cardboard
Sheets or panels of corrugated or thickened paper used for thermal insulation.
Cardboard is a material formed by joining sheets of thick paper, usually corrugated paper lined with flat sheets for structural strength. It is an inexpensive material of medium insulation value, but must be protected from flames and moisture.
The sheets are used as panel insulation. Corrugation is usual, with flat lining sheets giving the paper assembly strength and a continuous face.
The insulating material remains paper-based even when assembled as a stiff board. Its susceptibility to flame and moisture distinguishes its protection needs from those of mineral or synthetic foam panels.
