Currently ASTM E1300-16 is only applicable to insulating glass units (IGUs) with four-sided edge support. For potential design or forensic use (e.g., where loss of structural silicone support has occurred), the authors used a modified ASTM analytical procedure to determine the load resistance of rectangular double IGUs supported along two parallel edges. The Analytical Procedure of ASTM E1300 was utilized with several significant enhancements, including finite element modeling of a rectangular plate simply supported on two parallel edges and partially supported on the other parallel edges (owing to the spacer stiffness), application of the Muir and Walker’s glass failure prediction model for glass edges along the partially supported edges of heat treated glass, and a load sharing model based on the ideal gas law and the partially supported edges. Residual compressive surface stress of the heat-treated lites were assumed to be the minimums specified in ASTM C1048-12. An iterative analysis procedure was used to converge on an applied uniform pressure corresponding to a maximum probability of breakage of 8 lites per 1000. This paper will explore sample double IGUs with asymmetrical constructions analyzed for positive and negative pressure to simulate wind loads.