According to the u.S. Forest Service, planting fifty million shade trees in strategic, energy- saving locations could eliminate the need for seven 100-megawatt power plants. That’s a lot of megawatts – and a lot of trees.
Bringing that number down to a more realistic level for your homestead, consider this: Planting as few as three properly positioned trees in your yard can help cut your energy costs from 15 to 35 percent annually – adding up to thousands of dollars you’ll save on air-conditioning costs as the trees grow to provide abundant shade.
Trees create two cooling effects. First, they cool the air by absorbing water through their roots and evaporating it through leaf pores. This process – called evapotranspiration – can result in reducing peak summer temperatures in the surrounding areas by two to nine degrees.
Second, trees provide shade to reduce the solar radiation that heats your home. Shaded exterior walls may be nine to 36 degrees cooler than unshaded ones, lowering the need for air conditioning. These cooler surface temperatures also reduce the amount of heat in the surrounding air.
What (and where) to plant
Planting the right tree in the right place is the most important step in landscaping for energy conservation. Selecting trees that will effectively shade your home requires consideration of the size, shape and density of the trees, as well as the location of the moving shadows that the trees will cast.
In fact, according to the U.S. Department of Energy, a six- to eight-foot deciduous tree planted near your home will begin shading your windows during the first year. And, depending on the tree species and the style of your home, you can expect that tree to begin shading your roof in five to 10 years.
Here are some guidelines for planting trees to help reduce solar heat gain on your home and cut your cooling costs.
- Locate deciduous trees – ones that drop their leaves in the fall – on the east and west sides of your home. In the winter, the sunshine will flow through the trees’ bare branches to warm the house and windows.
- Plant deciduous trees with high, spreading crowns – such as oak, linden and walnut – to provide maximum summertime roof shading.
- Position shade trees or shrubs to shade your air-conditioning compressor; operating in the shade, the unit will use 10 percent less energy than one in the sun. (Note: Be careful to allow enough space for adequate airflow on all sides of the compressor.)
- Use dense evergreen trees or shrubs to provide continuous shade.
- Select tree species with lower crowns to provide shade from lower afternoon sun angles.
- Consider planting some slow-growing varieties of trees. Although slow-growing trees may require many years of growth before they will adequately shade your roof, they often have deeper roots and stronger branches, making them more drought-resistant and less prone to breakage.
- Shade your driveway, patios and sidewalks with trees, shrubs, hedges and climbing vines. Otherwise, these areas will act as large passive solar collectors, retaining heat and radiating it into your yard and home – even after the sun goes down.
Other benefits of trees
While you’re enjoying a nice, cool home and lower energy bills during the summer, you also can enjoy many other benefits that trees provide.
- Trees give off oxygen. One large tree can provide a day’s oxygen for up to four people.
- Trees clean the air. Trees absorb carbon dioxide and remove other common pollutants from the air, including nitrogen oxides, sulfur oxides, particulate matter and ground-level ozone.
- Trees attract birds and other wildlife. Increased tree cover brings these natural elements into communities, enhancing the quality of life for residents.
- Trees improve water quality. Trees reduce storm water runoff and erosion, and they remove harmful chemicals from the soil to prevent them from running into streams and rivers.
- Trees increase property values. The sale price of a landscaped home is, on average, between five and 20 percent higher than a home without landscaping.
- Trees add beauty and enjoyment to your physical surroundings. They create a positive psychological impact on peoples’ moods and emotions.\
- Trees create a calming effect. In laboratory research, visual exposure to settings with trees produced significant recovery from stress within five minutes. Studies also show that hospital patients recover more quickly in rooms that offer a view of trees.
- Trees control noise pollution. Strategically placed belts of trees can help reduce traffic and other neighborhood noises.
Trees build stronger neighborhoods and help reduce crime. Trees increase relaxation, reduce aggression and bring neighbors outdoors – creating additional interaction among neighbors and lowering crime activity.