Extension Communications
3614 Administrative Services Building
Ames, Iowa 50011-3614
(515) 294-9915
2/25/02
Contacts:
Chris Feeley, Foresty, (515) 294-6739, cfeeley@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the Week Beginning March 1, 2002
Landscaping For Energy Conservation
Chris Feeley
Program Specialist
Foresty
It is time to start planning your landscapes now before the planting season is in full swing. When planning your landscape, keep in mind that strategically planting trees and shrubs near buildings may be the best long-term investment for reducing home heating and cooling costs. The small initial cost of planting trees and shrubs provides a long-term investment that will continually reduce energy and fuel consumption. In addition, a well-designed landscape can add 7 percent to 15 percent to the resale value of your home.
Trees and shrubs reduce energy needs through shading and evapotranspiration (release of water vapor as plants adsorb heat). Groves of trees can replace or reduce the need for air conditioning. The air temperature below trees can be as much as 20 degrees cooler than air above nearby blacktop or exposed rooftops. Research conducted by the U.S. Department of Energy has shown that proper placement of trees and shrubs around buildings can reduce summer energy needs as much as 50 percent. In addition, planting windbreaks can reduce your winter heating cost by 10 percent in urban communities and up to 40 percent for farmsteads (see ISU publication "Farmstead Windbreaks: Planning," PM-1716).
So what is the catch? The catch is that trees and shrubs need to be carefully placed where they will benefit the home most by offering the maximum shade in the summer but minimum shade in the winter. The majority of unwanted heat in the summer comes from sunlight through windows. Statistics show that twice as much solar heat enters through the west-facing and east-facing windows. Therefore, planting shade trees on the west and east-side of the home should be of highest priority.
Select trees that will block the solar heat early in the morning and late in the afternoon, but will not block the light in the winter when sunlight is desired to warm the house. Deciduous shade trees, those that drop their leaves in autumn, work best to achieve this goal. The ideal shade tree should have a broad crown with dense foliage to offer the maximum benefit. Green and white ash, Kentucky coffeetree, sugar and black maple, red maple, American linden (basswood) and river birch are examples of trees that provide excellent shade in the summer and lose their leaves in the winter. Select trees that can be planted within 20-25 feet of windows and will grow at least 10 feet taller than the windows.
Since the sun is directly overhead in the summer, planting trees on the south side of your home will not save on your energy bill. This does not mean trees cannot be planted on the south side of the home, just select smaller trees that will not shade your home from the winter sun and plant them farther from the windows to prevent the undesirable shadows that may be cast on the home. Avoid planting trees that keep their leaves such as oaks and Norway maple, or trees that have dense branches like littleleaf lindens.
Last but not least, avoid planting fast growing weak-wooded species close to the house such as willow, cottonwood and sycamore. These trees are prone to splitting and are often considered "messy" based on seed production, amount of leaves and the number of branches that break.
By following these simple guidelines you can easily reduce your home's energy consumption, improve your home's aesthetics and increase the property value. What else can provide such a long-term financial return with a minimal startup cost? For more information download Iowa State University Forestry Extension Note F-375 at http://www.forestry.iastate.edu/ext/pubs/F-375.pdf.
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