Insulation is one of the most important parts of a home. The purpose of insulation is to slow the rate at which heat transfers. In hot climates, insulation helps to prevent the cool air from escaping to the outside and the hot air from entering into the home. It has the opposite effect in colder climates. Insulation does not directly heat or cool a space, but rather acts as a retainer or barrier to keep the desired air from escaping.