Technically speaking, the smart facade -- or building envelope that adapts to environmental conditions -- dates back to the first window. But the contemporary idea of the smart facade has only been around for a few short decades, helped along by recent advances in chemical and material science. And over the past three years, we've seen the category boom.
Below, check out some of the most interesting building facades to come across the screen in recent years: From a thermal metal screen that curls up when it's hot, to a titanium dioxide-covered wall that scrubs the air of pollutants.
An Energy-Producing Algae Facade
This 200sqm wall, unveiled in Germany earlier this year, is the result of three years of testing by a group of designers from Splitterwerk Architects and Arup. Its vibrant chartreuse hue isn't just an aesthetic flourish -- in fact, it's tinted by millions of microscopic algae plants, which are being fed nutrients and oxygen to spur biomass production. Facilitated by direct sunlight, the speedily growing little cells end up heating the water, and that heat is harvested by the system and stored for use in the building.
"It is a test for the technology, but it also represents a huge step forward," said Jan Wurm, Arup's Europe Research Leader. "If we can demonstrate that microalgae biofaçades can become a viable new source of sustainable energy production, we can transform the urban environment."
A Light-Responsive Facade That "Breathes"
This pair of Abu Dhabi towers are sheathed in a thin skin of glass -- fashionable, but not ideal for the desert climate. So the architects at Aedas designed a special, secondary sun screen that deflects some of the glare without permanently blocking the views. Thanks to a series of faceted fibreglass rosettes -- based on traditional Islamic mashrabiya -- which open and close in response to the temperature of the facade.
"At night they will all fold, so they will all close, so you'll see more of the facade," Aedas director Peter Oborn told The National. "It's using an old technique in a modern way, which also responds to the aspiration of the emirate to take a leadership role in the area of sustainability."
A Facade That Eats Smog
Back in 2011, the chemical company Alcoa unveiled a remarkable technology that could clean the air around it. The material contained titanium dioxide, which effectively "scrubbed" the air of toxins by releasing spongy free radicals that could eliminate pollutants. The stuff has made appearances on streets, clothing and architecture since then -- most recently, on the sun screen of a new Mexico City hospital, the Torre de Especialidades.
The hospital is cloaked in a 90m long skin of Prosolve370e tiles, developed by a German firm called Elegant Embellishments. The technology is based on the same process: As air filters around the sponge-shaped structures, UV-light-activated free radicals destroy any existing pollutants, leaving the air cleaner for the patients inside. According to Fast Company, even the shape of the sun screen is significant: It creates turbulence and slows down air flow around the building, while scattering the UV light needed to activate the chemical reaction.
A Low-Tech, Operable Skin
In Melbourne, Sean Godsell Architects sheathed RMIT's design school in thousands of small, sandblasted glass circles -- each affixed to a central rod. Based on humidity and temperature inside the building, these rods pivot automatically to facilitate (or block) the flow of air through the facade. A simple but clever solution.
A Metal Mesh That Reacts to Heat
Sung's research deals with biomimetics, or how architecture can mimic the human body. This sun shade was made with thermobimetal -- a material that's actually a laminate of two different metals, each with its own thermal expansion coefficient. That means that each side reacts differently to sunlight, expanding and contracting at different rates -- causing tension between the two surfaces, and ultimately, a curling effect. So when the surface gets hot, the thin panels on the shade curl up to allow more air to pass through to the space below -- and when it cools down, it closes up again.
There are hundreds of other examples out there, so comment below if we've missed a really interesting one.