An insulated panel includes a first layer defining an inner surface; a corrugated medium defining a plurality of peaks, the plurality of peaks attached to the inner surface, a plurality of flutes defined between the corrugated medium and the inner surface; and an insulation material at least partially filling a flute of the plurality of flutes.

Cardboard with edges sealed by a mixture of hot-melt adhesive and wax includes two surface sheets and an intermediate core material. The surface sheets have a pair of corresponding edges that form an edge opening therebetween communicating with the interstitial spaces in the cardboard and sealed by an edge-sealing structure in the interstitial spaces. The edge-sealing structure includes a primer layer formed by an adhesive mixture and a sealing layer formed by a sealing mixture. The adhesive mixture is made by mixing the hot-melt adhesive with the wax, adhesively bonds the surface sheets and the intermediate core material together, and forms the primer layer with voids and providing a porous supporting surface to be coated with the sealing mixture. The sealing mixture is less adhesive than the adhesive mixture and fills up the voids in the primer layer. Thus, the cardboard achieves waterproofness and thermal and acoustic insulation at low cost.

An insulated panel includes a first layer defining an inner surface; a corrugated medium defining a plurality of peaks, the plurality of peaks attached to the inner surface, a plurality of flutes defined between the corrugated medium and the inner surface; and an insulation material at least partially filling a flute of the plurality of flutes.