New Study: Home Energy Savings Are Made in the Shade

[OKIsItJustMe]

http://www.nist.gov/public_affairs/techbeat/tb2009_0505.htm#shade

New Study: Home Energy Savings Are Made in the Shade

Trees positioned to shade the west and south sides of a house may decrease summertime electric bills by 5 percent on average, according to a recent study* of California homes by researchers from the National Institute of Standards and Technology (NIST) and the U.S. Department of Agriculture (USDA).

The first large-scale study of its kind, the research paper considers the effects of shade on 460 single-family homes in Sacramento during the summer of 2007 and provides hard statistics showing how well-placed shade trees can reduce energy costs and atmospheric carbon, as well.

“People have known for a long time that trees have multiple benefits for people, but we’ve quantified one of them for the first time using actual billing data and put a dollar value on it,” said NIST’s David Butry, who authored the paper with Geoffrey Donovan of the USDA Forest Service’s Pacific Northwest Research Station.

The study’s findings included:

• Planting trees on the west and south sides of a house decreased summertime electricity use, but planting them on the north actually increased it. Those on the east had no effect.
• Fast-growing trees provide better help than do smaller ones, and placement of the trees, particularly the distance from the house, is a significant factor.
• A London plane tree, planted on the west side of a house, can reduce carbon emissions from summertime electricity use by an average of 31 percent over 100 years.

This last finding was particularly significant to Butry, who said that trees not only reduce the carbon produced by the local gas or coal-fired power generator, but also remove carbon dioxide—a greenhouse gas—from the atmosphere.

“Trees sequester carbon in addition to providing shade,” Butry said. “We measured how much these shade trees reduced the carbon created by burning fuels to produce the electricity, and found that the trees also sequestered an equivalent amount of carbon on top of that. So there’s a double benefit.”

Utility companies from as far away as South Korea and South Africa have contacted the team about expanding the study, which was limited to a single season in a single city.

“It would be really interesting to look at how the effect varies across regions of the U.S. and of the world, and to see what happens in wintertime,” Butry said. “Sacramento Municipal Utility was very helpful in providing us with the data we needed. But future studies will depend on who has data and shares it with us.”

* G.H. Donovan and D.T. Butry. The value of shade: Estimating the effect of urban trees on summertime electricity use. Energy and Buildings June, 2009, 662-668. doi: 10.1016/j.enbuild.2009.01.002.

Media contact: Chad Boutin, [email protected], [phone]

[Ian David]

1. Until there is a hurricane. n/t

[Andy823]

3. I don't worry about hurricanes

But the winters of 2006 and 2007 were really windy around my area. Trees feel in 2006 and took out power lines and fell on numerous houses. We had a huge spruce on the west side of out house that did block a lot of summer sun, but after two winters of worrying about it coming down on our house, we took it out last fall. I did get a lot of firewood out of it for the fireplace this coming winter! :woohoo:

[DCKit]

5. You've got to plant the right-size trees Ian.

There are plenty of trees that never get more than 25'-40' tall and lots of shrubs you can plant that will shade the ground and keep heat from radiating into the house even after the sun is gone. I'm intending to plant a forest around my next place so I can laugh at the weekend warrior lawn jockeys while picking fruit from my landscaping.

But yeah, replacing a roof is more expensive than any single year's AC costs - for now, anyway.

[kristopher]

6. Paulownia is a very good, fast growing shade tree in that range

http://en.wikipedia.org/wiki/Paulownia

[Tumbulu]

7. I planted one and it is not as fast growing as the native Sycamore

but it is very very pretty with sweet smelling flowers. I do love the tree and it is not slow growing. The best quick shade around N. California are the Sycamores (they call them Plane trees in this article) the male mulberry, climbing wisteria on a trellis or arbor on the south/west side. I have been experimenting with this for quite some time. Female mulberries, although not such a quick shade produce the very very best fruit in the world full of antioxidants, so perhaps a faster growing female mulberry is know by posters.

But I do think looking for trees that grow no taller than 40 ft is a good idea around houses.

[MADem]

2. Awnings are useful, too, if trees are impracticable. nt

[pscot]

4. The American Institute of Standards and Technology

and the Department of Agriculture have labored mightily and produced a study which finds that it's cooler in the shade. Mercy, mercy. Next they'll be telling us to come in out of the rain.

[Fledermaus]

8. I have never recommend cutting down trees to add solar panels.

I chose trees over solar panels on my roof. I have the equipment and I know how to perform solar surveys. I will not cut down a thirty year old pecan tree to install a solar array on my roof. I purchase wind power from my utility and I am using my money to increase the efficiency of my home.

This pecan tree shades my house in the summer. It provides food in the fall. The leaves fall off in the winter time and allows the sun to warm my house. I use a mulching mower on the dead leaves to add soil carbon to my lawn. I use the dead limbs to make bio char and use it to grow tomatoes, bell peppers, cucumbers, and water mellon. Try doing that with a solar array. God has been in the solar business for billions of years. What we try do do in comparison is amateurish at best.

I never recommend cutting down trees to add solar panels.