A machine for packing compressible low density loose fill cellulose insulation material into flexible bags. A machine includes a hopper for receiving bulk quantities of loose fill insulation material. A metered feed mechanism is sequentially operable to discharge measured amounts of the loose insulation material from the hopper to an upright charging tube. Below the tube is mounted a container receiving mechanism and a container enclosure mechanism. Empty flexible insulation receiving bags are mounted to the receiving mechanism and located in position directly below the charging tube. The enclosure mechanism is operated to close about the periphery of the empty container while a compactor mechanism operates to compress the preselected amount of insulation into the waiting container. Once the container is packed, the enclosure mechanism opens to allow the filled container to be removed and an empty container mounted in its place.