Awnings provide cool solutions for homeowners
PAMA’s Awning Energy Study II shows residential cooling energy savings
in fifty U.S. cities.
By Michelle Sahlin
The Professional Awning Manufacturers Association’s (PAMA) Awning Energy Study II: 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 II 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.
The study’s scope
In the previous study in 2007, only a traditional stationary awning (90 degree extension covering half of the window) was analyzed for 12 representative locations. 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.
In order to properly weight the heating penalties against the cooling savings, as well as give a sense of the dollar amount of benefits, the prices for electricity and natural gas were needed. The study based utility prices on the latest information from the Energy Information Agency (EIA), which lists the average utility prices by state in 2010.
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 square feet), the new study considers an older house, which is 10 percent smaller (1,700 square feet) 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 percent since 2007 in some cities—was also considered.
Indications
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 percent of energy, or 71 percent 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 II shows that average cooling energy savings with the use of awnings can range from 17–72 percent 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 percent to 33 percent, 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 percent higher than in a typical year and the savings due to shading was 27–40 percent higher. Plotting the cooling energy savings of window awnings on the map shows significant savings across the Sun Belt.
Likewise, deployment of exterior roller shades can have a significant effect on home cooling energy in a hot year. The study shows that cooling energy savings average 15–33 percent for a house with equally distributed windows.
In a typical year, awning cooling energy savings for a house with equally distributed windows in Chicago, for example, can range from 41–57 percent 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 percent 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, and will be made available to the public later this summer.
Let the sun shine
Results for a typical year vary among the regions surveyed, but awnings and roller shades consistently provide cooling energy savings—no matter where you live.
Central/North Central
- Awnings: 43 percent
- Exterior shades: 28 percent
North/Northeast
- Awnings: 42 percent
- Exterior shades: 25 percent
Sunbelt
- Awnings: 25 percent
- Exterior shades: 19 percent
West/Northwest
- Awnings: 51 percent
- Exterior shades: 22 percent
