The amount of insulation recommended to be in walls depends on a number of factors such as climate, building construction, and building type.
The United States Department of Energy has developed recommended levels of insulation for various areas of the country, but for typical wood framed walls, a recommended R-value of R-13 is standard for the southern half of the United States, and an R-19 to R-21 is recommended for the northern climates.
Check local and state building codes to see what is recommended in your area.
For more information on insulating walls, visit the U.S. Department of Energy DOE Wall Insulation Tips
Also, the Department of Energy has a zip code insulation program that will calculate the most economic insulation level for your new or existing house.
Zip-Code Insulation Program
