The type of insulation you use will be determined by the nature of the spaces in the house that you plan to insulate. For example, since you cannot conveniently "pour" insulation into an overhead space, blankets, spray or board products, or reflective systems are used between the joists of an unfinished basement ceiling.

The most economical way to fill closed cavities in finished walls is with blown-in insulation applied with pneumatic equipment or with foamed-in-place polyurethane foam.

It is important to know that the different forms of insulation can be used together. For example, you can add batt or roll insulation over loose-fill insulation, or vice-versa. Usually, material of higher density should not be placed on top of lower density insulation that is easily compressed. Doing so will reduce the thickness of the material underneath and thereby lower its R-value.

In cold climates, some low-density loose-fill insulation allows air to circulate between the top of your ceiling and the attic. This air circulation can decrease the effective thermal resistance of the insulation and may be significant.  You can eliminate this air circulation by covering the loose-fill insulation with a blanket insulation product or with a higher density loose-fill insulation.

Whatever insulation you decide to purchase check the label to make sure that it is right for the application you have in mind. A good insulation label should have a clearly stated R-value, and information about health and safety issues. Such as

• Insulation material type
• R-value of the insulation 
• Outline of typical uses 
• Safety precautions in application 
• Square foot of coverage per package