Study on the conversion coefficient between ACH50 and ACH in typical zones of public buildings

Abstract

• Analyzed the conversion coefficient (CC) between ACH 50 and ACH of public buildings. • CC is strongly affected by meteorological conditions and varies in a wide range. • Recommended value of CC was given, as well as the applicable condition. The air infiltration of buildings is closely related to its indoor and outdoor environment and energy consumption. However, measuring air infiltration of a building under natural conditions is time-consuming, easily affected and expensive, so it's often inferred based on building airtightness in practical engineering. Empirical models can nevertheless make a rapid prediction without building parameters, which are widely applied in practical engineering. At present, most of the existing empirical models take residential buildings as objects, therefore they are difficult to be applied to public buildings. Hence, it is imperative to build an empirical model applicable to public buildings. In this study, the conversion coefficients between the airtightness (air change rate under the pressure difference of 50Pa) and the air infiltration rates under natural conditions of four typical zones of public buildings were analyzed. Firstly, the airtightness of four zones of public buildings in the cold region of China was measured. Secondly, their air infiltration rates under 1800 combined conditions of wind pressure and stack effect pressure were simulated based on the airtightness measured results. Finally, calculation and statistical analysis of the conversion coefficient were carried out based on the measured and simulated results, and the recommended value of conversion coefficient was proposed. Analysis results show that the CC of each zone is significantly affected by outdoor meteorological conditions and varies in a wide range (1# zone: 3.21 to 188.44). It is advised to ignore the extreme data and take the mean value of the CC corresponding to 95% of the data volume as the recommended value (22.2). This study can provide theoretical basis for the formulation of standards for the performance evaluation of building airtightness.