Growth Spurts

There are many reasons to plant trees and shrubs around the home, but one that we may not immediately think of is the benefit landscaping has on energy savings. Well placed trees and shrubs can help reduce heating and cooling costs. Factors to consider when planning the landscape are the angle of the sun, orientation of the house and direction of winter and summer winds.
Providing shade can significantly reduce the heat flow into a home. Studies suggest shade can reduce heat flow by as much as two-thirds. Likewise, shading roofs with tall, high branching trees such as oaks can help with cooling. While summer shade is desired to reduce cooling expenses, we also want to maximize winter sun. To get the best of both worlds requires careful tree selection. Characteristics to look for include high branches to block summer sun, but permit winter sun, which strikes the house at a much lower angle. Open branching such as that of the Kentucky Coffee tree allows for a more open winter canopy and allows greater winter sun penetration. We also want to consider the timing of leaf drop. Ideally, look for trees that drop leaves between October 15 and November 15. We want to avoid trees with cone-shaped crowns, such as pin oaks and many evergreens. These provide significantly less shade in summer and block winter sunlight. Consider shading south facing walls as well west facing walls which capture a great deal of heat from the hot afternoon sun.
Wind is another consideration in landscaping to conserve energy. Homes lose much more heat on cold windy days than on cold still days. Well placed trees and shrubs can intercept winter winds and reduce heat loss. Identify the direction of winter winds in your area. Typically, the coldest winds arrive from the north and northwest and so a windbreak is best located along the north and west edge of the property. Wind speed increases at the ends of the wind break, so ideally, the windbreak will extend beyond the area of concern.
Evergreen trees provide the best protection from winter winds, though densely branched deciduous trees can also reduce wind speeds. High and plant density are the most important factors to consider when selecting plants to reduce wind. Place the windbreak at a distance from the house that is equal to two to five times the mature height of the windbreak tree species. Where space is a concern, try a narrow, upright cultivar such as the skyrocket juniper.
In spaced-limited landscapes, vines can also be used to shade south and west-facing walls. Vines that cling to trellises are preferred over those that climb directly on walls as plants that climb walls can cause some deterioration to wood. Evergreen vines should not be used on south facing walls as they block winter sun. However, evergreen vines are ideal for blocking winter winds in a small landscape. Placing vines on trellises, arbors or fences on the north and west sides of the home help to insulate against winter winds.
Foundation plantings are the plant materials placed along the perimeter of the home. Foundation plantings impact the energy gain and loss from a home in a variety of ways. They act as insulation against wind, reducing air currents close to the home. They also create pockets of air that act to insulate the home. As with wind breaks, evergreens have a greater impact on energy savings than deciduous plants.
As you plan the landscape, consider the addition of trees and shrubs to help conserve energy. Protect the home from northwest winter winds, and shade the south and southwest walls from summer sun. The benefits in energy savings will pay for the plants in the long run. 
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If you have questions concerning this topic or related topics, call the OSU Extension Center at 273-7683.