My parents’ yard has many trees and their air conditioner seems to run less than ours. Can you give me some tips on where and what kinds of trees to plant?
The U.S. Department of Energy has done sophisticated computer models showing that properly placed mature trees can cut your utility bills by up to $250 a year in a temperate climate.
However, many factors about a house affect the utility bills, with landscaping being just one of them. Older people, such as your parents, tend to feel colder, so they often don’t set their air conditioner thermostat as low as a younger family with children. The type and efficiency of the central air conditioner also impact how much electricity it uses.
There are many other benefits from landscaping with the proper type and placement of trees. By shading your house, the walls, shingles, and even curtains will last longer because the sun’s damaging ultraviolet rays are blocked. The air immediately around your home will be less polluted and the oxygen level will be higher from the plants’ photosynthesis. Trees also create a sound barrier from road noise, and the rustling of leaves in a breeze can be relaxing.
People often think of shading the house as the primary cooling effect, but trees also function as natural air conditioners through a process called evapotranspiration. As the tree roots draw water from the ground, the leaves give off this water in the form of water vapor, cooling the air like our own perspiration cools our skin.
The air temperature near the house on a well-landscaped yard can be 10 degrees cooler than on a treeless one. A smaller temperature difference between indoors and outdoors reduces the heat gain through the walls and thus reduces the load on the central air conditioner. Also, by keeping the air around the air conditioner outdoor unit cooler, its efficiency is increased.
The key to efficient landscaping with trees is selecting the proper species and placing them in the proper location for your specific climate. A well-landscaped efficient yard in the hot, dry Southwest will look totally different from one in Kentucky.
First, draw a layout of your yard and decide where you want to add trees to landscape for your type of climate. Also determine the height, shape, and type (evergreen or deciduous) of the mature trees and their growth rates. Next, talk with a local garden store expert to make sure you are planting trees that will thrive in your climate zone.
In temperate and northern climates, you will also be concerned about winter heating bills. In these regions, you want the warm winter sun to shine on your house and in your windows for free passive solar heating. This is best accomplished by planting deciduous trees on south, east, and west sides, leaving a small gap to the southwest for summer breezes. During winter with the leaves gone, much of the sun will shine through. Since the sun never shines from the north during the winter, plant evergreens on the north side for a winter windbreak.
In a hot, humid climate, you use air conditioning more often. Natural breezes can be somewhat helpful during the evening, but because they tend to be overly humid, it is not as helpful as in temperate climates. Shading by placing tall trees to the south side is most important. Avoid an overabundance of plantings, particularly near the house, because they will raise the humidity level without the cooling effect.
Write for Utility Bills Update 438, showing landscaping diagrams and a selector guide of 100 trees. Include $3.00, a business-size SASE, and Update number. Mail requests and questions to James Dulley, Kentucky Living, 6906 Royalgreen Drive, Cincinnati, OH 45244. Go to www.dulley.com to instantly download.