten completely different suppliers had been compiled. Besides provider, glass kind (low/mid-iron), glass thickness (4, 6, and eight mm) and coating kind (sometimes 2-3 varieties per provider, however as much as 8 varieties) had been different variables. As glass thickness turned out to not be a key variable, the outcomes are proven in Figure 7 for 4 mm glass.
It ought to be famous that Figure 7 accommodates many overlapping datapoints, as each properties are supplied with rounded numbers. Two teams of coating are readily recognized: a bunch with larger reflectance (> 15% and decrease transmissions (LT-HR group, blue dots)); and a bunch with decrease reflectance and better transmissions (HT-LR group, orange dots). In order to evaluate the impact in lifelike configurations, probably the most excessive coated glasses in every group, marked with black bordered dots in Figure 7, had been taken as a foundation for IGU modelling. In this fashion, it may be assured that the complete vary of low-e coated choices is roofed within the IGU modelling, with out having to mannequin every potential variation in IGU composition.
As an instance of the method, for all 4 marked coatings in Figure 7, 4 several types of IGU’s had been modelled:
- A single laminated IGU with a low-e coating in position #5
- A double laminated IGU with a low-e coating in position #5
- A single laminated triple IGU with two low-e coatings in positions #4 and #7
- A double laminated triple IGU with two low-e coatings in positions #4 and #7
The outcomes are proven in Tables 2a and 2b.
Table values with a inexperienced background are inside the limits of examined configurations that may very well be rated as extremely efficient, respectively 65% for gentle transmission and 19% for gentle reflection. In the HT-LR group (Table 2a), all double IGU’s fall inside the examined vary. Even for the double coated triple IGU, the decrease reflection restrict coating is effectively inside the examined vary of properties, with potential to evaluation larger reflectance coatings. At the very restrict of this group by way of reflection, the transmission and reflections are nonetheless exterior the examined vary. In the LT-HR group (Table 2b), even when assembled in a single laminated IGU, the reflectance values improve over non-assembled coated glass, inflicting the upper reflection restrict coating to fall exterior the examined vary. Only the low-e coating with the bottom reflectivity within the HR group falls borderline inside the vary of examined configurations. For the double coated triple IGU’s, all configurations are exterior the examined vary for each transmission and reflection.
Mapping of photo voltaic management coated IGU’s The broad method as used for the low-e coatings is just not readily utilized to photo voltaic coloration coatings, as there’s a big range of coating applied sciences, efficiency traits and visual properties to select from. By design, many have decrease gentle transmission and coloured choices (e.g. gray, blue, inexperienced, and so on.) are additionally frequent. Often, there’s a extremely reflective or comparatively low reflection (“neutral”) variant to select from. For functions of this work, the present supply of impartial excessive transmission photo voltaic management choices in Europe was mapped by gentle transmission and reflection (to the surface).
No lower than 24 choices from 8 producers had been recognized in 6mm glass, as mapped in Figure 8. Most of the datapoints within the higher left nook are extra sturdy photo voltaic management coatings that can be utilized with out edge deletion, together with a restricted selectivity (seen gentle transmission over g-value). The marked datapoint (massive dot, black border) within the middle of factors on the suitable facet of the map was used for additional modelling, to evaluation if such a coating would nonetheless provide values which can be inside the vary of glazings examined within the flight tunnel exams. Double and triple laminated glazing models had been thought-about, in both the absence or presence of low e-coating within the again pane. The outcomes are proven in Table 3.
Table values with a inexperienced background are inside the limits of examined configurations that may very well be rated as extremely efficient, respectively 65% for gentle transmission and 19% for gentle reflection. The different configurations are shut, and by particular decisions for both the low-e coating, or the glass kind, or the precise photo voltaic management coating chosen a configuration may very well be chosen to have the general required glazing properties (U-value, g-value, gentle transmittance), whereas nonetheless staying with the examined boundaries for the laminated sequin bird-deterrent answer. As an illustration, the usage of low-iron glass relatively than typical float glass within the triple IGU will increase the sunshine transmission a couple of p.c, shifting it contained in the examined vary.
The big range of photo voltaic management coatings available does drive the query what property could be of most concern. At the restrict of sunshine transmission, birds are more likely to keep away from stable showing objects [6]. In that sense, the darker a glazing will get in transmission, the much less susceptible it’s to hen strikes. In addition, the distinction with the excessive reflective sequins solely will increase, doubtlessly making decrease gentle transmissions acceptable with out additional testing. In distinction, the extra reflective the coating used is, the decrease the distinction with the sequins turns into. Here future testing will nonetheless be invaluable to show any discount of effectiveness with reference to hen strikes for the laminated sequin answer. Use of coloration in glazing, be it derived from mass coloured glass, coatings, or interlayers sometimes reduces the sunshine transmission of the glazing, and in that sense has an influence impartial of the colour tone. Color layers in entrance of the laminated sequins ought to be prevented with out testing, as they cut back the mirrored distinction with the laminated sequins.
Conclusions
Sophisticated take a look at protocols are available to evaluate the effectiveness of glazing configurations with reference to their potential to keep away from hen collisions. However, given the big range of glazing choices, some extent of interpolation is required to match the glazing efficiency from a building: bodily facets, design side, occupant wants for daylight and look at, and bird-deterrence. Based on a technical market mapping, it may very well be proven {that a} laminated sequin answer is likely one of the most superior options available by way of each protection space and effectiveness. With some constraints, this answer can be utilized in a big selection of glazing configurations with properties inside the examined vary for this bird-deterrent answer, together with use in insulated glazed models, both within the absence or presence of low-e or photo voltaic management coatings. It is essential to confirm the traits of the ultimate undertaking configuration relative to examined configurations to evaluate if the effectiveness score might be maintained with out additional testing.
References
1) Rössler, M.; Doppler, W. Vogelanprall an Glasflächen, brochure Wiener Umweltanwaltschaft, 2019.
2) Sheppard, C.D. Evaluating the relative effectiveness of patters on glass as deterrent of hen collisions on glass in: Global Ecology and Conservation, e2019, (https://doi.org/10.1016/j.gecco.2019.e00795).
3) Rössler, M. Reduction of Bird-Window Strikes – analysis of SEEN glass components, 2020.
4) Eastman Chemical Company Product Technical Sheet Saflex® FlySafe™ 3D available from 2022.
5) Rössler, M. Vogelanprall an Glasflächen – Untersuchungen von Saflex® FlySafe™ 3D / SEEN shiny 9/90mm und Saflex® FlySafe™ 3D / SEEN matt 9/90mm, 2022.
6) Schmid, H.; Doppler, W.; Heynen, D.; Rössler, M. Vogelfreundliches Bauen mit Glas und Licht, ISBN 978-3-9523864-0-8, Schweizerische Vogelwarte Sempach, 2012.
