These are basic guidelines only. Every home is different, so the best way to evaluate your needs would be to conduct an in home evaluation yourself using tools such as the TVA provides or have a HEPrepresentative help.

R-value recommendations for Zip Codes in the Knoxville, TN area
Application Good Better Best
     Attic 30 38 49
     Cathedral Ceiling 30 38 38
     Wall Cavity 13 15 19
     Floor 13 19 30
     Basement Wall 11 13 15
     Crawl Space Wall 11 19 19
GOOD insulation levels will help provide basic protection from uncontrolled heat loss or heat gain through the home’s exterior, allowing standard heating and cooling equipment to maintain a comfortable inside temperature. GOOD insulation levels generally correspond to U.S. Department of Energy recommendations for homes with relatively cheap sources of heating energy, such as natural gas. These R-values often meet local building code minimum standards, although in some areas codes might call for higher levels. These R-values should be considered the bare minimum for a modern building, and higher levels might prove to be a good investment as energy costs increase.
BETTER insulation levels provide increased protection from heat loss or heat gain through the home’s exterior compared to lower insulation levels, resulting in reduced heating and cooling costs as well as a more comfortable inside environment and good sound control. BETTER insulation levels generally correspond to U.S. Department of Energy recommendations for homes with moderately priced sources of heating energy, such as heat pumps, fuel oil, or some natural gas. These R-values usually meet building code minimum standards, although even higher levels might prove to be a good long-term investment as energy costs increase.
BEST insulation levels provide excellent protection from heat loss or heat gain through the home’s exterior, meaning low heating and cooling costs compared to other insulation packages, and often allowing smaller and cheaper furnaces and air conditioners to be used. Higher insulation also results in a comfortable, even-temperature inside environment and better isolation from annoying outside noise. BEST insulation levels generally correspond to U.S. Department of Energy recommendations for homes with relatively high priced sources of heating energy, such as all-electric houses. The high R-values apply to homes with other energy sources as well, to maximize comfort and protect against future energy cost increases. These levels will meet or exceed building code minimums in essentially all areas. In most cases exceeding these levels is not a bad thing, but you will see a longer timespan for a return on your investment.Matching insulation to your structure:
A home’s structure often limits the insulation choices. For instance, 2″x 4″ framed walls will accommodate R-11, R-13, or R-15 insulation batts, but 2″x 6″ framed walls have room for R-19 or R-21 batts. (Rigid foam sheathing insulation can often be added outside the framing for additional R-value.) Likewise, a sloped cathedral style ceiling restricts the depth of insulation to R-30 or R-38 at most, while a flat ceiling with a full attic above it will have room for higher R-values of either batts or blowing wool. Ideally, the desired levels of insulation are considered during the design of the home.