December 3, 2016

Landscape for Looks & Efficiency

Wise landscaping can lower utility bills and improve comfort in addition to dressing up your property.

Q: We are landscaping our new house and want a wooded yard for shade and to enhance the energy efficiency of our home. Where should we plant trees, and which are best? What materials are good alternatives to grass for ground cover?

A: Wise landscaping can do more than create an attractive yard. It can lower your utility bills, summer and winter, and improve your family’s comfort year-round. Trees, being one of the key components of any residential landscaping design, can have the greatest affect on your utility bills.

For one, the evaporation of moisture from tree leaves actually cools the air temperature around your home, akin to how perspiration cools your skin. With the proper placement and selection of trees, you can use less electricity to heat your home by taking advantage of passive solar heating during winter.

The primary goal of efficient tree landscaping is to shade your home during summer, yet allow the sun to pass through during winter. Additional goals are, depending on your climate, to allow cool evening breezes to flow around your house or provide moisture for evaporative cooling of the air near it.

Before you start, determine your temperature zone by visiting the USDA Agricultural Research Service at planthardiness.ars.usda.gov/PHZMWeb/# or checking with a local landscaper. Hardiness zones refer to the minimum winter temperature range. For warm climates in Zone 10, the range is 30 degrees to 40 degrees F. For cold climates in Zone 1, the range is -30 degrees to -40 degrees F. Michigan ranges from Zone 4a to 6b, depending on the area you live in. If you select trees that thrive in a climate more than one or two zones outside your range, they may not do well and require excessive care.

In an average temperate climate, a typical efficient tree landscaping plan has deciduous trees to the south, southeast and southwest. The leaves block the sun during summer, but when the leaves fall, the sun shines through to heat your home. Leave a small gap to the southwest to allow cooler evening breezes to flow through.

Plant dense evergreens along the north, northeast and northwest sides to block cold winter winds. With shorter days and the sun riding lower in the winter sky, not much solar heat comes from these directions.

In hot, humid climates, shading during summer is most important. Taller trees should be planted closer to the home to block the sun, which is higher in the sky. Leaving a gap for breezes is not as important.

There are also alternatives to grass, such as ground cover plants and gravel. Both have advantages and disadvantages for landscaping a house. The benefits of either depend on your climate, house and yard. Even in the same neighborhood, what’s good for one house may not be efficient for another.

Low-growing ground cover near your house can help to keep it cool. The leaves block the sun’s heat from absorbing into the ground, and they give off moisture for natural cooling. This cooling effect is most effective in drier climates because there is more evaporation. In hot, humid climates, the additional moisture from plants near the house actually increase the relative humidity level. This is more of a problem if you rely on natural ventilation compared to air-conditioning with the windows closed.

A good location for low ground cover is between an asphalt or cement driveway or walkway and the sunny side of your house. The driveway gets hot and holds the heat, and also re-radiates it up to your house.

– James Dulley is a nationally recognized mechanical engineer writing about home energy issues for the National Rural Electric Cooperaive Association. Send inquiries to James Dulley, Michigan Country Lines, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit dulley.com.