If you're battling the elements when it comes to your garage door and leakage, there are more tools in your arsenal than just overall insulation. If wind and water find their way under the cracks of the garage door and the floor, or if you find your garage flooding often or being filled with dust and dirt from the outside, you may want to consider investing in a garage door seal.
Garage door seals easily glue or mount to the floor of your garage to create a seal like the one on your refridgerator- between the door and floor. This is particularly useful if your garage is at the bottom of a hill and prone to flooding, or if you have an uneven garage floor. Water seepage can cause a lot of damage, and a little strip of rubber can go a long way to solving the problem.
Plus, if you live in an area with pest/insect issues, the sealant will keep them out as well. A line of marching ants can't pry their way through a perfect seal.
In addition with all-over, traditional insulation, a garage door seal will also help regulate temperatures inside the garage, keeping your heating and cooling bills up.