You can save money on energy by using insulation for your house. One of the best materials for insulation is cellulose. It is very cost effective and quite cheap.
The R-value refers to the resistance of heat transfer or the insulator. higher values mean a better insulation. Cellulose usually has a value slightly over 3. Consider the climate when you go shopping as it can influence the R-value a lot.
Search on the internet for the best R-value for your climate zone. Once you have found it divide it by 3 and thus you will get the thickness of the cellulose insulation, measured in inches. For example if the R-value is 3, the layer needs to be 1 inch thick.