There are several different factors to consider when choosing the type of attic insulation to use. You have to consider the climate you're in and which insulation will be most energy efficient there. The two basic types of attic insulation are rolled insulation and blown-in attic insulation. The most important factor to consider in a warmer climate is the addition of a radiant barrier to whichever type of insulation you select.
A radiant barrier is a material used in conjunction with attic insulation to reflect radiant heat at the surface and increase the efficiency of attic insulation. Radiant barrier is a foil that is placed between the attic floor and the insulation. Using a radiant barrier is especially important in a warmer climate because of the temperature that can be reached in the attic. The barrier foil blocks the heat during warmer weather and keeps heat in during the colder months to provide a year-round solution for energy efficiency.
Rolled insulation is more expensive than blown-in insulation, but is easier to work with because it is laid down piece by piece. Rolled-in insulation is most commonly made of fiberglass, but can be found in cotton fiber as well.
The advantages of using rolled-in insulation are that it is easy to install and easy to remove.
Blown insulation is less expensive than rolled-in insulation, but it almost always has to be installed by a professional due to the extra skill and experience necessary to operate the blowing machine. Blown-in insulation is most commonly made of fiberglass, cellulose, or rock wool.
The advantages of using blown-in insulation are that it is cheaper than rolled-in and is better able to fill small spaces.