Having enough insulation is not an "old home problem." Plenty of newer homes are lacking insulation in certain areas. One spot to consider when adding insulation is the attic. Attics are easily-accessible and many times the floor is uninsulated. The trick is determining how much is needed.
Insulation is generally measured using the term R-value. The R-value is a measure of the insulation's "thermal resistance," or resistance to heat or cold temperatures traveling through the material. The higher the R-value, the greater the product's insulating capabilities.
R-values are cumulative, so insulation can be layered to create a greater R-value. Insulation can also be combined with various types of air barriers to reduce heat transfer even further. Compressing certain types of insulation can reduce the R-value. These properties should be considered when factoring current R-vales with additional insulation.
To determine the R-value recommended for various areas of your home or business, rated for your geographic area, the U.S. Department of Energy offers the Zip Code Insulation Program. It is necessary to know the first three digits of the zip code the property is in, whether the structure is new or existing, and the fuel type used for heating.
Based on these factors, the program will suggest sufficient levels of insulation for attic, walls, ceilings and floors. For more information, visit the US Department of Energy and look for Energy Efficiency.