Which insulation material is flammable and used as a vapour barrier?

Polyurethane is indeed an insulation material that is flammable and often serves as a vapor barrier. It is commonly used in construction due to its high thermal resistance and ability to be formed into various shapes and sizes, making it versatile for different applications. Polyurethane can be found in both rigid and flexible forms, with rigid polyurethane foam being particularly effective for insulation purposes, especially in walls, roofs, and under slabs.

As a vapor barrier, polyurethane acts to prevent moisture vapor from passing through the insulation, which is crucial in maintaining energy efficiency and preventing mold growth within building assemblies. However, it is important to handle this material with caution due to its flammable nature, especially during installation or if exposed to high temperatures.

This characteristic of being both flammable and used as a vapor barrier distinguishes polyurethane from the other options. Cellular glass, mineral wool, and vermiculite, on the other hand, are generally non-combustible or fire-resistant materials and do not typically serve as vapor barriers in the same way polyurethane does.