Interlayer modulus influences the stress laminated glass experiences under load. The determination of interlayer modulus data is fairly complex, and the design engineer would rely in most cases on interlayer modulus properties as determined on the foil, as published by the interlayer producers. For a structural PVB type interlayer, the modulus values of the interlayer as expressed in laminated glass, have now been determined using torsional glass laminate (360 * 1100 mm) testing. Load cases at 0 °C, 23 °C and 40 °C have been studied for durations up to one month, covering many conventional load scenarios as experienced by buildings. In addition, allowable modulus values for design for this PVB type have become available through a recent German national approval for fixed load scenarios, and more flexibly for other load scenarios, through a Prony-series approach. This paper aims to present the different type of modulus data that have recently become available in terms of conventional load scenarios, and analyze the effect of different modulus data sources on effective thickness. This allows the design engineer to make a better informed choice around modulus data used for modeling, and choose values as appropriate for specific project design.