Purdue specialist: Choose, plant trees wisely for energy efficiency

April 9, 2015  


WEST LAFAYETTE, Ind. - Homeowners can make their yards not only more attractive but their homes more energy-efficient by planting the right trees in the right place, a Purdue Extension urban forestry specialist says.

Lindsey Purcell said trees create a cooling effect during the hot summer months and allow for passive solar gain - heat directly from the sun after leaves have fallen - during winter months.

"However, proper selection and placement is critical to make this work," he said.

Purcell noted that trees offer many functional and aesthetic benefits, shade being the most common. Because of this, proper placement of the tree is essential.

"The tree can actually become a liability if it conflicts with infrastructure or just does not provide any useful shade at all," he said. "For shade where it's needed most that also allows passive solar gain in the winter months, you must use an energy-efficient design."

Purcell offered this advice in selecting and planting trees:

* Select good-quality trees that are suitable for your location from a reputable source.

* When choosing trees for shade and solar gain, select larger, deciduous-canopy trees primarily for the south-facing side of the house, then on the west and east. In the summer, when the sun is high in the southern sky, the leaves will provide shade and, as a result, help cool the house. In the winter after the trees have lost their leaves and the sun is lower in the sky, openings such as windows will allow for direct heating, provided the openings are not blocked, such as by foliage and other vegetation.

* On the north side of the house, minimize exposure to prevailing winter winds with evergreen-type trees. Purcell advises against planting evergreen trees near the house on southern exposure. "Such trees may provide some shade and screening, but they will also block out the warming effects of the sun during winter months."

* Be sure the height and spread of the tree when mature will fit the location before planting it. This will allow the tree to spread into the design space naturally without excessive pruning that would be needed to prevent conflicts with the house.

But Purcell noted that the tree still must be close enough to the house for the canopy to provide shade. "A good rule of thumb is to plant the tree at least 20 feet from the house. For larger shade trees, you may need to plant as far as 40 feet from the house to ensure room for growth."

Purcell provides additional guidance in a posting titled "Plant for the Sun" on the Purdue Department of Forestry and Natural Resources blog "Got Nature?," at www.purdue.edu/gotnature. The posting includes a diagram of proper tree placement near a house.

Additional information on tree selection and planting is in the free publication FNR-433-W, available on the website of Purdue Extension's The Education Store at www.edustore.purdue.edu.           

Writer: Keith Robinson, 765-494-2722, robins89@purdue.edu 

Source: Lindsey Purcell, 765-494-3625, lapurcell@purdue.edu

Ag Communications: (765) 494-2722;
Keith Robinson, robins89@purdue.edu
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