Insulation panels are for use in providing a gas insulation layer between a surface and a liquid having a low boiling temperature. The insulation comprises a cellular or honeycomb core having a plurality of discrete cells enclosed by a capillary cover with capillary openings communicating with each cell. The honeycomb core is tensioned and also is shaped to an arcuate or concave configuration before the capillary cover is adhesively secured thereto. The adhesive forms a smoothly radiused joint between the core walls and the capillary cover with the adhesive being feathered on the cover and the walls immediately adjacent the joint. Vacuum is applied to each cell to form a dimple in the capillary cover and the capillary openings are then formed in the cover. A filler material may be placed in each cell and a backing sheet applied to the core to maintain the filler in the cells and facilitate assembly of the panel to the surface to be insulated. Each cell may be tested individually by applying a vacuum to the capillary opening associated with that cell and, if a leak between the capillary cover and the core is detected, the portion of the cover over that cell may be removed and a predimpled cover patch secured over the cell.