THE ARTS | Reshaping ideas, expressing identity
22 February 2008
Architects Look to Nature and Each Other
Energy and ecology encourage bold new solutions
The basic look and shape of American houses and business places haven't changed much for a long time. Now, however, energy and environmental challenges are encouraging new building materials, new ways to design buildings, and new respect for nature.
Multitasking Materials
Construction materials can do more than just holding up a building up and looking pretty. Like their human employers, construction materials are multitasking.
Still years away from marketing, SmartWrap is designed as a building material that can provide not only shelter, but also climate control, lighting, and power. The very thin material is made from the same plastic used to make soda bottles and is processed into rolls, according to the architectural firm that created it, KieranTimberlake Associates LLP.
The polyester film substrate layer is strong enough for protection from wind and rain -- it can reportedly withstand a Category 3 hurricane. To control climate, a layer of film is embedded with microcapsules of change-phase materials, which absorb heat in higher temperatures and release heat in lower temperatures.
For lighting, SmartWrap uses organic light-emitting diode (LED) technology -- organic molecules deposited onto the plastic film that emit light when an electric current is applied. Power comes from sunlight, absorbed by organic photovoltaic cells embedded in the film and converted into energy.
Some day, lightbulbs could be history. Incandescent bulbs, the kind Thomas Edison invented, convert only 5 percent of energy to light and release the rest as heat. Fluorescent bulbs are maybe four times more efficient, but even better choices are coming.
Biomimetics
How would Mother Nature design a building?
Through 4 billion years of evolution, organisms have come up with some neat designs. Architects are beginning to look to nature for clues to building sustainability.
Perhaps most famous among biologically informed buildings is the Eastgate shopping center and office building in Harare, Zimbabwe. The design was inspired by African termite mounds, where termites maintain a constant temperature of 87 degrees (to preserve a fungus that they cultivate to eat) by opening and closing flues that vent hot air.
The concrete Eastgate building has no air-conditioning system. During the night, big fans draw cool outside air up through spaces between the building's floors. During the day, smaller fans drive the warmer outside air through the same spaces, where the cool concrete moderates the temperature. As the air warms, it rises through 48 round brick funnels and out the roof. Fresh air circulates through the building twice an hour during the day. The building reportedly uses only 10 percent of the energy that a conventional building of the same size would use.
How about building materials inspired by nature? Architects and engineers are looking at the almost indestructible conch shell.
A conch grows itself by assembling bits of calcium carbonate into sheets and layers. It adds each new bit at a right angle to the finished bit. In this construction, a crack has a tough time getting anywhere, the force of any blow dissipated sheet to sheet and layer to layer.
For adaptation to changing temperatures, consider the flexible pinecone. Shut tight in the cold, pinecones open their scales to release their seeds when temperatures warm up. Researchers are looking for materials that change shape depending on the level of moisture in the air, opening to shunt warm moist air outside and closing to prevent warm moist air from getting inside.
Green Roofs
Actually, green roofs are not new. Plantings on top of buildings are at least as old as the Hanging Gardens of Babylon.
In recent decades, green roofs, which are vegetated roof covers for which plants take the place of materials such as shingles or tiles, have become somewhat common in parts of Europe, but for most of the world they are a new part of the landscape.
More use of green roofs could mitigate some problems for modern cities. They reduce storm-water runoff. They filter pollutants out of rainwater. Green roofs reduce energy use. Buildings with green roofs require less heating in the winter and less cooling in the summer than buildings with conventional roofs. In mass numbers they have the potential to reduce the urban-heat-island effect of entire cities.
Some U.S. cities are promoting the use of green roofs as a matter of policy. Chicago's City Hall has one. The American Society of Landscape Architects (ASLA) retrofitted its headquarters in Washington, D.C., with a green roof; the group says that from July 2006 to May 2007, "the green roof prevented 27,500 gallons of storm water -- nearly 75 percent of all precipitation on the roof -- from flowing into Washington, D.C.'s overburdened sewer and storm-water system. ... ASLA's green roof lowered air temperature by as much as 32 degrees in the summer when compared to a neighboring tarred roof."
Green roofs require strong structural support to carry a heavy load from a storm. They use wedding-cake layers of waterproofing membranes and root barriers to prevent leaks.
They come in different depths. Extensive green roofs use just a few inches of growing medium, typically expandable slate or clay mixed with a little compost; they are planted with alpine plants such as sedums. Intensive green roofs use deep soil and irrigation systems to grow grasses, shrubs, even trees.
These are excerpts from an article published in the eJournalUSA, THE NEXT NEW THING.
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