Blown-in cellulose insulation is insulation bits or pellets that an installer uses a large hose to blast or spray onto walls, attics and floors. Outside, a massive machine churns the chunks and utilizes air to blast them through the hose. Blown-in cellulose insulation consists of newsprint, cardboard, office paper reclaimed or recycled and is treated with a fire retardant. The R-value varies from 3 to 4 per inch of cellulose insulation.
For any form of remodeling where walls are being opened up and for attics with open joists containing wiring, plumbing, venting, etc., blown-in cellulose insulation is the option. Blown-in cellulose insulation can work better and more fully in the areas around any barriers and areas that are difficult to access.
Blown-in cellulose insulation is a compound that a specialist would do because it needs special equipment to be built and is not recommended by the Do-It-Yourself-er 'to do so. It is less likely to find moisture seeping in there with blown-in insulation and no chance that rodents can find their way through it.

Although blown-in insulation is typically more costly, it can be installed quicker and more effectively than 'batt and roll' insulation, which involves removal of the wall rather than just a hole that needs to be filled upon completion. So it can be reasonably equal in terms of cost, taking into account the complexity of the entire project.