In the structure of insulating glass units (IGUs) there are gas-filled gaps. Therefore, changes in atmospheric pressure and temperature, as well as the action of wind, result in a load on the component glass panes. However, the deflection of the panes connected with climatic loads results in an interaction of the gas closed in the gaps, which partially reduces climatic influences. The aim of this article is to analyze the influence of IGUs dimensions on the maximum stresses and deflections in the component glass panes, also in the context of the use of multi-glazed IGUs. Three typical loads were analyzed. It was found that in the case of wind load, with increasing dimensions of the IGUs, the stresses and deflections increase. On the other hand, in the case of loads related to pressure and temperature changes, in large-size IGUs, the gas interaction in the gaps is significant, which reduces the resultant load on the panes. It has been shown that there are critical IGU dimensions here for which the stress and deformation ratio are greatest. It was also found that increasing the number of gaps in IGUs results in a significant increase in the stress and de-flection values due to climatic loads.