Growth of rooftop plants defines 'green building'

11/3/2012 9:15 PM
By Associated Press

LEBANON, Conn. (AP) — Spread out in an isolated section of the 400-acre Pride's Corner Farms, a low-key $1 million-a-year operation brings the concept of "green" building to new heights — rooftops, to be specific.

Here on a rolling six acres, exposed to the elements inside low-slung plastic trays, sit drought- and weather-resistant plants such as sedum, chives, grasses and allium that are custom grown for green-roof projects around the country.

"They're really tough, tough plants," says Jim Costello, manager of the LiveRoof business at Pride's Corner, which is both a grower and regional distributor for the product.

The vegetation has to be tough, because plants used atop roofs are exposed to high wind, bitter cold and searing sun during the course of a typical year.

Costello credits horticulturist David McKenzie, now a project leader for the Michigan-based LiveRoof company, with developing many of the fundamentals of green-roof installation, including the use of a modular system of trays employed at Pride's Corner. It's a green trend that got a major boost after a series of deaths in Chicago during a terrible heat wave in the 1990s that killed 750 people and led Mayor Richard M. Daly to search for ways to reduce what was then known as the "urban heat island effect," caused by a concentration of too many surfaces that absorb heat, especially asphalt and cement.

But there's more to the story of green roofs than keeping down the number of deaths tied to urban hot zones. Green-roof systems also are touted for their ability to absorb water, reducing excessive runoff that can overwhelm city sewer and drainage systems, are said to improve air quality in cities and can double or even triple the life of a roof by protecting it from the elements.

But perhaps the most alluring element of a green roof is its ability to lower temperatures inside buildings by an average of 6 to 8 degrees, thereby cutting air-conditioning costs. The cost savings can amount to between 20 percent and 30 percent for many projects, according to some estimates, making green roofs viable for industrial and commercial uses, as well as in public buildings - especially those placed urban areas - but Pride's Corner is starting to see some interest among private homeowners as well.

One of Pride's Corner's most recent installations was at Public School 41 in New York City's Greenwich Village, where a 9,000-square-foot Green Roof Environmental Literacy Laboratory was completed just last month. The project — totaling $1.7 million, with the roof system alone costing about $450,000 installed — is expected to have a payback period of about six years, Costello says, because of lower air-conditioning costs.

"No edges of the modules are visible to disrupt the natural appearance of the green roof," says Jose Miranda, an associate with project architecture firm Murphy Burnham & Buttrick Architects in New York City, in a statement about the project. "Pre-vegetated modules are installed already dense with full-grown plants to create an instant green roof."

The average LiveRoof project is about 2,000 square feet and contains five to 10 different cultivars, so that if any one particular plant variety fails in a given environment other plantings will take over. Cuttings from the various cultivars are placed in trays of between 4 and 6 inches in depth containing a largely inorganic shale mixture that discourages weeds from sprouting up.

Pride's Corner's biggest project was 15,000 square feet at the airport in Burlington, Vt., and it also has produced a 10,000-square-foot LiveRoof for the University of Connecticut and a smaller building topper at Connecticut College's student center. Different-colored vegetation allows Pride's Corner to offer patterns and even company logos atop roofs, though these orders have not yet been seen at Pride's Corner.

The farm partners with several installers and arranges to truck the LiveRoof system in trays aboard tractor-trailers. The cost of a LiveRoof generally ranges between $22 and $32 a square foot. "Everything is all custom grown for a project," Costello says.

For Pride's Corner Farms, which sells millions of perennial plants, trees and shrubs to garden centers throughout the Northeast, the LiveRoof business represents only about 3 percent of annual sales, according to Costello. But he says the number has been growing at a rapid pace ever since the farm started its first LiveRoof project five years ago, and in a down economy that's a good thing.

What's more, it takes only one manager and about a half dozen hands to oversee the operation, which includes a four-acre crop of sedum that grows alongside the LiveRoof trays that are generally planted in the early spring and ready by the fall for installation. Costello said he is experimenting with planting later in the season this year to see if a LiveRoof can be nursed through the colder months.

Planting is relatively easy, involving spreading cuttings on top of the special shale mixture, adding fertilizer, watering and waiting for the plants to take root inside the trays. Trays have to be regularly weeded, but the shale mixture reduced the problem somewhat. Farm workers also occasionally have to move the rooted cuttings around to ensure an even spread throughout the trays.

"Once you install the trays on the roof, it looks like it's been there forever," Costello says.

The success of the LiveRoof business has encouraged Pride's Corner to go one step further and try out a new LiveWall "vertical garden" system that uses the same concept as LiveRoof for heavily walled urban areas in search of a little greenery. The concept, which will be unveiled in June, could allow people to grow a variety of flowers and herbs even in confined spaces.

"It would be great for a restaurant with an outdoor cafe," Costello says.


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