Preliminary Discussions on Effects of Ventilation Rates on Moist-related Issues for Residential and Office Buildings in China

摘要

Ventilation is the most common method to dilute indoor air pollutants in buildings. In practice, what the adequate ventilation rate for a specific building space should be is often of interest to many and applicable to debates. During the last ～200 years, the recommended ventilation rates are determined mostly based on bio-effluents (e.g., C02, etc.) that may cause discomfort or odor, rather than concrete health-based evidences. At present, health requirements have raised more attention and in the Europe, 4 L/s has been proposed to be the minimum ventilation rate per person that prevent occupants from suffering unaccepted health consequences. In this paper, a preliminary discussion on methods to determine ventilation rate based on one aspect of the health requirements, i.e., humidity environment and habitability of microbes, is presented. Both residential (natural ventilation) and office (mechanical ventilation) settings have been included in the scenarios and meteorological data from 5 cities, that each has been selected to represent one climate zone in China. Two generally-agreed relative humidity levels, i.e., 1) 30%; and 2) 60% are adopted as the low and high thresholds, respectively, to, 1) reduce health symptoms, such as dry eye and irritation; ) reduce the proliferation of house dust mites, as well as the emergence and development of molds, respectively. The results showed that, first, for offices, the mechanical ventilation strategies should be closely corresponding to the occupation patterns. Second, for residences, although mechanical ventilation is not widely used in China, an equivalent 4 L/s of natural ventilation may not be sufficient for regions that have higher outdoor humidity levels, suggesting that dehumidification is needed. Third, infiltration plays a surprising and sometimes unwanted role in controlling indoor humidity level. When building airtightness is not good, a revised ventilation rate based on climate conditions would be required.