Next eco-house will utilize ‘green walls’

It started last year with four small sheds on a Clarksville farm.

With the help of a small grant from Green Roofs for Healthy Cities, environmental science and technology professor David Tilley started growing vines on the walls of small houses he built to observe their ability to conserve energy from water and sunlight.

Now, Tilley's research on green walls is making up a key design feature of WaterShed, the university's 2011 Solar Decathlon entry.

Sponsored by the U.S. Department of Energy, the biennial Solar Decathlon challenges 20 selected college teams worldwide to create state-of-the-art solar-powered houses that feature innovative energy-efficient designs. Construction on the 2011 entries is set to begin in January, and the houses will be displayed on the National Mall next October.

The university WaterShed team is entering the competition with some big shoes to fill. The university's previous entry, known as LEAFHouse, earned second place overall in the 2007 competition.

To ensure WaterShed gets the same rave reviews, Tilley and the rest of the university team — composed of about 300 faculty and students — are using his research to build an edible green wall on the west side of the house.

Tilley said the green wall will likely feature a vine that boasts edible fruits, such as a special type of grape or kiwi. The vines will be able to grow up the length of the house wall by wrapping around a metal trellis.

Tilley said the concept of green walls, which he discussed at Thursday's Water Resources Symposium in Stamp Student Union, has the potential to reduce resource consumption in houses and buildings by trapping natural rainwater and sunlight.

"Vegetation has the ability to capture and store small amounts of water in the canopy," he said.

By storing rainwater in its canopy of leaves, Tilley said the green walls of vines help to reduce the amount of water runoff from storms. In addition, the dense vegetation serves as a good barrier for filtering sunlight, reducing the thermal energy that penetrates building walls and helping to cut back on energy costs from air conditioning.

"By having more water and vegetation on the landscape, you'll have reduced consumption of energy for air conditioning," he said.

But Tilley said the largest role the green wall will play in WaterShed is to get people thinking of using collected water as a resource instead of wasting it.

"By bringing water right into the landscape of the house, it's there front and center," Tilley said. "We're treating it as a valuable resource and not something you want to get rid of."

Architecture professor and team leader Amy Gardner said the green wall will serve as a visible reminder that WaterShed is constructed to function as its own ecosystem by connecting the house with the earth.

"I think the connection between the house and the site will help WaterShed stand out against our competitors," Gardner said.

Tilley said he is confident the marketability of green walls will also help separate WaterShed from the other houses.

"We've been working on the idea of covering buildings with vegetation," Tilley said. "There's an emerging industry in North America for selling green walls for buildings."

Senior environmental science and technology major Ali Alaswadi — a WaterShed team member involved in Tilley's continued research on LEAFHouse — said the approachability of the green wall will make it an intriguing design for eco-conscious homeowners looking to update their houses.

"The systems can be replicated by any other user," Alaswadi said. "With the right vines, trellis and amount of sun, you should be able to put it on your home."

Gardner said the green wall will send the message to homeowners that they can use new eco-friendly designs sooner rather than later.

"We're showing people that we can do things now to houses that are already built that can change the way people live in them," she said.

saravia at umdbk dot com