Landscaping for energy conservation

Tuesday, March 3, 2015

When it comes to planning their landscape, some gardening enthusiasts are thinking only about the colors, textures and overall look they want to achieve.

However, a well-planned landscape also can have a direct impact on your energy bills, said David Hillock, Oklahoma State University Cooperative Extension consumer horticulturist.

“One reason to plant trees and shrubs around the house that may not immediately come to mind is energy conservation. Well-placed trees and shrubs can help reduce heating and cooling costs,” Hillock said. “A few things to consider when planning your landscape are the angle of the sun, orientation of the house and direction of winter and summer winds.”

Anyone who has lived through an Oklahoma summer knows the heat can be brutal. Providing shade can significantly reduce the heat flow into a home, which in turn can help reduce your energy bills.

Hillock said recent studies suggest shade can reduce heat flow by as much as two-thirds. Likewise, shading roofs with tall, high-branching trees such as oaks, can help with cooling.

“While summer shade is desired to reduce cooling expenses, we also want to maximize winter sun,” he said. “To get the best of both worlds requires careful tree selection. Shade is good in the summer but can block the warming rays of the sun in the winter months.”

Characteristics to look for include high branches to block summer sun, but permit winter sun, which strikes the house at a much lower angle. Open branching, such as that of the Kentucky coffeetree, allows for a more open winter canopy and allows greater winter sun penetration.

Homeowners also may want to consider the timing of leaf drop. Ideally, look for trees that drop leaves between Oct. 15 and Nov. 15.

“When it comes to selecting trees that will be close to your house, homeowners may want to avoid trees with cone-shaped crowns, such as pin oaks and many evergreens because they provide significantly less shade in summer and block winter sunlight,” Hillock said. “Consider shading south and west facing walls, which capture a great deal of heat from the hot afternoon sun during those dog days of summer.”

Wind is another contingency when planning an energy conserving landscape. Your home can lose much more heat on cold, windy days than on cold, calm days. Well-placed trees and shrubs can intercept winter winds and reduce heat loss.

“I know there are days when it seems the wind is blowing from every direction at one time, but typically the coldest winds arrive from the north and northwest,” he said. “Therefore, a windbreak is best located along the north and west edge of your property.”

Foundation plantings are the plant materials placed along the perimeter of the home and impact the energy gain and loss from a home in a variety of ways. They act as insulation against wind, reducing air currents close to the home. They also create pockets of air that act to insulate the home. As with wind breaks, evergreens have a greater impact on energy savings than deciduous plants.

For more information regarding energy conservation and the landscape, check out OSU Fact Sheet HLA-6417: Landscaping for Energy Conservation at http://osufacts.okstate.edu.