Our client's attic was poorly insulated and had only 5 in'' of fiberglass in some places.
We seal air leaks like seams and holes to prevent the air you are heating or conditioning from escaping faster.
We blow 16" of cellulose fibers to achieve an R-60 value. It would take 22 inches to have the equivalent with fiberglass. Cellulose is therefore much more effective and efficient.