Want to save money on your energy bill without investing in expensive retrofits and renova-tions? Get a shovel. Strategically planting trees and shrubs around your home is a tried-and-true way to save during warm weather when the air-conditioning runs many hours a day.
Solar heat absorbed through your home’s windows and roof increases your cooling costs, but – depending on the location and orientation of the trees and your house – you can gain signifi-cant energy savings by planting shade trees. In summer, a tree’s shade can cool surrounding air temperatures by as much as 9 degrees, and air temperatures directly under trees can be as much as 25 degrees cooler. This means that if your home currently is unshaded, you could be able to cut summer air-conditioning costs by 15 to 50 percent.
For areas where sunlight can come in through windows for natural warmth in the winter, choose deciduous trees (ones that lose their leaves in the fall) with high, spreading crowns to provide maximum shading during summer. Trees with crowns lower to the ground are more appropriate on the west side of your home, where shade is needed from lower afternoon sun angles.
Although a slow-growing shade tree may require many years of growth before it shades your roof, it generally will live longer than a fast-growing tree. Also, because slow-growing trees often have deeper roots and stronger branches, they’re less prone to breakage by windstorms or heavy snow loads. Slow-growing trees also can be more drought resistant than fast-growing trees.
Plant trees far enough away from your home so that when they mature, their root systems won’t contact the foundation – and branches can’t damage the roof. Also make sure trees won’t grow into your electric co-op’s power lines – and that branches damaged during a storm can’t fall into the lines.
A 6- to 8-foot deciduous tree planted near your home will begin shading windows the first year. Depending on the species and your home’s design, the tree should start shading the roof in 5 to 10 years.
Also consider shorter trees, shrubs and groundcover plants to shade the ground and pavement around the home, reducing heat radiation and cooling the air before it reaches your home's walls and windows. Use a large bush or row of shrubs to shade a sidewalk or driveway, plant a hedge to shade a sidewalk and build a trellis for climbing vines to shade a patio.
In addition, shading the coils of your outdoor air-conditioning unit or heat pump has the po-tential to modestly reduce energy demand. But if done improperly, there could be a net in-crease in energy use. Researchers from the Florida Solar Energy Center found that effective shading of an air-conditioning unit could yield energy savings of 6 percent, but an improper setup could result in a drop in efficiency of up to 15 percent. This drop in efficiency happens when vegetation blocks proper airflow to the unit or traps too much heat near it.
Plan about 3 feet of clearance – or whatever the manufacturer of the equipment recommends. Also be sure to frequently check the size of plants near the unit, because during the growing season the plants can creep closer to the system and interfere with proper air circulation.
For details on using shade trees to save energy, check the U.S. Department of Energy’s Ener-gy Efficiency and Renewable Energy website; go to its Energy Savers Landscape page at http://energy.gov/public-services/homes/landscaping. You’ll also find information about plant-ing windbreaks and landscaping for water conservation.
Plant the right tree in the right place
With a little research, careful planning and a simple layout, you can produce a landscape that will cool your home in summer and tame winter winds. Your well-planned yard should contain trees that grow well in the soil and moisture of your neighborhood, be properly placed to avoid collisions with power lines and buildings and increase your property’s value.
According to the Arbor Day Foundation (www.arborday.org), a proper landscaping plan takes each tree into consideration:
• Height. Will the tree bump into anything when it’s fully grown?
• Canopy spread. How wide will the tree grow?
• Is the tree deciduous? Will it lose its leaves in the winter?
• Form or shape. A columnar tree will grow in less space. Round, oval and V-shaped species provide the most shade.
• Growth rate. How long will it take for your tree to reach its full height? Slow-growing species typically live longer than fast-growing species.
• Soil, sun and moisture requirements. Try to avoid choosing species that require extra care.
• Fruit. No one wants messy droppings on busy sidewalks.
• Hardiness Zone. Check with your community's tree board, forestry department or a lo-cal county cooperative extension agent for a list of trees suitable for planting in your specific area. You also can go to www.arborday.org to look up your Hardiness Zone; most of Iowa falls into Zone 5.
Be sure to consider the final shape of the tree
The character of tree crowns and the form or shape of trees varies among species as much as leaf shapes or bark patterns. Shape is a good clue as to how well a tree will fit the space you have available, what problems might occur and how well it will help meet the goals you have for your property.
For more information
Arbor Day Foundation
Locate information about planting and growing trees, shop online for landscaping trees and shrubs or join the organization to get 10 free trees with your membership.
Iowa State University Extension
Find out about trees native to Iowa, research soil conditions and learn how to establish and maintain a healthy lawn.