Interzonal air and moisture transport through large horizontal openings in a full-scale two-story test-hut: Part 1 – Experimental study

Moisture transport by convection through large horizontal openings in dwellings, such as staircases, could have significant impact on the level, variation and distribution of humidity in each zone of dwellings. Yet, most studies and simulation tools of heat, air and moisture transport in buildings do not consider nor properly model this phenomenon; the lack of experimental data is one of the main causes. The aim of this experimental investigation was to study the air and moisture transport through a horizontal opening in a full-scale two-story test-hut. This study extended the cases with buoyancy-driven flows that have been studied by a handful of existing investigations, to the cases of combined buoyancy airflows and mechanical ventilation and cases with warmer upper room than the lower rooms. The main investigated parameters were different ventilation strategies, ventilation rates, and temperature differences between the lower and upper rooms. In total, 20 cases were tested. Measurements of temperature, relative humidity and air velocity were carried out within both rooms and across the horizontal opening. The air and moisture exchange through the horizontal openings are investigated based on two quantities representing the phenomenon: (i) steady-state difference between the average humidity ratios of the two rooms at the end of the moisture generation period, and (ii) mass airflow rates through the opening. The results show that interzonal air and moisture exchanges through the horizontal openings are strongly linked to the temperature difference between the two rooms, and the mechanical ventilation significantly restricts the interzonal airflows in comparison with cases without mechanical ventilation.