Which type of backing is common in paper-backed insulation?

The correct choice is Kraft, which is indeed a common type of backing used in paper-backed insulation. Kraft paper is favored due to its strength and durability, providing a reliable protective surface that also allows for some breathability. This quality is essential in insulation applications, as it helps manage moisture while still providing effective insulation.

Kraft paper also has a natural resistance to moisture, making it suitable for various climates and conditions. It is biodegradable and often used for eco-friendly insulation products. The choice of Kraft as a backing material can significantly contribute to the insulation's overall effectiveness in energy efficiency and thermal performance.

Foil and plastic, while used in their own insulation products, do not provide the same balance of durability and breathability that Kraft offers, and they serve different purposes in insulation systems. Therefore, Kraft is the appropriate and commonly used backing material in paper-backed insulation.