Reading the Commercial Certificate

AERC’s third-party rating and certification program, developed with support from the U.S. Department of Energy (DOE), has been designed to offer independent and accurate information about the energy performance of window attachment products.

The AERC Energy Performance Certificate presents several measurements relevant to the energy performance of secondary window products. Secondary windows are the first AERC rated and certified product category in the commercial space, providing performance data such as U-Factor, Solar Heat Gain Coefficient, Visible Transmittance, and Air Leakage. Please refer to the technical glossary for definitions of these measurements.

How Products Earn the AERC Certificate

Products with AERC certified ratings have been tested and simulated according to stringent standards. AERC then reviews and accepts the results before ratings are published. A summary of the process appears below as it relates to secondary window products. The AERC Certification Program page provides additional details.

Material Testing: An approved test lab measures the thermal and optical properties of the glazing or other similar materials used in commercial secondary windows. Test results are peer reviewed and then published either in the Complex Glazing Database (CGDB) or the International Glazing Database (IGDB). Both databases were developed and are actively managed by Lawrence Berkeley National Laboratory (LBNL).

Product Ratings:

  • Simulated Ratings: An AERC Accepted Simulator models and simulates the performance of the product over a single-pane, aluminum frame baseline window to generate U-Factor, Solar Heat Gain Coefficient, and Visible Transmittance.
  • Air Leakage Testing: An approved test lab measures the air leakage of the commercial secondary window product.

Validation and Certification: ratings submitted to AERC undergo a third-party independent validation to affirm their accuracy prior to certification. Certified products approved by AERC can be found on the Certified Product Search

Ongoing Review: Manufacturers with certified products are subject to annual review, either through in-plant inspections or verification testing of certified products, to affirm their manufacturing processes and sourcing practices match their rated product design

If you have questions or would like further information or assistance in understanding the ratings, please contact us.

How to Read the AERC Energy Performance Certificate

The AERC Energy Performance Certificate provides key information about a product’s certified energy performance ratings, divided into the following sections:

  • Product Information: This section provides basic information about the certified product, including the AERC Number (which you can use to search for the product on the Certified Product Search), in addition to basic information about the manufacturer and product design.
  • Product Ratings Installed Over Base Window: This section provides key information about the energy performance of the certified product. The column titled, “Primary Baseline Window” describes the energy performance of the baseline window without the addition of the certified commercial secondary window. The column titled, “With Secondary Window Addition” lists the energy performance ratings of the baseline window WITH the certified commercial secondary window. The product ratings are presented next to the baseline window ratings to demonstrate the relative energy efficiency improvements offered by the certified product. Reference the technical glossary for more information about each rating. Note that the scale of ratings varies by how the metrics are measured. Some (such as solar heat gain coefficient) use lower numbers to represent better performance. Others (like visible transmittance) use