Green building is the practice of creating structures that are energy and cost efficient, and insulation is one of the major elements that help a building to achieve these efficiencies. Home insulation is green by its very nature because it saves energy. Reducing the energy costs is one of the most important criteria in selecting insulation. Insulation is used to keep the warm air in for cold weather. In case of warm weather, it keeps the hot air out. The overall energy performance of a building is significantly affected by issues associated with insulation system.