Keep Your Big Windows — and Save Birds Too
One of the consistent criticisms of the modern houses I often write about is that their large windows are bad for birds. Deaths of birds striking glass buildings is in the range of 100 million to 1 billion a year in the United States alone, so it is definitely a problem that needs to be addressed. Thankfully, groups like the Audubon Society are spreading the news about the concern, and many architects are starting to address the problem through their designs for exterior walls.
Much of the attention on bird strikes is given to high-rises, relative to the paths of migratory birds, but most of the deaths happen (during the day, at least) within a much narrower expanse of just 50 feet above the ground. This points to the importance of addressing the problem in single-family houses, too — particularly modern ones where glass is used generously to provide views from the inside to outside.
Bird strikes happen primarily for three reasons:
Glass is reflective, particularly at oblique angles, blending the panes into their surroundings.Multiple panes of glass (parallel, as in bridges, or perpendicular, as at corners) give the impression of disappearing by being transparent.Illuminated interiors attract migrating birds flying at night, especially at tall heights.This ideabook presents some tactics for mitigating the above through architectural means — meaning the focus is on elements that are an integral part of a building, rather than additions like curtains and furnishings. The tactics are specifically aimed at the first two causes of bird strikes, since designs responding to those should mitigate No. 3, and because much of the concern with the last has to do with urban areas at particular times of the year, rather than with houses year-round.
Before we get into specific tactics, it's worth pointing out what is considered the ideal in modern architecture: full-height glass walls. Yet this specific house is actually a good example of what can be done to eliminate bird strikes, for the house can transform from this ...
... to this. Operable screens on the exterior transform the glass walls from reflective panes to patterned panels that filter the sunlight and, in the process, deter bird strikes. This is a solution that depends on those elements being closed, but the rest of the ideabook looks at permanent, fixed solutions.
Learn From Bird Blinds
The most obvious lessons can be drawn by looking at bird blinds: structures that exist to allow people to watch birds in their habitats.
As this example shows, the ideal opening is a small one, where the amount of solid area is greater than the open or window area. That works for bathrooms and other rooms where windows can be small, but what about the living rooms and other spaces where owners still want larger pieces of glass for light and views?
Know Your Property
It's best to approach a house's design relative to the site. This is a general rule, but in the case of mitigating bird strikes, it's helpful to consider trees and, if known, the paths of birds across the site. This house, by Travis Price, presents a predominantly solid wall by the entrance, which happens to be the most open part of the site.
But on the back of the house, where the glass is more expansive, the trees are denser, fairly close to the glass. Having trees near windows obscures reflections on the glass, reducing the likelihood of bird strikes.
Sunshades
Providing a fixed screen in front of the glass walls is a good solution for eliminating the reflectivity of the glass while still allowing views, albeit of a more filtered variety. Wood slats like these also cut down on the heat gain of direct sunlight, thereby serving two purposes.
More decorative approaches are possible, especially with computer numerically controlled (CNC) routers that allow much artistic freedom. In this case views are forsaken in favor of cutting down on sunlight, protecting birds in the process.
Fritted Glass
A similar effect can be achieved through ceramic frits — silk-screened patterns fired onto the glass, typically the inner layer of an insulated unit.
Different Types of Glass
This house has translucent channel glass incorporated into its front elevation, while still allowing views through narrow vision-glass panes on the side and clerestories above.
This bridge has translucent glass to eliminate the views that happen with two parallel panes of glass. Note the strip of clear glass that occurs at eye level, allowing views out from the bridge.
Screens
While insect screens are not as architecturally permanent as other solutions and they are found only at operable windows, I can't resist this retractable insect screen that can cover large expanses. I could see it being used as a bird screen even when the sliding wall is closed.
Create a Buffer
Incorporating a space between the glass wall and the exterior is a good way to eliminate reflections, while also creating a transitional zone that bridges the realm of the house and that beyond. The metal grille on this porch ensures that birds will not fly into the glass walls beyond.
Here is another house with a grille layered over an in-between space. In the foreground are some slats just in front of a glass wall, but the area of concern is in the distance, where the slats extend up to the second floor.
From inside we can see the full-height glass wall that is set behind the wood slats and the covered outdoor space. This is a case where cutting down on direct sunlight and saving birds also creates an enjoyable space.
Overhead Planes
For some people the views are the raison d'être of modern houses. So while most of the previous suggestions affect the views of the surroundings, these last few suggestions help to preserve views. The first is overhead planes. When they're deep enough, overhead planes — be they sunshades, roof extensions or trellises — over window expanses can obscure reflections on the glass.
Angled Glass
Angling the glass walls so they reflect the ground or sky, rather than the immediate surroundings, is another means of retaining views, if a fairly impractical one. Nevertheless, the home shown here is a good example of a situation that works, given the fairly substantial angle.
For this to work, the angle needs to be more than just a few degrees. This photo from inside shows how the view is oriented to the water via the angle.
Bird-Safe Glass
Not yet widespread but offering great potential is Ornilux bird-safe glass created by Arnold Glas in Germany. The glass has a special layer that reflects a UV spectrum that birds can see but people cannot. The technology is based on spider webs, whose silk works in a similar way to keep birds from flying through them and destroying them.
From a distance Ornilux looks completely transparent, but up close we can see the pattern visible to birds. Even if the glass reflects the surroundings, it mixes with the "noise" of the pattern to discourage the birds from flying into it.
