Assessment of in-situ aging and maintenance impact on Relative Humidity-Controlled Mechanical Extract Ventilation (RH-MEV) Systems: A Case study in multi-family social housing buildings

This paper presents a comprehensive evaluation of Relative Humidity-Controlled Mechanical Extract Ventilation (RH-MEV) systems installed in multi-family social housing buildings, focusing on the assessment of in-situ aging and the impact of maintenance on the performance of the system. Building upon the Performance 2 project conducted from 2020 to 2024, which evaluated the durability and performance of RH-MEV systems over a 15-year period, this study delves deeper into the longevity and maintenance aspects of these systems. The research investigates the performance of provisory products, both inlet and extract units, after 1.25 years of operation under real conditions. Provisory units were installed and operate during the performance characterization in the lab after 13 years of in-situ operation of the real products between Performance 1 and Performance 2 projects. The performance of provisory products after 1.25 years of in-situ operation is compared to the manufacturer’s specifications, highlighting the impact of factors such as aging and maintenance. Furthermore, the study examines the influence of maintenance on the performance of the system by comparing the results of the characterization of the provisory ventilation units as collected after 1.25 years of operation (dirty) and after cleaning (as could be done by the occupant), against the original manufacturer tolerances. The findings reveal significant variations in cleanliness among different types of ventilation units. Kitchen exhaust units were found to be the most heavily soiled, with oily residues, while some bathroom and shower room exhaust units appeared more encrusted with a mixture of dust and fibres. Despite these cleanliness challenges, the hygroscopic function of the units remains intact, allowing them to modulate ventilation rates based on humidity levels. However, airflow limitations were observed at low humidity levels in both kitchen and bathroom/shower room exhaust units. In contrast, air inlet units were generally cleaner and exhibited a positive response to changes in humidity levels, confirming their functionality in modulating airflow based on indoor conditions. Overall, most of the ventilation units met fabrication specifications, ensuring optimal operation despite the state of cleanliness, and guarantying the Indoor Air Quality (IAQ) in the housing buildings after 1.25 years. This analysis provides insights into the need of maintenance procedures in sustaining or enhancing the performance of RH-MEV systems over time. The paper discusses the implications of in-situ aging and maintenance on RH-MEV system performance, providing valuable insights for system designers, manufacturers, and building managers. By understanding how these factors affect long-term performance, stakeholders can make informed decisions regarding system design, maintenance schedules, and IAQ management strategies, ultimately enhancing IAQ and occupant comfort in multi-family social housing buildings.