Suggested date of release:
after October 17, 1999
Claudia Chandler (916) 654-4989
Media and Public Communications Office
(Third article in the 3-part series for October)
Landscaping -the Natural Way to Save Energy
Autumn is one of the best times of the year to plant trees, shrubs and vines around your house. Winter rains water them gently and naturally, and colder weather helps lessen the shock of transplanting. By the time summer's heat rolls around again, the plants are well established.
Landscaping can truly beautify your home. But by planting carefully and thoughtfully, you can improve your privacy, raise the value of your property, add to your home's comfort and - this may surprise you - cut your energy bills.
Planting the correct trees, shrubs, vines and groundcover can make your home both warmer in the winter and cooler in the summer. In fact, according to figures from the California Energy Commission, the right type of tree can reduce your summer cooling costs by 20 to 40 percent!
Anyone who has ever stood in the sun on a hot day will appreciate the value of shade. But in the heat of summer, plants can keep your home cool in other ways besides offering shade: they create a cool microclimate that can dramatically reduce the temperature in the surrounding area by as much as nine degrees. During photosynthesis, large amounts of water vapor escape through their leaves, cooling the passing air. The generally dark, coarse leaves also absorb solar radiation.
Deciduous trees - trees that drop their leaves each winter - offer one of the best ways to cut home cooling costs. If you plant them on the northeast-to-southeast and northwest-to-southwest sides of your house, they can provide excellent protection from the summer sun by shading roof, walls and windows.
They also help to warm the house in cold weather. Because they lose their leaves in autumn, deciduous trees permit winter sunlight to reach the house, helping to heat it with solar energy.
This benefit is why experts suggest that, if you live in a moderate or cool climate, you don't plant deciduous trees directly to the south of your house. In the winter, even the bare branches of mature deciduous trees can reduce the amount of sun reaching your house.
When you're picking out a shade tree to plant, consider its height, growth rate, branch spread and shape. Those factors will influence the cooling benefits the tree offers. For western exposures, wide-spreading trees are best. And don't forget to consider the height of the tree - ones that never grow tall won't provide much shade.
In general, try to shade as much of the roof and walls of your home as possible. If you need to choose between covering a small portion with dense shade, or a larger area with less dense shade, go for the larger area. That strategy will produce the best cooling results in summer.
It's also a good idea to plant trees so they shade the windows that allow summertime heat to enter your house. If you're concerned about preserving your view, keep the sun's path in mind and plant one or two smaller trees slightly to the side of the window.
In addition to trees, vines and climbing plants also act as effective sunscreens. They are particularly good against south-facing walls where you probably don't want shade trees. Planting a deciduous vine such as grape lets you enjoy the benefits of both summer shade and winter sun.
Keep air circulation in mind when you're planting vines. By setting trellises away from the wall, you allow air to circulate. Placing vegetation too close to your house can trap summer heat and make the air around your house even warmer. Leaving space behind trellises also helps to prevent vines from attaching themselves to your home's exterior and damaging it.
Consider the prevailing wind and air currents, as well, when you're planting, Evergreen trees that don't drop their leaves can offer valuable protection from the winter winds that chill your home. If you plant them where they can block a cold wind before it hits the outside of your house, they will help to cut your heating bills.
Just as evergreens can stop winter winds, carefully placed trees and shrubs will direct cooling summer breezes to your home. Bushes planted a few feet away from the house will provide extra shade without obstructing cool air currents. Shrubbery will also reduce soil and wall temperatures and help to protect your home's foundation from root damage.
Don't overlook the benefits of planting low ground cover such as grass, small plants and bushes. A lawn is usually 10 degrees cooler than bare ground in the summer. Large paved areas and gravel beds will store heat, especially if they're dark in color. In addition to causing substantial temperature increases, they reflect glare. You can reduce this problem by surrounding areas like your patio or driveway with shrubs and grass. Better yet, consider drought-resistant ground covers that use less water.
As you figure out the best places to plant this autumn, keep these final suggestions in mind. Throughout the year, the sun's position changes. In the summer, it appears high in the sky. It is more intense and shines for more of the day than it does in the winter, when the sun is closer to the horizon. Be aware of seasonal sunshine patterns as you select planting sites.
Be sure your sites are safe, both above and below the ground. Check for underground and overhead utilities or other obstructions. Avoid planting trees directly under utility lines. If you need to dig, particularly at a streetside location, contact your local utility company. They can help to identify potential underground obstructions.
For best results, talk to knowledgeable salespeople at your local nursery or garden center. They can direct you to native plants that survive in your area with minimal care and that require little water. They'll be able to point out aspects of a tree or shrub that may not be immediately apparent, such as how tall and far-reaching it will grow. Whatever plants you choose, make sure they can withstand local weather extremes.
Landscaping isn't an alternative to weatherizing your home, but it is an effective, additional way to help lower your heating and cooling costs. That's why many utility companies offer landscaping rebates or support local tree-planting programs. Check with yours - maybe you qualify for such a program.
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This article is based on the California Energy Commission's Home Energy Guide, to be published early in 2000.
You can find additional information about energy in California on the Energy Commission's Web Site at www.energy.ca.gov.
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