A thermal insulation article includes a thermally insulating pad shaped to be positioned in a cavity of a rectangular prism shipping container. The pad includes a solid compostable panel formed primarily of starch and/or plant fiber pulp that holds together as a single unit, and a water-proof or water-resistant film forming a pocket enclosing the panel. The panel includes a first section, a second section, and a third section connecting the first section to the second section, the first and second section each having a central portion and two flaps that extend from the central portion beyond the third section, and wherein the panel is foldable into an open box.