In the article impact of gas interaction in sealed chambers of an insulating glass unit on load transfer between glass panes has been analysed. On the basis of the law of ideal gases a calculation model for the determination of loads on elements of a multi-chamber insulating glass unit under the action of variable climatic factors (pressure, temperature) and surface loads has been proposed. An example of unitary surface load distribution on individual glass panes has been presented as a positive influence of chamber tightness on load transfer.