A method of supplying an element for covering a non-vision area in a curtain wall on an architectural structure, comprising the steps of: (a) at a location remote from both a unitized curtain wall assembly shop and the architectural structure, prefabricating a plurality of shadow boxes by performing the following steps to assemble each of the plurality of shadow boxes: (i) sealing, with a first airtight and moisture resistant hermetic seal and a second airtight and moisture resistant hermetic seal, an interior spacer between a vision glass panel and a back structure, the spacer having a length so that the vision glass panel is spaced apart from the back structure, the back structure including a first insulating material and a rigid envelope disposed around the first insulating material, the spacer disposed along a peripheral edge of the vision glass panel and along a peripheral edge of the back structure so as to hold the vision glass panel in a spaced apart relationship from the back structure, so that the first hermetic seal seals the interior spacer to the vision glass panel and so that the second hermetic seal seals the interior spacer to the back structure and so that the vision glass panel, the back structure and the interior spacer define a hermetically sealed void therein; and (ii) applying a structural seal about the interior spacer and so as to be affixed to the peripheral edge of the vision glass, the interior spacer and the back structure; and (b) delivering the plurality of shadow boxes, after being prefabricated, to a selected one of the unitized curtain wall assembly shop and the architectural site. (a) at a location remote from both a unitized curtain wall assembly shop and the architectural structure, prefabricating a plurality of shadow boxes by performing the following steps to assemble each of the plurality of shadow boxes: (i) sealing, with a first airtight and moisture resistant hermetic seal and a second airtight and moisture resistant hermetic seal, an interior spacer between a vision glass panel and a back structure, the spacer having a length so that the vision glass panel is spaced apart from the back structure, the back structure including a first insulating material and a rigid envelope disposed around the first insulating material, the spacer disposed along a peripheral edge of the vision glass panel and along a peripheral edge of the back structure so as to hold the vision glass panel in a spaced apart relationship from the back structure, so that the first hermetic seal seals the interior spacer to the vision glass panel and so that the second hermetic seal seals the interior spacer to the back structure and so that the vision glass panel, the back structure and the interior spacer define a hermetically sealed void therein; and (ii) applying a structural seal about the interior spacer and so as to be affixed to the peripheral edge of the vision glass, the interior spacer and the back structure; and (i) sealing, with a first airtight and moisture resistant hermetic seal and a second airtight and moisture resistant hermetic seal, an interior spacer between a vision glass panel and a back structure, the spacer having a length so that the vision glass panel is spaced apart from the back structure, the back structure including a first insulating material and a rigid envelope disposed around the first insulating material, the spacer disposed along a peripheral edge of the vision glass panel and along a peripheral edge of the back structure so as to hold the vision glass panel in a spaced apart relationship from the back structure, so that the first hermetic seal seals the interior spacer to the vision glass panel and so that the second hermetic seal seals the interior spacer to the back structure and so that the vision glass panel, the back structure and the interior spacer define a hermetically sealed void therein; and (ii) applying a structural seal about the interior spacer and so as to be affixed to the peripheral edge of the vision glass, the interior spacer and the back structure; and (b) delivering the plurality of shadow boxes, after being prefabricated, to a selected one of the unitized curtain wall assembly shop and the architectural site.