Blown-in cellulose and fiberglass are typically used to insulate the walls in existing homes or areas with limited access. Batt and roll insulation is very common in new construction where access is easy. DO NOT compress insulation. Much of the value will be lost if compressed. Seal all joints and seams with quality duct tape or mastic.
Insulation is rated by R-values and expressed in terms of resistance to heat.
The higher the R-value the better the insulating power. The R-values are clearly marked on all types of insulation. Vinyl-faced insulation made especially for ducts.