What a Difference a Tree Makes

Planted in the right spot, a tree can insulate your home, trim your energy costs and help cut back your contribution to global warming

04-01-2005 // Heidi Ridgley

RANJIT BABRA marvels at the stately, 80-year-old hickory tree towering above him in the northeast corner of his Bethesda, Maryland, backyard, but there’s one thing he’d like to change: its location. Had it been planted on the west or south side of the house, the tree would have done more to shield his house from the summer sun and the winter wind, reducing his energy use, his utility bills—and his contribution to global warming.

“Deciduous trees like this hickory are ideal for energy-efficient landscaping,” says Babra, a horticulturist for Washington, D.C.’s Urban Forestry Administration. “In summer, the shade provided by the canopy of a strategically placed tree can reduce air conditioning use by up to 50 percent. In fall when it loses its leaves the sun can warm the house.”

But that’s not a reason to overlook evergreens, says Jeffrey Langholz, an environmental policy analyst at the Monterey Institute of International Studies in California. Planted in a row on the north or northwest side of a home, these trees will work like linebackers in winter to block the cold—another way to keep the thermostat from inching upward and a coal-fired power plant from emitting more greenhouse gases.

Of course, one person planting a single tree won’t prevent the polar ice caps from melting, says Greg McPherson, director of the U.S. Forest Service Center for Urban Forest Research at the University of California–Davis. “But,” he says, “if everyone planted just one tree in a location that keeps the air conditioning from doing double time, the reduction in emissions at power plants would be substantial."

Research is also suggesting that larger trees provide the greatest cost-saving benefits. “Trees, such as oaks, are more expensive to maintain than smaller trees because you probably can’t prune them yourself,” McPherson says. “But because a larger tree can reduce energy bills by as much as $200 a year, we’re finding that the savings outweigh the expenses.”

Regardless of the tree’s size and location, Babra cites many other benefits that come from having any size native tree in the yard. “One of them is aesthetics—sheer beauty,” he says, noting how dogwoods enliven Washington every spring with their showy pink or white blossoms. In fact, healthy trees can increase property value by an average of 10 percent, according to U.S. Forest Service statistics. An average-size tree also soaks up about 50 pounds worth of carbon dioxide a year. This isn’t much considering an average car spews about 10,000 pounds a year, “but in the collective,” says McPherson, “it’s something.”

As for Babra’s hickory, it might not be perfectly positioned, but its leaves are still manufacturing oxygen and filtering harmful, health-threatening pollutants from the air, while its roots prevent soil erosion and absorb stormwater runoff that—instead of gushing untreated into the nearby Potomac River—recharges the groundwater supply. “In a different spot, this tree could benefit the environment even more,” says Babra. “But it’s still doing a lot right where it is.”

Heidi Ridgley is an associate editor.

Made for Shade
An average-size tree planted close to your home can cool your home as much as one window air conditioner. The best native shade trees, recommended by the U.S. Forest Service Center for Urban Forest Research at the University of California–Davis, include:

Ash
Basswood
Hackberry
Locust
Maple
Oak

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