Inspect your garage and figure out what type of insulation is required. You will have to cater many factors in the decision making criteria; such as the size of the garage, the purpose it serve, is it attached to the house or not, and how much time you spend in your garage.
After deciding on the choice of insulating material, don your protective gear. Insulation is toxic, so it is better to cover yourself from head to toe. Measure your garage from side to side to estimate the amount of insulation required. Make sure that you measure the studs from top to bottom.
Insulation bundles comes in the form of bundles, which are composed of individual batts. The purpose of each batt is to fit in between the studs of the wall, and the most common used size for them is 92 5 /8 inch batt length.
Cross the breadth and length of the walls to get the total wall area. Insulation bundles are measured on the basis of how much area they cover, so after calculating the area of the walls you will be able to figure out the amount of insulation required for your garage.
Read the local building rules and regulations to find out any restrictions imposed on the choice of the insulating material. Take out the batts from the bundle and spread them out on the floor so that they expand to their normal size.
Put batts on the walls between the wall cavities. Get a helper to hold the batts while you fix them in their place. After covering the wall with batts put the insulation wire over the surface of the insulation in order to fix them permanently.
Repeat this process for all sides of the garage to insulate your garage completely.