A display case door assembly for a temperature-controlled storage device includes a frame defining an opening into the temperature-controlled storage device and a transparent unit coupled to the frame. The transparent unit includes a first vacuum pane, a second vacuum pane, and an evacuated gap between the first and second vacuum panes. The evacuated gap has a predetermined thickness within which a vacuum is drawn, thereby providing a thermal insulation effect for the transparent unit. The transparent unit further includes a plurality of spacers disposed within the evacuated gap and configured to maintain the predetermined thickness of the evacuated gap when the vacuum is drawn therein.