A new awning energy study shows residential cooling energy savings across the U.S.
By Michelle Sahlin
The Professional Awning Manufacturers Association’s (PAMA) Awning Energy Study 2012: The Impact on Energy Use and Peak Demand of Awnings and Roller Shades in Residential Buildings provides data on how the use of awnings and roller shades affects cooling energy savings and utility costs in 50 cities across the U.S. The Awning Energy Study 2012 expands the scope of a previous study, conducted in 2007 by the Center for Sustainable Building Research at the University of Minnesota, and considers new variables: shade designs, fabrics, the number of cities and a model house. PAMA contracted with Joe Huang, White Box Technologies, Moraga, Calif., to conduct the new study. An expert in building energy simulation, Huang has dedicated much of his professional career to using simulations to study the effects of various building components on building energy use. He was also instrumental in conducting the 2007 study.
A primary objective for the new study was to extend the analysis beyond the 12 locations in the 2007 study. A list of the top 50 metropolitan population centers across the U.S. was used.
This study also considers two awning types and exterior roller shades made of several fabric types, two types of operations (cooling season only or all year), and two weather conditions (typical year and an unusually hot year), and since the performance of the awnings and exterior roller shades is strongly related to the window conditions and orientation, this analysis considered three types of windows and four window orientations.
While the previous study used a dark-colored acrylic stationary (traditional) awning with sides, the new study considers stationary awnings with a 90-degree drop and a drop-arm awning with both a 90-degree drop and a 165-degree drop in both black and linen acrylic fabrics. It also considers exterior roller shades fully extended over the window in five fabric choices. The fabrics were tested for solar transmittance, openness factor, visible light transmittance and shade coefficient. These variables were used in a simulation using the DOE-2.1E building energy simulation program developed for the U.S. Department of Energy by Lawrence Berkeley National Laboratory (LBNL) to model building energy performance.
While the 2007 study considered energy savings for newer construction and a larger home (2,000 sq. ft.), the new study considers an older house, which is 10% smaller (1,700 sq. ft.) and has less insulation. The resulting data helps support awnings and shades as “smart,” retrofit products to help make older houses more energy efficient. The impact of increased electrical rates—up as much as 10% since 2007 in some cities—was also considered. Energy savings is an ongoing nationwide hot topic being discussed by energy departments, utility companies, architects, designers, home owners and builders at local, state and national levels. Data showing the energy savings of awnings and solar shades is valuable for providing energy solutions for both new and existing housing stock. According to LBNL, buildings consume 40% of energy, or 71% of electricity, in the U.S. Two percent of the nation’s energy is used to cool houses, and window construction and attachments can significantly impact the cooling, heating and lighting of buildings.
The Awning Energy Study 2012 shows that average cooling energy savings with the use of awnings can range from 17–72% in a house with equally distributed windows during a typical year depending on the city. In cities where little air-conditioning is used (San Francisco, Seattle, Portland, Ore., Anchorage) there may be little savings in corresponding kilowatt hours. In these locations, awnings may be used for reasons other than energy savings, such as comfort from direct sun (UV rays), aesthetics, visual comfort (glare) and even protection from gentle rain.
Average cooling energy savings for exterior roller shades can range from less than 1% to 33%, depending on the location, in a typical year for a house with equally distributed windows. Taking weather conditions into account, the study shows that on average, the hottest year caused average awning cooling costs to be 50% higher than in a typical year and the savings due to shading was 27–40% higher. Plotting the cooling energy savings of window awnings on the map shows significant savings across the Sun Belt.
In a typical year, awning cooling energy savings for a house with equally distributed windows in Chicago, for example, can range from 41–57% compared to a house with unshaded windows. The corresponding dollar savings are $44-64. In a hot year the cooling energy savings ranges from 31–48% compared to a house with unshaded windows, with corresponding dollar savings of $41–91.
While the findings are based on a specific model and are not guaranteed for every home, awning and roller shade companies can use the results for the cities they service to educate local energy influencers and help discuss the benefits of their products to their customers. The complete report, including data for individual cities, is posted on the PAMA website.