Insulation barriers incorporating a cementitious structural matrix formed from a cementitious mixture including a hydraulic cement and water. The insulation barriers are manufactured from cementitious materials in order to be lightweight, insulative, less expensive, and more environmentally compatible than those currently used; they may augment, and even take the place of, traditional insulation materials including insulations made of glass fibers, polyurethane foam, urea-formaldehyde foam, polystyrene, wood fiber, cellulose fiber, rock-wool, etc. The cementitious structural matrix of the insulation barriers usually includes a hydraulic cement paste (formed from the reaction of water with, e.g., a portland-type cement) in combination with a rheology-modifying agent, such as methylhydroxyethylcellulose, and a lightweight aggregate material, which lowers the density of the insulation barrier and increases its insulation ability. Fibrous materials may be incorporated into the cementitious mixture to increase the strength of the final product, while a discontinuous phase of nonagglomerated voids may be incorporated into the cementitious structural matrix to decrease the density and increase the insulation ability of the final product.