Pure XPS foam is a combustible organic material. However, for building use, flame retardant additives are incorporated during the extrusion process to meet international fire safety standards. The most common ratings are:
- Class B1 (DIN 4102) / Class E (EN 13501-1): Difficult to ignite, with limited flame spread. This is a typical requirement for building insulation in many regions.
- Class 1 (ASTM E84): Low flame spread and smoke development index.
It is crucial to always check the specific fire classification certificate for the product and ensure it complies with your local building codes. XPS should always be installed as part of a complete wall or roof assembly, which includes non-combustible coverings (gypsum board, concrete, masonry) that provide the necessary fire barrier, as required by code.
