My contractor blew the cellulose in from outside the house. He cuts two 1 inch diameter holes per bay, and uses a flexible tube to fill in each bay. The blower he used is a 240 volt, high capacity machine, looks like a shop vac on steroids, probably cost 2 to 3 thousand dollars. Also includes a controller at the point of filling, so a single person can operate the machine.
The key to avoiding settling is to achieve about 120 percent of normal density of the cellulose. If you achieve less than 100 percent, the cellulose will settle over time, leaving a void at the top of each bay. This obviously diminishes the insulation value tremendously. In order to get 120 percent normal density, you need a high pressure blower, as I previously noted. This means at least 2.5 psi, maybe 3 psi.
The typical blower rented by Home Depot produces somewhere around 1 psi, which is fine if you are blowing loose insulation into the attic, where settlement is not a problem. However, the typical rental blower cannot achieve the required density in vertical (wall) applications, so settlement occurs over time, and you lose insulation.
The key to doing this job yourself is to determine if you can rent a high pressure blower. Purchasing such a unit seems way too expensive for a one off job. As I said, I could not find any place that would rent me one in eastern Massachusetts, not to say you can't find one where you are. Good luck with the project.
