Shade from trees provides an inexpensive way to keep your yard and home cooler and more comfortable. On a scorching summer day when the air temperature out in the sun is 100 degrees, the surface temperature of a black asphalt roof is over 140, and an asphalt driveway over 120 degrees. Shade provided by trees can reduce these extreme temperatures, resulting in a more comfortable yard for outdoor activities and a house that is easier to cool. A 10% savings in cooling costs would help the family budget, but savings as high as 50% have been documented.
When planning a landscape for shade production, prioritize areas that get the highest heat gain. Here are some tips:
- For your home, trees on the east and west sides will provide the best protection from direct solar gain. A tree planted 10 feet from a wall will provide twice as much surface shading as one 20 feet away.
- 3/4 of total solar heat gain in a building comes through windows, so shade them.
- Provide shade for areas that hold a lot of heat, such as driveways and parking areas.
- High summer use areas such as patios and porches benefit highly from shading.
- Shading an air conditioning unit can increase its efficiency by 10%.
Tree species with broad, dense crowns when mature offer the best shading potential. Trees planted close to your home should have strong wood. As a rule, fast growing trees have weaker wood.
The following is a comparison of the relative shade value of several popular trees. Highest shade value species include Maples, Hackberry, Beech, Green Ash, Walnut, Yellow Poplar, and Sycamore. Medium shade species are Sweetgum, Oaks, Kentucky Coffeetree, Cottonwood, and Elms. Those lowest in shade value include hickories, catalpa, ginkgo, locust, Goldenrain tree, Pears, and Hawthorns.
A good information source for using trees to save energy all year long is Tree City USA Bulletin #21, published by The National Arbor Day Foundation, 100 Arbor Ave., Nebraska City, NE 68410. It can be seen on their website at http://www.arborday.org/programs/treeCityUSA/bulletins/browse.cfm.