West is best
Shade west and east windows to most effectively reduce air conditioning use:
- Give highest priority to planting shade trees next to west windows.
- Plant trees next to east windows as a second priority
- Select a tree that can be planted within twenty feet of a window and will grow at least ten feet taller than the window.
- Select trees that are strong, resistant to disease, pests and dam age from storms; and that will grow vigorously under local site conditions.
- Select a tree with dense foliage, as broad in form as space permits.
Let the sun shine in
Avoid shading south windows.
If trees already exist south of windows:
- Remove their lower branches to allow more winter sun under the limbs.
If you do want a tree southeast or southwest of a window:
- Use a "solar friendly" tree that has moderately dense foliage during the hottest times of the year, loses its leaves early in the fall as the heating season begins, and has sparse winter branches.
- Select cultivars from northern seed sources which will lose their leaves earlier in the fall.
Remember: Take advantage of the free solar energy coming in through the south windows in the winter. The worst place to have a tree is in the yard south of a home, since the sun's angles cause the shadow of the tree to miss the home during the summer months and always fall on the home during the winter months.
The more the merrier
Maximize tree canopy cover throughout the neighborhood to maximize environmental benefits.
- Achieve at least 50% tree canopy cover by planting trees throughout the neighborhood.
- Preserve and care for existing trees and forests near neighborhoods.
- Locate air conditioners away from south windows and shade them with trees allowing good air circulation around the air conditioner.
- Shade car parking areas with trees which have enough rooting space to thrive.
Up and over
Where winters are long and windy, the most valuable way to reduce annual energy use is to create windbreaks. Tall trees will guide wind up and over an area to a point downwind at least ten times the height of the windbreak.
- Select windbreak trees which are evergreen and which will have branches from ground level to a height at least twice as tall as the building being sheltered.
- Select trees that are best adapted to the site's growing conditions so they will be tall, yet dense.
- Plant rows or continuous clusters of trees upwind and perpendicular to the primary wind direction usually running along the west and north sides of the property.
If your lot is very large:
- Make the windbreak longer than the area being sheltered
- Space evergreens about 20 feet apart and deciduous trees at greater spaces to allow the sun to reach the lower branches; where space is limited, plant fewer trees - don't crowd the trees.
- Locate the inside of the shelterbelt on a very open site at least 50 feet from buildings and driveways to avoid snow drifting problems, even if the windbreak is on the other side of the road.
If your lot is smaller:
- Plant evergreen trees to the west and north in sunny locations in rows or groupings with trees spaced about ten feet apart.