Abstract: The structures and preparations of high R-value, low-cost, light-weight, durable, removable, and transparent window insulation panels are disclosed. The panels are made of spaced and parallel double or multiple layers of transparent plastic sheets, air-tightly mounted on to a frame of plastic, wood, aluminum or other materials. The frame of the panels has seals on the sides for air-tight fitting into the interior structure of the windows, and has different shapes, colors and styles, if necessary, to match the design of the windows. The panels can also be designed to fit into the interior structure of glass doors to provide supplementary insulations. The panels can increase the R-value of double pane windows or glass doors from current about 3 to up to 8 or more, dramatically reducing energy losses.