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Landscaping: Considerations for Energy Efficiency


With the onset of warmer weather and longer days, many homeowners turn their attention to the exterior of their home. Spring projects often include cleaning up the yard, applying grass seed, mulching flower beds, and planting pretty annuals for spring and summer color. If you're planning a landscaping project this spring, keep in mind that the types of trees and bushes you select, as well as their placement, can affect your home's energy efficiency.

The sun's rays can heat your home through windows and your roof. Solar heat gain is the amount of solar radiation transmitted or absorbed through your window's glass and released as heat inside your home. This can be desirable in the winter, but not so much in the summer. 

Windows that face the south and east get the most direct sunlight. If there is nothing blocking that sunlight, those rooms can benefit from additional heat generated by solar heat gain during the winter months.  But with heat of the summer in the Maryland, Virginia, and Washington DC areas, this can make the rooms uncomfortably warm and overwork your air conditioner trying to cool them down.

When planning the location for new trees and shrubs, pay attention to where shadows fall. And keep in mind that these shadows will fall in different places throughout the year due to the changing angle of the sun. You'll want to plant trees to block the sun from directly hitting your home, especially in the warmer afternoon hours. While a new tree may only be eight to ten feet tall initially, it will shade your windows right away. But in a few years, the added height will begin to shade your roof. Tree species with high spreading branches will maximize the amount of shade hitting your roof as well, helping to keep your home cooler. 

By planting deciduous trees, which lose their leaves in the winter, you can block summer sun, but allow some desirable solar heat gain in the winter. When trees lose their leaves, coupled with the lower angle of the winter sun, this will still allow plenty of sunlight to reach your windows. And trees and shrubs planted near your home have the added benefit of deflecting cold winds away from your home.

While we're on the topic of shading your home from the summer sun, take a look at your outside air conditioning unit. If properly shaded, it will run more efficiently than if the summer sun was beating down on it. By shading the area where your air conditioner is located you can increase its efficiency up to 10%. When all is said and done, well-planned landscaping can reduce an unshaded home's cooling costs by 15-50%.