The amount of insulation found in a garage door can have not only a dramatic effect on the temperature of your garage but on the temperature of neighboring rooms.  The amount of insulation that a garage door provides is represented by an international measurement called the R-value.  It is important to select a garage door with an R-value that is consistent with how you intend to use your garage.  Do you heat or cool your garage? Well, insulation will prove very important.  A well-insulated garage door will help maintain/regulate temperature while keeping your heating or cooling costs down.  People who enjoy working in their garages may want their garage to be more insulated. If your garage is attached to your house, the insulation value of your garage door affects the insulation of your whole house.