In 1980, just before I started my insulation business, I visited a local cellulose manufacturing plant to inspect their quality control procedures as I was trying to decide whose product of 3 competitors I would install*. In the plant office was a picture of a horse drawn insulation blower supposedly taken in Philadelphia in the 1930’s.
*(Note: They were very surprised…no other insulation contractor had ever done this before. Ended up being taken to dinner by the plant owner to discuss the industry. He actually made me an offer to manage the plant as he lost his manager the week before!)
Dense pack cellulose would be blown through 2-3 inch holes as it takes much larger equipment to get the higher densities to do the top airsealing job. The one inch holes would be for those using the smaller electric powered blowers. These units can get the densities needed to prevent settling, if the holes are spaced appropriately. Air leakage is reduced at these densities also but not as much. In 2 two storey houses, I have measured air leakage reduction by just blowing at the lower densities and found 39% and 34% reductions in total house air leakage.
NOTE: Don’t replace windows for air leakage reduction and energy savings only…it’s a long payback. Window/ door air leakage in houses is uusally 10-15% of total leakage…work on the worst areas, of which the attic is #1 or 2.