Sustainable buildings inspired by nature

The landmark Roman Catholic cathedral by architect Antoni Gaudi has been a work in progress since 1882. Gaudi, whose style was heavily influenced by the natural world, was not a fan of the straight line. His magnificent structure features double twist columns that support the roof and draw the eye up to the stained glass skylights, which illuminate the sacred space with gold and green light.

Gaudi's work recalls the sun-dappled light that filters through a forest canopy. Visitors to the nave, the central area of the church, may feel like they're walking through a forest glade. His columns, which branch out to support the vault and roof, mimic the way trees distribute weight and as such are able to bear a greater load than traditional columns.

This office and shopping complex was Africa's first building to use passive ventilation. Built in the mid-1990s, it takes advantage of consistent daily temperature swings to cool and heat naturally. Fans draw in fresh air at ground level and push it up through hollow floors and vents to the roof, where warm air escapes. Thick brick walls, limited windows, shades and a pale facade keep things cool.

Pearce was inspired by the termite mounds that dot Zimbabwe's savannah. These huge structures, some as high as 9 meters (about 30 feet), are shaped to catch the breeze at the base and vent hot air out the top. Termites, which need to keep their body temperature at around 30 degrees Celsius (86 Fahrenheit), are constantly building new tunnels and blocking others to regulate heat and humidity.

This iconic skyscraper has been a part of the London skyline since 2003. Designed by Norman Foster and more commonly known as The Gherkin, it also benefits from passive heating and cooling, along with a double-skin glass facade that helps insulate the offices and maximize natural light.

The building's interior is open and spacious thanks to an exterior lattice structure. Diagonal braces provide support for the 180-meter (590-foot) tower — much in the same way a silica skeleton helps this glass sponge survive the ocean depths in the Pacific and Indian oceans. The Gherkin's ventilation system was also based on the way the sponge filters seawater for nutrients.

A five-story apartment complex in northern Germany, built in 2013, has integrated living matter into its design. A " bioreactor facade" helps to provide shade and provides a form of renewable energy to power the building. Two south-facing sides of the building are mounted with 129 bioreactors, glass panels that form a vertical algae farm.

The algae — which enjoy a steady diet of liquid nutrients and carbon dioxide — bask in the rays of the sun and use photosynthesis to grow and fill the panels. They're harvested and stored in tanks in the building, then fermented at a nearby power plant and used to generate electricity. During the summer, the algae help shade the windows; slower growth in the winter provides more light.

Spanish architect Santiago Calatrava's addition to Milwaukee's premier art gallery, completed in 2001, is shaped like the prow of a ship — appropriate for its lakeside location. A massive sunscreen roof, composed of 72 steel fins, can open and close to provide shade. When fully extended, it has a wingspan of 217 feet (about 66 meters), comparable to a 747 jet.

Calatrava wanted to reflect the urban and natural features of the setting, especially the passing boats and sails. The wings of the 90-ton roof take 3 1/2 minutes to open or close. The graceful movement is reminiscent of a bird taking flight.

Hundreds of millions of birds die each year running into transparent windows. Stickers attached to the glass can help but need to cover a large part of the surface — birds are used to flying through tight spaces. German company Arnold Glas has developed an insulating glass sheeting with a special ultraviolet reflective coating, nearly invisible to humans, that helps steer birds away from danger.

Most birds, like other animals, are able to see light in the ultraviolet spectrum because they have more rods and cones in their eyes than humans. It helps them to differentiate and avoid leaves as they fly through the treetops. And many spiders make their webs from silk that reflects UV light. It helps them attract insects — but sends birds flying in the other direction.

In the early 1990s, researchers at Japanese tile manufacturer Inax developed a silica coating that can be painted on exterior wall tiles to help keep them clean. Silica, a natural element found in soil, forms microscopic bumps on the tiled surface. Moisture in the air sticks to these bumps and attracts particles of soot, exhaust and other pollutants. When it rains, the buildings are washed clean.

The researchers came up with the idea from observing snail shells, which have their own pattern of tiny bumps. The uneven surface creates tiny pools of water on the snail's shell, and contaminants float on these pools and are eventually flushed away by the next shower.