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1. Introduction
The success of moisture- and mold-damaged building repairs depends on many factors. Reaching a consensus about the necessary repair methods and schedule is not always simple, and the response to problems might therefore be delayed. Occupants’ symptoms and discomfort can have multiple causes, and detecting or treating them all is not always possible nor successful [1]. In cases where harmful impurities remain in the structures or crawlspaces after repairs, indoor air problems might still occur. It has been shown that negative pressure indoors may introduce harmful pollutants [2], e.g., fungal spores [3], which may cause adverse health effects among occupants [4]. Preventing infiltration of the possible impurities from the structures or surroundings, caused by high negative pressure, is crucial for maintaining a good indoor air quality (IAQ). In moisture damage repairs, a thorough renovation, including ventilation, is important [5].
Ventilation is strongly associated with perceived IAQ, health, and productivity [2,6]. The chosen ventilation strategy also significantly affects the indoor microbial community [7]. Indoor fungi can be useful indicators of IAQ, therefore a deeper understanding of their biology is of special importance [8]. Ventilation, as well as indoor temperature and humidity, have a significant impact on human perceptions and well-being [9,10]. Proper ventilation measurements should be an essential part of every IAQ investigation [11]. In air-tight buildings with a mechanical ventilation system, the balancing and controlling of the ventilation system and pressure differences are inevitable [12]. When evaluating the effect of ventilation on perceived IAQ, pressure difference measurements are important [13].
In cold-climate countries, keeping structures dry is a main issue, and ventilation design is strongly related to this objective. According to the National Building Code of Finland [14], pressure conditions should not generate moisture loads on structures and, at the same time, not assist pollutant transfer through the structures. A ventilation design is typically balanced, or the extract airflow rate is slightly higher than the supply, to prevent exfiltration of moist indoor air into the structures. However, in well-ventilated buildings, the indoor air is often dry, and school buildings are typically occupied only during normal office hours. In such buildings, the risk for condensation is improbable despite the pressure conditions.
This ventilation intervention study was conducted as part of the Finnish EURA- and...