An insulation system for a concrete block having an open end and a closed end, the insulation system including a single sheet of a foam material configured to have opposite end portions with a middle portion intermediate the end portions and a hinge defined between each of the end portions and the middle portion to enable the sheet to be folded so that the middle portion is disposed perpendicular to the end portions to render the sheet in a u-shaped orientation so as to be insertable into the open end of the concrete block; and a panel of foam material configured as a rectangle to conform to the closed end of the concrete block. The sheet of foam material is sized to provide a snug interference fit with the open end of the concrete block when folded into the u-shaped orientation and the panel is sized to provide a snug interference fit with the closed end of the concrete block. The sheet of foam material and the panel of foam material are each made of a closed cell flexible foam.