An example of a vertically operating door includes a flexible panel comprising two pliable sheets of material with a plurality of pads or mats of thermal insulation between the two sheets. In some examples, a plurality of horizontally elongate baffles made of pliable strips of material are installed between the two sheets. The baffles effectively divide one large interior volume between the sheets into more manageable smaller volumes or chambers. The baffles restrict the air between the sheets from being forced to the bottom of the panel as the panel ascends and bends across an overhead roller. Without the baffles and smaller chambers, the panel sheets in the area near the bottom of the panel would tend to bulge outward as the door opens.