Home Ownership Like internal insulation, energy-efficient landscaping should reduce air infiltration and prevent radiant heat loss. Air infiltration, which can account for as much as half of your heating bill, increases with wind velocity. In addition, high winds increase heat loss through window glass and create eddying currents on the windward side of the house. In winter, evergreen trees not only break the wind; they also reduce radiant-heat loss to the cold night air. In summer, deciduous trees shade your roof and windows from the sun.

Careful planning is essential to successful energy-efficient landscaping. If you plant your rows of trees and shrubs in the wrong place, you can end up with a net heat loss. Note the wind currents around your house. For maximum protection, the windbreak should be on the windiest side (usually the north and west sides of your lot) and 1.5 to 2.5 times the height of the house away.

This distance allows the windbreak to deflect the wind up and over your house, reducing pressure on the building's windward side and the pulling action on its leeward side. A windbreak reduces wind speed for a distance of about 20 times the height of its tallest tree.

The best windbreaks are several rows of trees, with the tallest ones closest to the house. Because they allow some wind to pass through, trees make better windbreaks than solid walls. When wind hits a vertical wall, it drops quickly on the other side, causing strong eddying currents on the leeward side. Whatever you do, don't put a square of trees all around your house. Blowing snow will be deflected up over the windbreak and then drop right on your roof.




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Home > Home Ownership > Energy Economics > Energy - Efficient Landscaping

December 4, 2008