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Keep Your Cool

July 2, 2010

I took my kids to the zoo today.

And it was hot.

While 81 degrees really isn't that scorching, the humidity was 90 percent. It was muggy - that kind of humid where your skin feels sticky and clammy, your breath short, your clothes clingy and your feet heavy.

Leaving a group of Orangutans, and feeling even hotter after watching them swing through the trees in their reddish-brown coats, we walked down a path with sides lined with magnificent overarching maples. A verdant umbrella of complete cool swept through the passageway as the faint wind seemed that much more empowered. The burning sunlight was muted and instead played softly on the leaves, their corresponding shadows dancing on the ground. I stopped with my arms spread, closed my eyes and just enjoyed the breeze like in a scene from a movie.

Ah, the power of trees in the summertime.

It's true.

"Trees take up water in their roots and it transpires through their leaves, which results in a cooling effect," explains Scott Maco, manager of ecosystem services at The Davey Institute, Kirkland, Wash.

Basically, trees sweat, he says.

An acre of maple trees can put as much as 20,000 gallons of water into the air each day, studies says.

Just as trees cool an area around them, they also can cool your home. Trees placed on the west side of a home can reduce a homeowner's summertime electric bill by $25 a year, according to a 2009 USDA Forest Service study of 460 homes in Sacramento, Calif. And air conditioning needs can be reduced by 30 percent.

Shade trees reduce heat gains by 40 to 80 percent (depending on their placement and density), and air conditioners cooling a fully shaded house work only half as much as those in a house that has its walls and roof exposed to the sun, say experts at the Louisiana State University Extension.


While west is the No. 1 spot for tree placement for the purpose of cooling a home, Maco says the east side of a home is also a good placement for a tree. The goal is to find a balance of coolness in the summertime mixed with solar access in the wintertime to limit how much a homeowner runs the heat as well, reducing overall energy use.

And in an urban area, Maco says trees can cool a city's temperature by one, two or even up to a few degrees. Think Central Park in New York City or any well-canopied neighborhood or tree-lined street.

Well-maintained trees obviously provide more benefits than poorly maintained trees because they are healthier, have a more full canopy and live longer, driving the benefits, Maco adds.

Feeling the heat? Want to take advantage of the shade? When landscaping for energy conservation, the right placement, as well as number and type of trees is crucial. And summer is a great time to decide where you need shade.

Generally, medium-sized trees (those that grow 30 to 55 feet tall) are suitable as primary shade trees on an average urban lot, Louisiana State University Extension agents say. Avoid trees 60 feet or taller or those with a spread of more than 40 feet unless you have property large enough to accommodate them. Small, 15- to 20-foot trees are suitable for planting closer to the house or shading smaller locations like a patio or deck area. Many other characteristics, such as wind tolerance, bloom time and type, growth rate, bark interest, overall form, berries or nuts and fall color, are also important to consider.

By cooling the air and ground around them, the shade from trees helps cool the Earth's temperature - and the people who endure its highs and lows.

Now if only I can figure out how to take a tree along with me to the zoo to keep the family cool the entire day. Maybe I'll just plan my next route around the zoo to include regular rest stops under my shade-producing friends.

Want to figure out how much your current trees or planned tree additions help cool your home and save energy? Visit the National Tree Benefit Calculator. It allows anyone to make a simple estimation of the environmental and economic benefits individual street-side trees provide. Just type in your zip code, tree species and tree size and you'll get an idea of the annual monetary value of your trees.


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