Landscaping Your Home for Energy Efficiency
Tagged as: Energy Efficiency
How does landscaping help?
Landscaping enhances your home, not only by improving its appearance and creating useful outdoor spaces, but also by helping to maintain comfortable indoor living spaces. Careful selection, placement, planting, and care of trees, shrubs, and vines can help you reduce your energy costs:
- In Winter, by maximizing solar heating while deflecting winds away from your home; and
- in Summer by maximizing shading while funneling breezes toward your home.
The US Forest Service reports that three optimal and well-placed landscape trees can reduce the annual costs of heating and cooling a well-insulated northern Illinois house by about 6.5%.
Winter and Summer: Seasons of Extremes
In an adequately insulated home, more than half of the heat gain can be attributed to sunlight streaming through windows. In summer, sunlight absorbed through the roof may be responsible for most of the remaining heat gain.
Open-branched deciduous trees (that drop their leaves in the fall) can effectively block sunlight in the summer, but not in the winter when solar heat is most desirable. Even bare branches of trees can block some winter sunlight so it is best not to shade solar panels.
Evergreen trees or shrubs to the north, west, and east of your home will provide some summer shade and be effective cold-weather windbreaks to minimize winter heat loss, without interrupting warm from the low, winter sun in the southern sky.
Shrubs and small trees near your home's foundation provide shade, windbreak, and additional insulation. Foundation plantings can trap a layer of air next to your home to buffer the effect of outside air temperatures on indoor temperatures. Allow at least one-foot clearance between the exterior wall and mature plants for maintenance and to prevent damp, stagnant conditions that can be damaging. Avoid shading south-facing windows with evergreen plants.
An Energy-conserving Landscape Plan
||Plant an evergreen windbreak to the north and northwest of you house to minimize winter winds.|
||Plant shorter shrubs on the windward (from which the wind is blowing) side of your home to trap snow before it can blow and drift against your home.|
||Plant deciduous trees with high spreading crowns to the south where the sun is highest in the sky at mid-day and most intense. (Recommended Plant List #1)|
||Plant shorter or low-branched deciduous trees on the west side to provide shade from the lower angles of afternoon sun. (Recommended Plant List #2)||
||Plant small trees or large shrubs to shade an outside air-conditioning condenser to increase its operating efficiency; allow a 3 foot clearance for proper air flow.|
Landscaping for summer shade
In summer, the shade from trees, shrubs, and vines block heating sunlight from reaching your home. To plan an effective energy-saving landscape, you should know how the shadows cast by trees and shrubs can change in size, shape, and location relative to your home as the sun moves throughout the day and seasons. Reference The Morton Arboretum's plant selection brochures for information about the size and growing habits of recommended landscape plants. Additional shading of walls can be achieved with climbing vines, particularly deciduous vines on southfacing walls and evergreen vines elsewhere (Recommended Plant list #3).
Plants also can cool the surrounding air through "evapotranspiration," This process, which is similar to the cooling process of sweating, removes heat from the air by absorbing water from the ground and releasing it as vapor from the leaves. Use plants to shade bare ground for additional cooling through evapotranspiration.
Plant to shade paved areas, such as driveways, patios, and sidewalks. These large surfaces absorb significant amounts of solar energy during the day and then heat the air by reradiating it during the day and night.
It may seem desirable to plant the fastest-growing trees for shade, however, these tend to be short-lived, have weak or brittle wood easily damaged in storms, and is susceptible to disease and attack by insects. Choose trees with moderate growth rates instead, as they are generally sturdier and more pest resistant.
Landscaping for winter wind protection
In the Chicago area, an effective windbreak blocks north and northwest winds near the ground and deflects them up and over nearby structures. Evergreen trees or shrubs planted in two or three staggered rows, or deciduous trees and shrubs with low-branched crowns planted in five or six rows, work well.
Landscaping for energy benefits to the community
With the common goal of energy conservation, your community can work together to create and maintain landscapes that provide significant shared benefits.
In suburban neighborhoods, for example, common areas bordering multiple properties can be planted to provide windbreaks (and noise barriers) for many homes more efficiently than would be possible in one small yard. In urban areas with more closely spaced homes, your neighbor's yard might provide the best location for a tree to shade the west side of your home in summer, while trees and shrubs in your yard might provide the best windbreak for their home in winter.
And, at a larger scale, increasing the amount of tree cover in a community can mitigate the "urban heat island effect", the tendency of settled areas to absorb and retain heat that makes them 5-9º F hotter than surrounding landscapes.
#1 Open-branched deciduous trees for southern exposure:
Freeman Maple (Acer xfreemanii)
Ohio Buckeye (Aesculus glabra)
Shagbark Hickory (Carya ovata)
Northern Catalpa (Catalpa speciosa)
Thornless Honey Locust (Gleditsia triacanthos var. inermis)
Kentucky Coffeetree (Gymnocladus dioicus)
Oaks (Quercus spp.)
Elms (Ulmus spp. - disease resistant cultivars)
#2 Low branched trees for western exposure:
Ruby Horsechestnut (Aesculus x carnea)
Serviceberry (Amelanchier x grandiflora or A. laevis)
European Hornbeam (Carpinus betulus)
American Hornbeam (Carpinus caroliniana)
Cornelian-Cherry Dogwood (Cornus mas)
Winter King Hawthorn (Crataegus viridis 'Winter King')
Magnolias (Magnolia spp. - hardy varieties)
Crabapples (Malus spp. - disease resistant cultivars)
Peking Lilac (Syringa pekinensis 'Morton')
Japanese Tree Lilac (Syringa reticulata)
Other landscape objectives, such as maintenance, appearance and plant health need to be considered in an energy conserving landscape plan.
Your city or village can assist you in planting appropriate trees on parkways and other public areas. For information on selecting, locating, planting, and maintaining trees and shrubs in the Chicago region, visit The Morton Arboretum's website www.mortonarb.org or contact The Morton Arboretum Plant Clinic in Lisle, Illinois, at 630-719-2424.
Additional information on landscaping for energy efficiency is available from the U.S. Department of Energy (enter the search term 'landscaping') or at the US Forest Service Center for Urban Forest Research.