Depending on house style, insulation is also required in basement, crawl space areas and at the perimeter of house slabs.
Most insulation relies on the entrapment of air in thousands of tiny pockets to be effective.
These pockets restrict the passage of heat through the insulation. In cold climates, a vapor retarder must also be used in conjunction with insulation. Without a properly placed vapor retarder, the moist hot air would soon permeate the insulating material, thereby diminishing its effectiveness. Considerations There are various types of insulation available, each with separate characteristics and insulation value. In general, the more extreme the temperature in any area, the higher the recommended R-Value.