Abstract: A thermal insulation system for insulating a pipe is disclosed having an upper insulation member engageable with a lower insulation member to collectively surround the pipe. Each of the upper and lower insulation members preferably have a plurality of constant radius relief cuts at each end thereof, wherein the constant radius relief cuts extend from the end of each of the insulation members toward the center of the insulation member. In a preferred embodiment, each insulation member further includes a plurality of radial relief cuts extending radially from the inner surface of each of the insulation members toward the outer surface of the insulation member. The radii of curvature of the insulation members is preferably variable such that, for a portion of the insulation member, a gap exists between the inner surface of the insulation member and the pipe, allowing room for fluctuation in the size and shape of the insulation members.