Arboriculture & Urban Forestry 35(4): July 2009 Arboriculture & Urban Forestry 2009. 35(4): 197–202 197 An Experimental Analysis of the Impact of Tree Shade on Electricity Consumption David N. Laband and John P. Sophocleus Abstract. Trees cast shade on homes and buildings, lowering the inside temperatures and thus reducing the demand for power to cool these buildings during hot times of the year. The potential monetary savings may be sizable, especially for those who live in hot climates, because electricity usage for cooling residential and commercial structures in summer months is costly. A controlled experiment was conducted to quantify the impact of tree shade on electricity consumption devoted exclusively to cool- ing a structure. We examine electricity consumption used to run air conditioning units set at identical temperatures in two other- wise identical buildings, one set in full sun, the other in full shade during the summer months of 2008 in Beauregard, Alabama. The building in full sun required 2.6 times more electricity for cooling than the building in full shade. Our findings contrib- ute to a growing body of research which demonstrates that owners of residential and commercial properties located in hot re- gions can reap sizable monetary savings from shade trees that serve as natural complements to their artificial air-conditioning. Key Words. Energy Savings; Natural Cooling; Tree Shade. Trees affect the well-being of humans in a variety of ways. In large measure, the impacts are positively-valued. For example, trees are aesthetically pleasing, are a source of energy for heating and cook- ing, provide habitat for other plant and animal species valued by humans, are a source of certain foods and medicines, and provide natural filtration that helps clean water and reduces destructive stormwater runoff. However, in some respects the impacts are neg- ative (e.g., trees fall on power lines, cars, and occasionally people, they may enhance risk of fire, and heavy tree shade may increase the amount of electricity needed to adequately light a structure). Most of these economic values have not been measured/es- timated. However, a number of researchers have examined the impact of urban trees on residential energy consumption. Trees cast shade on homes and buildings, lowering the inside tempera- tures and thus reducing the demand for power to cool these build- ings during hot times of the year. The potential monetary sav- ings may be sizable, especially for those who live in hot climates, because electricity usage for cooling residential and commercial structures in summer months is costly. In the Sun Belt region of the U.S., the energy used for air conditioning makes up a large fraction of the peak electrical utility loads during the warmest pe- riod of summer (Rudie and Dewers 1984). As the cost of electric- ity continues to climb, the economic incentive for homeowners to find ways to conserve on energy use grows correspondingly. This paper presents the results of a controlled experiment conducted to quantify the impact of tree shade on electric- ity consumption devoted exclusively to cooling a structure. LITERATURE REVIEW Because residential demand for electricity depends on a large number of factors, most analysis of the link between urban tree canopy and residential energy usage has been based on simula- tion exercises. For example, Huang et al. (1987) conducted a simulation study of the potential role of vegetation in reducing summer cooling energy in residential houses located in Lake Charles, Louisiana; Los Angeles, California; Phoenix, Arizona; and Sacramento, California (U.S.). The simulations suggest that an additional 25% increase in tree cover would reduce an- nual cooling energy use by 40%, 25%, and 25% for an average house in Sacramento, Phoenix, and Lake Charles, respectively. However, the calculated savings for Los Angeles were mini- mal. Simpson and McPherson (1996) used simulation analysis to suggest that two trees shading the west-facing exposure of a house and one tree shading the east-facing exposure would re- duce annual energy use for cooling by 10% to 50% and peak electrical use up to 23%. Similarly, McPherson et al. (1997) es- timated that three 7.6 m (25 ft) tall trees around a well-insulat- ed new house located in Chicago, Illinois would reduce annual heating and cooling costs by 8% as compared to an otherwise identical house without trees. Akbari et al. (1997) analyzed the impact of shade trees on peak power and cooling energy use in two houses in Sacramento, and found a 30% reduction in energy use and 0.6 to 0.8 kWh peak demand savings due to shade trees. In a compelling analysis, Rudie and Dewers (1984) exam- ined the impact of shade cast in different coverage categories on energy consumption by 113 residences in College Station, Tex- as. Over a three-year period (1977–1979), they used measured tree height to estimate the amount of shade cast on roofs on the 21st day of June, July, August, and September. They developed a shade score for each home ranging from 1 to 4 based on the shaded roof perimeter and wall space, and classified each home into one of 4 shade categories to analyze energy savings as a re- sult of tree shade. Their findings for different shade categories indicated that the amount of shade, roof color, and wall color were significant determinants of residential energy consumption. ©2009 International Society of Arboriculture
July 2009
| Title Name |
Pages |
Delete |
Url |
| Empty |
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success. You will be contacted by Washington Gas with follow-up information regarding your request.
This process might take longer please wait
