PURPOSE: To stick a heat insulating sheet simply on a glass surface, and cut off heat transfer by mounting a meshy spacer combined with a transparent or semitransparent synthetic resin sheet to a window or door glass fixing surface.

CONSTITUTION: For example, a window is mounted to one side 10A of a window glass 10 in an openable manner. At that time, a synthetic resin sheet 22 is placed to the outside from the glass surface 10A to provide a meshy spacer 24 as a unit between the synthetic resin sheet and glass surface 10A. At that time, an adhesive 26 is applied to the glass surface 10A side of the spacer 24, and a glass heat insulating sheet 20 is fixed to the glass surface 10A to provide an air-layer 28 between the glass surface 10A and synthetic resin sheet 22. As a resin material, a transparent or semi-transparent synthetic resin material having a free light absorption characteristic is used. The air layer 28 displays heat cut-off performance to increase the initial heat insulation property of the window glass 10 or synthetic resin sheet 22 to the extent of approximate two times thereof. According to the constitution, the effect of heat insulation is doubled, and energy can be saved in the case a room is heated in wintertime.