Cellulose is a popular type of insulation used in attics, made primarily from recycled paper products treated with fire-retardant chemicals for safety. It is typically blown into attic spaces, creating a dense, continuous layer that effectively reduces heat transfer and air infiltration. Cellulose is known for its eco-friendliness, affordability, and excellent thermal performance. Its ability to fill small gaps and cavities makes it particularly effective at improving energy efficiency in homes. However, proper installation and ventilation are essential to prevent settling or moisture retention, which could reduce its effectiveness over time.