Unhealthy indoor humidity levels associated with ventilation rate regulations for high-performance buildings in China

Abstract

Traditionally, minimum ventilation rates (VRs) have been determined based on perceived air quality, as well as on energy and economic considerations. Recently, increased attention has been paid to health-based VRs, which emphasize the health benefits and consequences associated with pre-determined VRs. In China, higher indoor air quality (IAQ) and healthier indoor environments are in great demand as high-performance buildings (HPBs), such as "nearly zero-energy buildings", are emerging. These buildings feature higher airtightness to reduce infiltration and improve energy efficiency, whereas the additional impact on IAQ is unclear. In this study, we examined the VR regulations for HPBs from a long-overlooked, infiltration-contributed and occupant-health-correlated perspective, i.e., indoor humidity. More than 4600 building models for both residential and office HPBs in five climate zones of China were simulated, by considering occupant schedules, using EnergyPlus, as well as regular buildings for comparison. The method was validated by two sets of data, i.e., one from literature, the other from a field study. Risk of high humidity (RHH) was proposed for assessing the health risk from the indoor humidity environment, as associated with the recommended VRs. Main conclusions included, first, small-sized and some medium-sized residential HPBs in southern China had a risk of high humidity that complied with current VR regulations (approximately 8 L/s) in the Chinese standard. Second, office HPBs had little high-humidity risk under the current regulations. Third, a single design factor may double the RHH. Finally, HPBs with mandated VRs were less prone to high humidity as compared to regular buildings.