Assessing the Impact of Natural Ventilation on Indoor Air Quality in Residential Buildings

Thesis Abstract

The quality of indoor air substantially influences occupants’ health and comfort, especially in residential environments where individuals spend a significant portion of their daily lives. Despite increasing awareness of the importance of natural ventilation as a sustainable and cost-effective strategy for improving indoor air quality (IAQ), there remains limited empirical data quantifying its real-world effectiveness across diverse residential settings. This study aims to assess the impact of natural ventilation on IAQ in residential buildings, with specific objectives to quantify ventilation rates, identify prevalent indoor air pollutants, and determine the relationship between natural ventilation practices and IAQ parameters. The research adopts a mixed-methods approach, combining quantitative field measurements with qualitative occupant surveys to generate comprehensive insights into ventilation behaviors and IAQ dynamics. A cross-sectional research design is employed, targeting residential buildings within a metropolitan area characterized by varied climatic conditions and building typologies. The population comprises 150 randomly selected dwellings representing different architectural styles and occupancy patterns. A stratified random sampling technique was utilized to ensure representation across socio-economic strata. Data collection involves deploying portable air quality monitors to measure concentrations of key indoor pollutants, including particulate matter (PM2.5 and PM10), carbon dioxide (CO2), volatile organic compounds (VOCs), and formaldehyde, over a continuous period of seven days in each dwelling. Ventilation rates are calculated using CO2 decay methods, complemented by occupant surveys that capture self-reported ventilation practices, window-opening frequency, and perceived IAQ satisfaction. To validate the measurement instruments, reliability testing is conducted through repeated measures and calibration against reference standards, while validity is ensured via pilot testing and expert review. Qualitative data from occupant surveys are analyzed thematically to contextualize quantitative findings. The primary analytical techniques include multiple regression analysis to examine the influence of natural ventilation variables on IAQ parameters, ANOVA tests to compare pollutant concentrations across different building types and ventilation strategies, and structural equation modeling to explore complex relationships among variables. The theoretical underpinning draws on the Environmental Behavior Theory and the Ventilation Control Model, providing a framework to understand how occupant behaviors influence IAQ outcomes through ventilation practices. It is anticipated that the findings will demonstrate a significant inverse relationship between effective natural ventilation and indoor pollutant concentrations, with buildings exhibiting higher window-opening frequencies showing markedly lower levels of PM, CO2, and VOCs. The study further expects to identify critical thresholds of ventilation rates necessary to maintain IAQ within national and international standards. A comparative analysis indicates that buildings with passive ventilation strategies outperform mechanically ventilated counterparts in sustaining better IAQ, particularly in temperate climatic zones. This research contributes to existing knowledge by providing empirical data on the efficacy of natural ventilation in residential contexts, elucidating behavioral factors influencing IAQ, and proposing practical guidelines for optimizing natural ventilation for health and sustainability. The main conclusion underscores the importance of promoting occupant awareness and behavioral interventions alongside design strategies to enhance natural ventilation performance. Recommendations include integrating passive ventilation design features in new constructions, developing occupant education programs on ventilation practices, and establishing regulatory standards tailored to natural ventilation conditions. Future studies are suggested to explore long-term health outcomes associated with natural ventilation-driven IAQ improvements and to validate findings across different geographic regions. The findings aim to inform policy, architectural design, and public health initiatives aimed at improving indoor environmental quality in residential buildings globally.