Most people love trees, but few realize that a wind break (a row of trees that deflect the wind) or even a single shade tree can help you save energy, too.
How? A wind break helps to stabilize the temperature in your yard and your house in two ways. First, wind speed is reduced in winter, which keeps warm air inside your house. Second, shade trees in summer keep the house temperature lower, thereby lowering energy costs from air-conditioning and cooling.
The trick, however, is planting the right trees in the right places. Here are some tips on designing wind breaks to save energy, adapted in part from information provided by the Arbor Day Foundation. They report that summer electric bills can drop as much as 35% when wind breaks and shade trees are in the right place.
East Is East: Sun, Shade and Wind Breaks
Before you plant or remove any trees, determine which direction is east, south, west, and north. The sun rises in the east, travels across the southern sky, and sets in the west. Understanding this simple fact makes a huge difference in using trees on your property to save energy.
Because the sun crosses the southern sky, the south side of a building always receives the most sun and gets the warmest. The north side, by contrast, gets no direct sunlight and is always the coldest and shadiest. And while the east side gets morning light, the west side will, of course, get sunlight in the afternoon and at sunset.
If this all seems obvious to you, look around your neighborhood and you'll see that many people nonetheless plant evergreens on the south or west side of a house. While this keeps things cool in summer, it has the unwanted effect of making a house cold and dark during winter months, which causes heating bills to skyrocket.
The way around that problem is to avoid evergreens on the sunny sides of a building. Pruning or removing existing evergreen trees that block the sun will warm up a house in winter by using the sun's rays to heat the house.
Plus, planting deciduous shade trees on a building's sunny sides is smart: Shade trees keep the house cool in summer heat, and when these trees lose their leaves in autumn, the sun will come shining through to warm the house and lower heating bills.
Designing a Wind Break: Start Simple
Another important point is knowing which direction the prevailing winds in your area generally come from. In many places, the winds blow from one direction in winter, and another in summer. Plan your wind break accordingly. Finally, pay attention to overhead power lines and underground utilities before you start planting any trees.
Keep your wind break simple: the Arbor Day Foundation recommends planting a row or two of evergreens on the northern edges of your property. When placed there, the evergreens will let the sunshine on your house in winter while buffering any icy northern winds.
An L-shaped windbreak can protect houses from winds better than a straight line, so if, for example, your winter winds come from the north and east, plant evergreens on the north and east sides of your property. Just make sure they don't get too close to the house or block the eastern morning sun in your windows.
Of course, the taller the trees, the greater the wind protection. The Arbor Day Foundation recommends tall wind break evergreens like Canadian hemlock, Norway spruce, and American arborvitae.
Trees and Saving Energy: Summer Shade, Winter Sun
Some research has found that trees growing closer than 15 feet to a building can actually trap heat and increase cooling costs, so even on the north side, leave some room for airflow and breezes. Branches can also fall in storms, so keeping trees at a distance makes a lot of sense.
As stated above, deciduous shade trees that drop their leaves in fall are good choices on the east, south and west side of a building, as long as there's room for them to grow. Maples, London plane trees, hackberries, and oaks are just a few of the choices available.
You can also realize some energy savings by planting shade trees on the sunny side of air conditioning units, driveways, and patios. By shading an air conditioner, for example, customers can save an estimated 10% on cooling costs.
Trees provide value far beyond energy savings, of course. By beautifying our homes and neighborhoods, providing food and shelter for songbirds and other wildlife, and lowering energy costs, trees provide immense benefits. To find out what types of trees will benefit your home the most, check out the Arbor Day Foundation's Tree Calculator.