The Northwest Energy Efficiency Alliance (NEEA), an alliance of more than 140 utilities in the Northwest, engaged Evergreen Economics to conduct a characterization study of the market for secondary windows. The purpose of the study is to aid in the development of a program intended to transform the market so that secondary windows become the standard product and practice for addressing low-performing windows in existing commercial buildings. "Commercial secondary windows are retrofit products that enhance the performance of an existing window without a full replacement or reglazing. They can be added to existing windows with poor energy performance to mitigate air infiltration, energy loss, or unwanted solar gain, while also offering non-energy benefits to building occupants, thereby offering a lower cost alternative to window replacement. Secondary windows are appropriate for windows with single panes and, in some cases, those without low-emissivity coatings that were introduced in 1979 and became commonplace after 1990. In contrast to other window attachments like window film, coverings, and shading devices, secondary windows add additional layers of glazing (and framing) to the interior or exterior of the existing window. They are historically related to storm windows used in residential buildings, but are designed and custom-produced for commercial applications. They can be constructed to offer add-ons such as multiple panes, low-emissivity coating, or gas-filled cavities to further enhance their performance and energy savings." Read the entire report here.