An insulation product especially suited for use as an aircraft insulation includes a blanket of randomly oriented entangled glass fibers bonded together by a thermosetting binder and having a mean diameter of about 1+/-0.25 microns. The blanket has a density between about 0.25 and about 1.5 pounds per cubic foot and a thickness between about 0.35 inches and about 2.0 inches. The blanket, exclusive of anything else, has an average machine direction tensile strength of at least 0.6 pounds/inch of blanket width and an average cross machine direction tensile strength of at least 0.3 pounds/inch of blanket length; a transverse airflow resistance between about 300 Rayls and about 1800 Rayls; and a thermal conductivity equal to or less than about 0.32 BTU-in/hr-ft.sup.2 -.degree. F. The glass fibers of the blanket have a biodissolution rate in excess of 150 ng/cm.sup.2 /hr.