HORTICULTURE: Planting for Efficiency

Plants do more than beautify a landscape. The right material planted in the right place promotes energy efficiency in clients’ homes, reducing the use of costly heating and cooling systems. This is an environmental benefit contractors should promote, says John Keller, director of research for Monrovia Growers, Azusa, Calif. “Consumers are very aware of the importance of energy savings and reducing their impact on the environment,” he says. “Contractors should consider offering homeowners a landscape energy audit with a free evaluation of how they could reduce their energy use through landscaping.”
 
While all vegetation has carbon-reducing benefits, trees are a landscape’s biggest energy       

saver. “The simplest way contractors can promote energy savings is by using trees to provide shade that reduces the demand for air conditioning,” Keller says. “Trees do this by shading the home directly, and by shading the paving and concrete in a typical urban landscape, reducing the so-called ‘heat island’ effect. They also cool the air through evapotranspiration.”
 
Experts at The Davey Institute, Kent, Ohio, communicate the benefits of healthy trees to their clients through marketing materials and face-to-face conversations. The message is well received, says Greg Ina, general manager, as clients recognize the energy-saving benefits, as well as the increases to property value. “People are responding to the dip in housing values and also have personal interests in energy abatement and lightening their environmental loads,” he says. “Eco-friendly landscaping allows them to increase their property’s curb appeal and lower their eco-footprint at the same time.”

 
According to the Environmental Protection Agency, a building’s shaded walls may be 9 to 36 degrees cooler than un-shaded surfaces. Studies have shown that by shading 20 percent of a home – the equivalent of planting one tree to the west and another to the south – homeowners could see annual cooling savings of 8 to 18 percent and annual heating savings of 2 to 8 percent. Total energy savings depend on a tree’s density, shape, placement, the building’s dimensions, sun position and whether the tree is deciduous or evergreen.
 
Shading a home’s windows and roof is the best way to reduce energy consumption. According to Saturn Resource Management, an energy conservation research company, tall trees with spreading canopies block sun best, particularly during summer months when the sun is high. Tall trees should be planted 10 to 25 feet from a home’s south side to shade the south-facing windows and the roof. This prevents summer and midday sunlight from overheating a home, while letting in low-angle, heat-generating sunlight during winter months.
 
Broader, shorter trees are useful for managing lower-angle sun, which occurs in the morning and evening during all seasons, and throughout the entire day in winter. Broad trees should be planted 20 to 50 feet from a home’s east and west walls to block the morning and evening sun that overheats a home during the summer months. These trees then allow the sun in during cold winter days. LL