Windows, especially single-pane windows, are the weakest energy efficiency link in a building envelope. Secondary windows can improve performance without the expense of window replacement. Researchers from the Pacific Northwest National Laboratory evaluated ultralight insulating panels that attach to existing windows and maintain window operability. They found that the technology was easy to install and improved the window’s insulating performance by 52%. During the webinar, researchers and GPG representatives will share operational guidance, discuss findings from project evaluations, and answer questions.