Abstract: A modular, block-shaped insulating unit for use in an insulating system for the interior of a high-temperature furnace or the like. The module comprises a plurality of short, ropelike lengths formed of braided strands, assembled in side-by-side relation to form a bundle. The strands are formed of twisted, generally parallel ceramic fibers spun into cords and assembled or braided into a rope, which is then cut into generally equal lengths. The lengths are retained in a tightly compacted condition whereby the ends of the fibers define a front planar face of the module, with the fibers being aligned in a generally perpendicular orientation relative to the front planar face.