Landscape Design – Planning an Energy Efficient Landscape Part I
Energy efficient homes are ones that utilize efficiency inside and outside. While many homeowners concentrate on energy efficient appliances and maintenance, a little known technique is ignored and that is landscaping. Utilizing landscaping to change an environment is an old technique that our ancestors used for thousands of years. To understand how to use this technique, one must first explore their home’s surroundings.
Regional Climate
The United States is divided into four regional climates. Each climate has its own conditions that can be manipulated by landscaping. Knowing what regional climate applies to your living space is the first step in this process.
Temperate Region
This region goes from coast to coast and includes the Corn Belt. If you live in this area, the goal of an energy efficient landscape is to maximize the sun in the winter, provide maximum shade in the summer, deflect winds away from building in the winter and encourage summer breezes to funnel around the home.
Hot and Arid Region
This region includes the lower left hand portion of the United States from the lower part of California to the boundary of Texas. The landscaping goal of this area is to provide shade that will cover roofs, walls, and windows. Also, in this type of environment the goal is to allow summer winds to blow around and into homes that are cooled naturally. If the home is cooled by air conditioning, then the wind will need to be blocked or deflected away.
Hot and Humid Region
This region includes the lower right hand portion of the United States, which ranges from Texas to Florida. The goal of landscaping in this area is to channel the breeze toward the home and maximize shade in the summer while allowing the sun to penetrate during the winter. An important element of this region is plant placement. Since the area is humid, it is very important not to place plants that require watering near the home. If this is done, the humidity immediately around the home will be increased.
Cool Region
This region includes the most northern part of the United States, which encompasses Minnesota and Michigan. Energy efficient landscaping in this area should include dense windbreaks to protect the home from the cold winds of winter. The south side of the home should be open so that sunlight can reach the windows. If overheating is a problem, provide shade for the south and west facing windows.
Understanding your own climatic region is important but every home has its own microclimate that can change a landscaping strategy. Things to look for include the location of water, lay of the land, and surrounding vegetation. If your home is located near a body of water, then the humidity could be higher compared to what is in your region. Also the temperature may be artificially cooler then expected for the region.
The position or location of the home also affects the microclimate of the area. Homes placed on a southern slope tend to have warmer microclimates while those in a valley location are cooler. In addition, plant material that is around the home influences the microclimate. A home located in a dense grove of trees will have a cooler microclimate compared to one out in the open.
Once your own climate has been evaluated, it is time to explore two techniques used to create an energy efficient landscape.
The Science Behind Shade
While shade seems to be a simple concept, there does exist a science behind the shade. Shade is created when a tree overhangs something. This can be a person, place or home. When a tree shades something the temperature underneath the tree is cooler. This is due to the blocking of solar radiation and the natural process of evapotranspiration. This procedure is a natural part of the photosynthetic process where water is released through the plant’s leaves and evaporated. Through this evaporation process, water is released into the environment and in doing so cools it down. This cooling can be as much as 9 degrees Fahrenheit. Once the surrounding air begins to cool, it travels toward the ground. This is why seating under a tree is so refreshing in the summer. This cooling affect is enhanced the farther away one is from any hardscape, such as asphalt, concrete or bricks. If you are in a grassy area the temperature difference can be as large as 25 degrees Fahrenheit.
Before one thinks that planting a bunch of trees is all that is needed for an energy efficient landscape consider the shadow the trees will cast, the shape and size of the tree along with the density of the tree. All these factors play a role in the science of shade.
Home get heated up by the sun when solar radiation enters the home through windows and the heating up of the roof material. Shade can help reduce or prevent this invasion but to utilize this technique one must understand their need.
Homes that need protection from the sun year round will need to utilize evergreen trees and shrubs. This type of tree stays green year round and does not shed its’ leaves. On the other hand, homes that only need sun protection in the summer can utilize deciduous trees. These are trees that shed their leaves in the fall.
Not only do deciduous trees drop their leaves but they also form a crown that consists of branches. These branches in the spring and summer will be covered with leaves providing shade. If you need to shade your roof from the sun, then you will need a deciduous tree with a high spreading crown that is planted on the south side of the home. If you have a deciduous tree that has a shorter crown, plant this on the west side of the home. It will block afternoon sunlight, which is lower.
Creating a cooling environment can also be done by shading the hardscape around the home. This includes any type of pavement. Utilizing this technique will cool the air before it reaches the windows and walls of the home. Simply planting shrubs around a walkway or driveway will create a cooler environment. In addition, planting a climbing vine around a patio in a planter, in a window box or up a wall on a trellis is another way of cooling the environment.
The Science behind Windbreaks
Windbreaks not only break wind in the winter but in some area is a good technique to use when you want to prevent the warm winds of summer blowing into your home.
Windbreaks work by stopping the flow of the wind around your home. In the winter, the blowing wind causes the temperature to drop. A windbreak will slow the wind speed and in doing so reducing the wind chill factor. This reduction can be felt a substantial distance away from the windbreak and as a matter of fact the wind will be reduced the distance of 30 times the height of the windbreak.
To utilize this technique to its fullest, one must know the mature height of the trees that are going to be used for the windbreak. Once this is known, take that number and multiply it by two or five. This will give you the distance that the windbreak needs to be planted away from the home for the best results.
Windbreaks are not limited to a single type of vegetation. A mixture of tall trees and shrubs is the best approach to block the wind.
Evergreen trees and shrubs work well as a windbreak when planted along the north and northwest areas of the home and yard. Another approach one can use when dealing with evergreen trees and shrubs is to plant them along a wall or berm. This will create a ramp by which the wind can blow up and over the house.
If snow is a problem in your area, plant shrubs along the side of your windbreak that receives the most wind. This will trap the snow and reduce the amount that blows on your house.
To aid an insulating factor around your home, plant vines, shrubs, and bushes around the home. When using this approach, do not place them any closer to the home than one-foot. This will allow enough space for a pocket of air to form between the plant material and the home.
Energy efficiency not only occurs in the home, but outdoors. Depending on your region and microclimate, this will determine the approach you need to use. Keep in mind though that most climates need a combination of techniques for energy conservation.
ABOUT THE AUTHOR
Mindy McIntosh-Shetter has been an Agricultural Science educator, and is a horticulture and/or environmental blogger who earned a degree from Purdue University in Agriculture Education with a minor in biology, and natural resources. Presently she is finishing up her Masters in Environmental Education and Urban Planning for the University of Louisville while working on her own agriculture/environmental blog.
