Fiberglass insulation usually needs replacement after 15-20 years as it can become dirty, wet, moldy, and less effective.
Modern cellulose insulation is made from 75 to 85 percent recycled paper or denim, treated with boric acid, borax, or ammonium sulfate.
R21 insulation is approximately 5.5 inches thick. This type of insulation is often used in walls and provides a higher R-value compared to standard insulation options, contributing to improved energy efficiency and thermal comfort in residential and commercial buildings.