Energy Efficient Landscaping

Energy efficient landscaping can reduce home utility bills by as much as 30 percent.


| October/November 1994



146 energy efficient landscaping - painting

Not only can it lower your utility bills, energy efficient landscaping can raise your property values.


ILLUSTRATION: MOTHER EARTH NEWS STAFF

The United States has 42 million acres of yard (an area about the size of New England). Most of these yards waste water, are sprayed with chemicals, don't use native plants, and can't support wildlife. Only a small percentage take advantage of their natural ability to shield a house from the elements. According to the U.S. Department of Energy, a recent U.S. Forest Service report, and numerous university studies, energy efficient landscaping can substantially reduce a home's utility bills. By how much? Between $300 and $750 a year according to those same studies, and that doesn't even include the increased value that low utility bills and a well-designed landscape add to home resale prices (15% according to a survey by the National Gardening Association).  

Tempering the Sun

The strategy for handling the sun is simple: block it when it's hot, let it in when it's cold. What's more complicated is where to place and not place plantings to achieve those goals. In many cases, removing trees can be even more important than planting them.

As landscape writer Robert Kourik noted, "The old-fashioned idea that an energy-conserving landscape means a thicket of deciduous trees along the southern side of a house [so the leaves will block the sun in the summer, but drop off and let the sun in during the winter] is not only ineffective, but often counterproductive." For most of the country, heating costs more than cooling, so a home's southern exposure should usually be cleared to let in the sun's warmth. Even leafless deciduous trees can block 25-60% of the sun's energy.

Tall shade trees should be placed on the eastern and western sides of the house. Because the summer sun rises high in the sky, it's the roof and the eastern and western walls that get direct heat and thus need the most protection. If you don't have established plants to the east and west, put fast-growing deciduous vines on a trellis along a wall. This will give almost immediate cooling benefits while you wait for larger, slower-growing trees to mature.

To determine where to plant eastern and western shade trees for the most effective sun control, you need to know the path of the sun at your home's location. Charts from the local library will give "your" sun's position in the sky for different seasons and times of day. By knowing the sun's position, you know exactly where to place your plants to maximize summer cooling without interfering with needed winter warmth.

In Columbus, Ohio, for example, the midday summer sun is 73 degrees high in the sky. From the southwestern to the southeastern corner of a Columbus home, trees should be planted along a line that veers off at a 73-degree angle of due south. The fan-shaped area facing south in between those "lines" should be free of large shade-producing trees. This will ensure maximum warmth during the winter while blocking the hottest summer sun. If you do need to plant trees or shrubs to the south and don't want to block the sun, knowing the winter sun's position tells you how far from the house you need to plant.





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