##ABOUT BLOWN-IN OR LOOSE-FILL INSULATION
Typical wall and ceiling cavities aren’t uniform in size; some are 22 1/2 in. wide, while others are narrow. They can include electrical boxes, wiring, plumbing vents, and blocking. Because of these variations, it’s hard to get batt insulation to conform to all the voids in a stud or joist bay.
In contrast, blown-in insulation provides better performance than batts by filling odd-shaped cavities completely.