Cellulose attic insulation
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.