The approach of summer has many gardeners turning their attention to planting plans. If your goal is energy efficiency, landscaping can not only beautify your home, but help you control future energy costs for years to come.
According to researchers at the Depart-ment of Energy’s National Renewable Energy Laboratory, trees carefully positioned around a home can save as much as 25% of household energy consumption for heating and cooling. Shrubs can help control costs by diffusing wind or solar heating, thereby moderating the transfer of heat.
Meet Your Microclimate
For years, gardeners have used the U.S. Department of Agriculture’s Hardiness Zones as guidelines for plant stock selection, seasonal cultivation and projected harvest. But understanding the impact of nearby vegetation, topography and soil science will help you know your yard better, providing flexibility for landscape planning and potentially more options for using plants to control energy costs.
Other factors influencing microclimate are the duration and intensity of sunlight over areas considered for planting, and proximity to topographic or vegetative wind breaks or wooded areas, which can regulate local temperatures by several degrees.
Trees at the Top
No matter how much you love trees, you will want to plant them at a distance.
Placed too close to foundations, pavement and plumbing, root systems or maturing branches can damage foundations or roofs.
Never plant trees close to power lines. Always consider their mature height, and make sure they will not grow into lines.
Planted in the right place, in five to 10 years a fast-growing shade tree can reduce outside air temperatures near walls and roofs by as much as 6 degrees Fahrenheit on sunny days. Surface temperatures immediately under the canopy of a mature shade tree can be up to 25 degrees cooler than surrounding shingles or siding exposed to direct sunlight.
According to the Department of Energy, deciduous trees—those that lose their leaves in autumn—are great options for seasonal summer shade. Tall varieties planted to the south of a home can help diffuse sunlight and shade the roof.
Shorter varieties of deciduous trees can be planted near exposed west-facing windows to help shade homes on summer afternoons. Mass plantings of evergreens selected for their adaptability to regional growing conditions can be planted further away on a north or northwest section of a yard to form a windbreak, shielding the home from winter winds.
Deciduous trees with high, spreading crowns—leaves and branches—can be planted to the south of your home to provide maximum summertime roof shading. Trees with crowns lower to the ground are more appropriate to the west, where shade is needed from lower afternoon sun angles.
Trees should not be planted on the southern sides of solar-heated homes in cold climates. The branches of deciduous trees will block the winter sun.
Using shade effectively requires you to know the size, shape and location of the moving shadow your shading device casts. Homes in cool regions may never overheat and may not require shading. You need to know what landscape shade strategies will work best in your climate and microclimate.
Trees are available in the appropriate sizes, densities and shapes for almost any shade application. To block solar heat in the summer, but let much of it in during the winter, use deciduous trees. To provide continuous shade or to block heavy winds, use dense evergreen trees or shrubs.
Although a slow-growing tree may require many years of growth before it shades your roof, it will generally live longer than a fast-growing tree. Because slowgrowing
trees often have deeper roots and stronger branches, they also are less prone to breakage by windstorms or heavy snow.
Trees, shrubs and ground cover plants can shade the ground and pavement around the home. This reduces heat radiation and cools the air before it reaches your home’s walls and windows.
Use a large bush or row of shrubs to shade a patio or driveway. Plant a hedge to shade a sidewalk. Build a trellis for climbing vines to shade a patio area.
To ensure lasting performance of energy-saving landscaping, use plant species that are adapted to the local climate. Native species are best because they require little maintenance once established and avoid the dangers of invasive species.
Properly selected, placed and maintained landscaping can provide excellent wind protection, or windbreaks, which will reduce heating costs considerably. The benefits from these windbreaks will increase as trees and shrubs mature.
Climate Strategies
The energy-conserving landscape strategies you use depend on where you live. With a little research and planning, you’ll be well on your way to a beautiful, energy-efficient lawn.
The United States can be divided roughly into four climate regions: temperate, hot-arid, hot-humid and cool. Below are suggested landscaping strategies listed by
region and order of importance.
Temperate
- Maximize warming effects of the sun in the winter.
- Maximize shade during the summer.
- Deflect winter winds away from buildings with windbreaks of trees and shrubs on the north and northwest side of the house.
- Tunnel summer breezes toward the home.
Hot-Arid
- Provide shade to cool roofs, walls and windows.
- Allow summer winds to access naturally cooled homes.
- Block or deflect winds away from air-conditioned homes.
Hot-Humid
- Channel summer breezes toward the home.
- Maximize summer shade with trees that still allow penetration of low angle winter sun.
- Avoid locating planting beds close to the home if they require frequent watering.
Cool
- Use dense windbreaks to protect the home from cold winter winds.
- Allow the winter sun to reach south-facing windows.
- Shade south and west windows and walls from the direct summer sun if summer overheating is a problem.