Generally, XPS insulation doesn’t require a separate vapour barrier. This is due to its closed-cell structure, which naturally provides a degree of moisture resistance. The need for an additional vapour barrier can, however, depend on the specific conditions of your building project, such as the location of installation and the overall design of the building envelope.

It’s always a good idea to assess the individual requirements of your construction or renovation project. If you’re unsure whether a vapour barrier is needed with XPS insulation in your specific situation, we recommend consulting with an expert.