The present invention relates to fiberglass loose-fill insulation that is insensitive to the content of boron in the composition of the glass. It has been discovered that the level of boron in the glass used for the manufacture of loose-fill glass wool can be substantially reduced without degrading thermal performance. The lowered amount of boron provides for a lower cost batch composition and increased furnace life. The glass composition of the present invention includes a substantially reduced content of boron and preferably an increased amount of sodium dioxide. The primary phase of these glass compositions is typically devitrite (Na.sub.2Ca.sub.3Si.sub.6O.sub.16). The glass of the present invention provides a glass fiber blowing wool that does not require an increase in pack density to compensate for the reduced boron content while achieving the similar thermal conductivity. The glass of the present invention is also suitable for use in acoustic insulation.