A geothermal heat containment barrier operable to be manipulated through an opening of a vault by at least partially folding the geothermal heat containment barrier, and positioned substantially horizontally against walls of the vault to reduce heat transfer through the barrier is provided. The barrier includes a central insulating core, a flexible outer frame, and an outer sealing trim. The central insulating core includes top and bottom outer surfaces and a perimeter edge. The central insulating core includes and/or contains an insulating material. The flexible outer frame has a shape memory and includes at least one flexible component having ends together such that the flexible outer frame is continuous and closed. The outer sealing trim is attached to the top and bottom outer surfaces and wraps around the perimeter edge of the central insulating core. The outer sealing trim is operable to press against the wall of the vault.