Roof renovation from outside - Pavatex

The company Pavatex (as well as other manufacturers of wood fiber insulation materials) offers a renovation solution for roofs that does not require the use of a vapor barrier foil. Only the room-side cladding must have a certain degree of vapor-retarding function. The airtightness of the system is ensured by installing a special highly diffusion-open foil (0.02), which is laid flat over the rafters (that is, above the between-rafter insulation, which consists of wood fiber softboards). Above this airtight foil, an insulation layer of at least 35 mm wood fiber boards must then be applied. According to the manufacturer, the wood fiber insulation materials are so diffusion-open that any moisture that may occur is quickly transported outward. Pavatex argues that this construction is more fault-tolerant than a conventional setup with the installation of a vapor barrier foil in a valley-and-ridge method, as this cannot be carried out cleanly in old buildings. Are there any practical experiences with this?

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