Yes. Theoretically, if it were possible to achieve 100% surface contact with rFOIL and the metal exterior, the performance of rFOIL could be compromised.
However, two factors prevent this from ever occurring in metal building installations. First, the natural weight of rFOIL makes it easy to achieve the necessary drape to ensure optimum performance. When pulled tightly during installation, rFOIL will naturally drape 2 ½” when spanning purlins spaced 5’ on center. Second, the ribbed profile of exterior metal adds to the airspace already in place.
Also, rFOIL provides a thermal break where the exterior metal attaches to the purlins. The only conductive transfer that occurs is via the screws that attach the exterior metal to the purlins.