The insulation requirements for homes vary based on the location of the home, but in the United States, most homes should have attic insulation equal to values between R-30 and R-60. Local building codes determine the minimum insulation value but additional insulation makes the home more efficient.
Building codes also specify the R-value for insulating walls and floors. During the installation process, the installer should not crush the material to fit into a cavity or around a pipe. He should cut it to fit the opening or so there are flaps in front of and on the sides and back of pipes.
Manufacturers measure insulation R-values based on the material's resistance to heat transfer. The manufacturer and type of insulation determine the number of inches of insulation needed to achieve the R-value. While local building codes only apply to new construction and remodels when the house is subject to inspection, increasing the insulation to match these values is beneficial to owners of older homes, too.
The most cost-efficient time to insulate a home is during its construction. However, it is possible to retrofit materials into existing homes. Anytime an owner removes a wall panel for other work, he can fill the cavity with the appropriate R-value. Other options include cutting holes into the walls and using a machine to blow in more materials.