ᐅ Thick vapor barrier instead of vapor retarder

In our insulated roof, a thick standard foil was installed years ago instead of a vapor barrier membrane. Should it be replaced?

If there is really only a standard plastic sheet instead of a vapor retarder installed, this could become a problem over time... depending on the rest of the roof construction. A simple PE (polyethylene) sheet blocks moisture too effectively, which can promote condensation within the insulation. Have you checked for any signs of moisture or dark spots anywhere?

If everything is sealed tightly and the roof can dry well to the outside, it may not need to be replaced immediately. However, without detailed knowledge of the construction, it is difficult to assess this with certainty.