Apparatus and components for multi-pane window assembly and window insert

A multi-pane window assembly comprising:

• a multi-pane window having a plurality of glass panes and a preformed window frame;
• and
• a multi-pane window insert, the multi-pane window insert comprising:
• a first pane and a second pane formed of polycarbonate resin thermoplastic material;
• a spacer frame retaining and providing structural support for the first pane and the second pane, wherein the spacer frame separates the first pane from the second pane, wherein the spacer frame is formed of resin thermoplastic material, the spacer frame, first pane, and second pane defining an exterior perimeter surface, an interior facing side, and an exterior facing side;
• and
• a gasket comprised of a flexible material and formed on the exterior perimeter surface, the gasket comprising a flat surface adhered to the exterior perimeter surface, a second surface having a substantially convex shape defining a gap with the flat surface, and an elongated protrusion extending from the second surface on the interior facing side and being configured to provide an air-tight seal for the multi-pane window insert when installed in a preformed window frame, wherein the gasket is formed of a different material than the first pane, second pane, and the spacer frame;
• wherein the multi-pane window insert is configured to be installed on an interior surface of the pre-formed window frame such that when the second surface of the gasket abuts the pre-formed window pane the gasket is flexed to flatten the gap to provide the air-tight seal.