Which insulation type has an R-value per inch of approximately 4?

The insulation type with an R-value per inch of approximately 4 is fiberglass batts. Fiberglass is a widely used insulation material due to its effectiveness in minimizing heat transfer. Its R-value, particularly around 3.2 to 4.0 per inch, makes it a common choice in both residential and commercial applications.

Fiberglass batts are composed of fine glass fibers, manufactured into flexible strips that can be easily cut and installed in various spaces, including walls, attics, and ceilings. The reason for its popularity lies in its relatively high thermal resistance, helping to improve energy efficiency in buildings.

In comparison, cotton batts, often made from recycled denim, have lower R-values, typically around 3.0 to 3.7 per inch. Plastic batts are less common and do not have a standardized R-value comparable to fiberglass. Mineral wool batts, while effective, generally have an R-value similar to or slightly lower than that of fiberglass.

Understanding the R-value of insulation is crucial when selecting materials for optimal energy efficiency and performance in a building's thermal envelope.