Abstract: A unique one-piece molded insulating and drainage panel for use for basement subterannean walls is disclosed. The panel is molded from expanded polystyrene having very low water permeability. When installed, the panel has two sides having vertically oriented grooves on both sides. The grooves abutting the foundation wall are typically rectangular whereas the vertical channels on the outside wall are specifically designed to be self-clearing to avoid blockage by backfill. Typically a bell-bottom shaped narrow opening and a wider inner channel is used.