AERC Rates, Labels and Certifies the Energy Performance of Window Attachment Products for Commercial Applications

The importance of energy efficiency in a building can’t be overstated for the building’s occupants. The window industry has made impressive progress in manufacturing increasingly energy-efficient products and providing consumers with credible information about product performance through rating and certification programs, such as ENERGY STAR and the National Fenestration Rating Council.

Window attachment products, including commercial secondary glazing systems, blinds, shades and shutters, represent areas ripe for additional savings and performance ratings of these attachment products.

Secondary glazing systems—also known as low-e storm windows, insulating panels or secondary windows—are a cost-effective, high-performance energy-saving alternative for commercial buildings with older, less-efficient windows.

Secondary windows attach to the interior or exterior of an existing window and create an insulating pocket of air between the existing window and secondary window. They can incorporate low-e coatings for even greater performance. This results in improved occupant comfort, reduced heating and cooling usage, and lower costs. In fact, for mid- to large-sized commercial buildings with lower-performing windows, secondary windows can achieve excellent results in a very cost-effective manner. According to the Northwest Energy Efficiency Alliance, secondary window systems can help buildings cut energy use by up to 20 percent and are about half the cost of a window replacement.

Analysis conducted by the U.S. Department of Energy has shown that window attachments have the potential to save significant energy in residential and commercial buildings. As a result, in 2014, the Attachments Energy Rating Council (AERC) was formed. AERC is an independent, non-profit organization whose mission is to rate, label and certify the energy performance of window attachment products for residential and commercial applications.

AERC was formed with funding provided by DOE and the window attachments industry and has the support of organizations, such as Lawrence Berkeley National Laboratory, Oak Ridge National Laboratory, Intertek and other energy-efficiency organizations that assist AERC in developing test methods, simulation models and certification procedures.

AERC launched the Commercial Secondary Window Program in 2020 alongside its existing residential products program. AERC recognized the potential of secondary windows and prioritized the development of a rating and certification program to provide the industry with credible data about the energy performance of these products.

“The DOE recently analyzed 400 energy-efficiency technologies and ranked interior and exterior storm windows No. 2 in their potential impact,” says Paul Hagar, AERC’s marketing director. “Everyone in- volved with saving energy in buildings will want to know how much energy storm windows can save, and AERC’s third-party testing and validation provides trusted data that lets energy-efficiency professionals understand the tremendous energy savings storm windows offer.”

To achieve AERC commercial certification, products must be evaluated against AERC’s technical standards to assess key performance metrics, including U-factor, Solar Heat Gain Coefficient, Visual Transmittance and Air Leakage. All product performance is independently verified by Intertek, a third-party administrator, before products can earn AERC certification.

Three manufacturers were early adopters of the AERC program and earned the first AERC commercial certification in the industry at the end of 2020. Four interior storm window products from Larson Manufacturing Co., two interior and two exterior products from QUANTA Technologies Inc., and two window insert products from Indow Windows are now certified through AERC. (See “AERC-certified Secondary Window Systems,” next page.)

“As AERC certification is more widely used and recognized, architects, contractors, building owners and facility managers will have a better way to compare products apples to apples,” explains Sam Pardue, CEO and founder of Indow Windows. “Product testing can be done differently by different manufacturers, which can result in misleading comparisons. By having a way to validate that data—that products are being tested under the same conditions—stakeholders and decision-makers are now able to make informed, comparative decisions.”

David Bailey, division manager for Larson Manufacturing, agrees: “Certification has given Larson’s team the ability to highlight energy savings of the certified products and present product claims in a substantiated way that contractors, building owners and architects can trust. The certification process assures the energy performance of the products, and end-users can know that products are certified to perform to levels stated by the manufacturer.”