An aluminum secondary glazing is a custom-made, lightweight aluminum-framed window installed on the interior of an existing window to create a second pane of glass, improving thermal insulation and soundproofing without altering the original window. It is a discreet, cost-effective, and reversible solution, often used in listed buildings or when complete window replacement is not feasible. These windows are available in various styles, including sliding, hinged, and lift-out, and can be customized with different glass types and colors to suit the existing property.