According to research conducted by the Center for Sustainable Building Research (CSBR) at the University of Minnesota, awnings have the potential to contribute to more sustainable buildings. Residential window awnings, in particular, lend themselves to a number of environment-friendly benefits.
First, awnings can reduce the amount of cooling energy used by residential buildings by blocking much of the direct sunlight and heat that would otherwise come through the windows. This reduction in energy expenditure has the potential to result in reduced mechanical equipment costs, as less demand is placed on cooling equipment. In addition, if more homes were to install window awnings, the reduced demand on the power grid could help utility companies keep up with rising demand in the future and reduce carbon emissions.
The CSBR looked at homes in 12 cities with a variety of different climate conditions to study the exact effects of window awnings on energy savings. What they found was that while the direct savings varied, reduced demands were experienced in all climates, especially for homes with west-facing windows and during peak demand times.
The cities with the highest actual energy savings were predominantly those with hot and dry climates, like Phoenix, Arizona. In this city, energy savings were shown to vary between 13 and 31 percent, depending on the time of day tested and the primary orientation of the windows in the home. While this does not represent the city with the highest percentage of cooling savings, because of high amount of energy used to cool residential buildings in a climate like Phoenix’s, this savings was the greatest in the actual cooling energy and peak demand savings. In a home with mostly west-facing windows, for example, the cooling energy with awnings was reduced to 6046 kWh from 8122 kWh, which is a savings of 2076 kWh, or 26 percent.
In a cold climate, however, leaving awnings up for 12 months out of the year significantly reduced their usefulness, as the energy gains made in the summer were lost in the winter since the window awnings blocked passive solar heating. Home owners in climates with cold winters would do well to install retractable awnings that can be used during the summer, but put away during the winter.
While the study did not look at other sun-blocking devices like patio covers, it seems likely that the same types of benefits could be expected from this equipment as well. Home owners who want to save money on cooling, especially those in warm climates without much humidity, can use window awnings for this purpose.