Abstract: A size-adjustable construction element involves use of channel spacers to maintain spaced parallel relationship and positive physical contact between adjacent panel members. A preferred embodiment of the invention comprises multilayered mirror insulation having an adjustment section to permit use of a standard size component to fit nonstandard dimensions and further includes channel spacers that effectively reduce convection between adjacent layers, provide positive structural support, provide a bearing surface for ease of adjustment and maintain the parallel space relationship between adjacent sheets.