The study describes an experimental study of buoyancy-driven Row between lower and upper compartments of a stairwell model with through-flow via two small openings, one as the inlet located in the lower compartment and the other as the outlet, in the upper compartment. The driving force for the Row is the energy input from a heater located in the lower compartment. The emphasis of the paper is on the effect of the outlet size on the fluid Row and energy transfer between the two compartments and on the heat losses from the stairwell to the surrounding. The velocity and temperature profiles at various cross sections of the stairwell are presented and discussed. The results also include the gross parameters of the Row such as the mass flow rates of the upflow and downflow and the effects of the opening size on them. The results show significant influence of the opening size on the fluid Row and energy transfers within the stairwell.