Loose-fill or batt insulation is typically installed in an attic. Loose-fill insulation is usually less expensive to install than batt insulation, and provides better coverage when installed properly.
To find out if you have enough attic insulation, measure the thickness of the insulation. If it is less than R-30 (11 inches of fiberglass or rock wool or 8 inches of cellulose), you could probably benefit by adding more. Before insulating, seal any air leaks and make roof and other necessary repairs. If it is located in a conditioned part of the house, also remember to insulate and air seal your attic access.