greening your landscape

mature deciduous trees provide shade in the summer


Jeffrey Lee Posted on: October 29, 2008

“In this time of tightening wallets and soaring energy bills, almost everyone has adopted some sustainable practices inside their homes. Americans also are incorporating techniques outdoors that help save energy or water, too, according to a national survey on sustainability.
Conducted online on behalf of the American Society of Landscape Architects (ASLA), the survey found that 96% of the 2,253 adults interviewed have adopted sustainable or energy-efficient practices around the home, such as turning off lights, installing energy-saving bulbs, or lowering the thermostat. But of those involved with or responsible for lawn and garden care, 58% also use techniques such as planting shade trees, harvesting rainwater, or recycling water for plants, to lower energy and water costs.”
While a gap remains between practices indoors and outdoors, that’s quickly changing. “Homeowners are becoming much more savvy to energy savings” from blocking solar heat gain or reducing water use, Tom Tavella, vice president of communications for ASLA, tells EcoHome. “It’s amazing how much that’s changed over the last five years.”

Tavella, who also is vice president and director of design in the Glastonbury, Conn., office of BSC Group, which provides landscape architecture and other services, recommends several ways architects, gardeners, and building professionals can use or modify landscaping to save energy and water. They include:

1. Employing Landscape Shading

It’s important that the home be oriented so that it can absorb heat from the sun during cold weather and reduce solar heat gain during warm weather, but Tavella adds that strategic landscaping can improve that effect. “On the eastern side, southeastern side, and south side, we plant deciduous trees 20 to 30 feet away from the building. That helps reduce solar gain during the summer months.”

In addition, deciduous trees are effective in mixed climates because they lose their leaves in winter time, allowing solar gain during the cold months, Tavella notes.

Employing shading and evapotranspiration, which is the process by which a plant actively moves and releases water vapor, can reduce surrounding air temperatures as much as 9 degrees, according to the U.S. Department of Energy’s Consumer’s Guide to Energy Efficiency and Renewable Energy. Because cool air settles near the ground, air temperatures directly under trees can be as much as 25 degrees cooler than air temperatures above nearby blacktop, the guide states.

2. Erecting Windbreaks

Windbreaks reduce heating costs considerably, according to the DOE and Tavella, and their benefits increase as trees and shrubs mature.

“On the northern edges, you want to plant windbreaks of evergreens to prevent cold winds coming from the north from hitting the house,” Tavella suggests.

3. Controlling Heat Island Effect

Pavement around the home can radiate heat and increase summer cooling loads, a process known as the “heat island effect.” Installing ground covers instead of pavement will reduce solar reflectivity and heat going into the home, Tavella says.

A large bush or row of shrubs can shade a patio or a driveway, the DOE advises, while a hedge can veil a sidewalk and a trellis for climbing vines can shield a patio area.

4. Utilizing Native Plants

Using native plants can conserve water, Tavella says, because they are adapted to the climate. And limiting turf areas minimizes the need for supplemental watering, according to the DOE. Homeowners also can reduce evaporation by using mulch and by watering or irrigating plants in the early morning when evaporation rates are low, the DOE adds.

For information about promoting water conservation in landscaped areas—called xeriscaping—visit the DOE or the National Association of Home Builders’ Research Center’s Toolbase Services.

For more on efficient landscape practices, check out Right as Rain.