Laminated glass is often modeled with one of various effective thickness models to simplify analysis. Effective models are intended to be limited to linear deformations however they are often employed in general glazing applications, such as windows, which typically perform nonlinearly. Consequential, window designs with laminated glass modeled with effective thickness models do not adequately represent the actual stiffness of the laminated glass lites resulting in problematic designs. In particular, insulating glass units comprised of one or more laminated glass lites may not equilibrate pressure changes do to environmental loads, e.g. wind, isobaric, thermal as intended, potentially causing premature seal failure and/or glass facture. This paper explores the differences between insulating glass units comprised of laminated glass lites analyzed with the effective thickness models and an efficient non-linear layered plate element. Several insulating glass unit constructions, including double and triples, will be explored for a wide range of rectangular dimensions, providing a comprehensive representation of the magnitude and constructions where the models agree and differ.