This study aimed to develop a new concept for an air terminal device for a VAV (variable air volume) ventilation system that would improve overall ventilation efficiency under a varying air supply volume. In VAV systems, air volume is modified according to the thermal load in each ventilated zone. However, lowering the airflow may cause a lack of proper air distribution and lead to the degradation of hygienic conditions. To combat this phenomenon, an air terminal device with an adapting geometry to stabilize the air throw, such that it remains constant despite the changing air volume supplied through the ventilation system, was designed and studied. Simulations that were performed using the RNG k–ε model in the ANSYS Fluent application were later validated on a laboratory stand. The results of the study show that, when using the newly proposed terminal device with an adaptive geometry, it is possible to stabilize the air throw. The thermal comfort parameters such as the PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied) proved that thermal comfort was maintained in a person-occupied area regardless of changing airflow though the ventilation system.

The article presents results of long-term experimental study of hygrothermal performance of envelope assemblies in a passive house located in Boruszowice (Southern Poland). The building was constructed in 2010 using prefabricated, lightweight technology. The construction of the walls and roof had been carefully planned to test both traditional solutions with higher thermal insulation and modified ones to improve the hygrothermal performance. Altogether, eight different walls and two roof constructions were integrated into the building structure and tested from the beginning of 2011 to the end of 2015 under real climate and usage conditions. In all assemblies, temperature was measured in three and relative humidity in four points at the surface and inside. Inner climate was measured by thermohygrometers installed in the rooms and outer climate was recorded by a weather station located near the building. Theoretical calculations were made using WUFI^® Plus software. Based on experimental and calculation results, the main hygrothermal phenomena depending on construction specifics and used materials are presented.