Energy Saving Window Inserts, also known as interior storm windows or panels, are custom-fitted acrylic panels designed to press into the interior frame of existing windows, creating an additional airtight layer of insulation that traps a pocket of still air between the insert and the original glass—much like adding a secondary pane without the expense or disruption of full window replacement. A snug fit that seals out drafts, blocks heat transfer, and significantly boosts a window's R-value (often doubling insulation for single-pane windows), making them ideal for older or historic homes where preserving original architecture is key. These inserts excel at reducing energy loss—studies from the U.S. Department of Energy and independent tests show average savings of 30% on heating and cooling bills by minimizing HVAC strain—while also delivering secondary benefits like up to 70% noise reduction for quieter interiors, UV blocking to protect furnishings, and reduced condensation that prevents mold and window damage.