R-value rates the insulation in your garage door. The higher the R-Value, the more insulated your door. For example: The Raynor Centura Door has an 18.0 R-Value and the Clopay Premium Series 9200 Series has a 18.4 R-Value. In addition to being more sturdy, a well insulated door keeps the heat and A/C inside your home and will help keep your home at its ideal temperature. Check out this video from Clopay for more insights on choosing the correct insulation for your garage door.