The actual definition of R-Value is the capacity of an insulating material to resist heat flow. The higher the R-value, the greater the insulating power. R-Value can be important when choosing your garage door because if you are heating the garage area, you want to conserve as much heat as possible. A door with a higher R-Value will be more efficient and allow you to more effectively heat that space. There are other factors that you can look at when looking for better efficiency also—door seals, weatherstripping, and simply adjusting your door so it fits properly in the opening are a few.