Air cycles in the built environment: towards a bioremediation building envelope system for improved air quality

Abstract

According to the World Health Organization and the European Environment Agency, air pollution is the biggest environmental health risk today. Although general pollutant levels have improved in the last few decades, it is only recently that certain types of highly toxic human-made pollutants have been emitted in unprecedented quantities, primarily in developing regions. Moreover, within these geographic regions, the global population is estimated to double by 2050. The climatic context in most of these predominantly unindustrialized economic territories favors natural ventilation and the seamless interaction between indoor and outdoor spaces. Still, these areas mainly rely on mechanical systems to homogenize atmospheric living standards. Air conditioning systems produce wasted heat that alters the microclimate of buildings' surroundings while creating additional air pollution exhausted by the running cycles of equipment. To disrupt this cycle of energy expenditure and air pollution replenishment, this research proposes a hybrid air purification modular ceramic system for building envelopes in regions where fiscal means are limited, and natural ventilation is a viable option, in order to regulate both exterior and interior atmospheric pollution. This infrastructural strategy serves as a site of inquiry towards the potential amelioration of local urban pollution airstreams in the developing world. Contrary to the majority of existing phytoremediative systems, which perform as extensions of mechanical automated systems, the proposed approach aims to redefine the function of the building envelope as a mediating boundary layer in environments conducive to natural ventilation. It represents the first of its kind system to suggest the use of potentially passive bioremediation systems as a mediator of indoor and outdoor air. The objective is to create a low-tech, high-value system, conceptualized as a combination of mechanical components, with the effectiveness and sensitivity of biological organisms. Nevertheless, rather than a specific design and development proposal, this thesis establishes a framework for multivariant evaluation of air pollution and the ways in which it may be remediated by novel phytoremediative building enclosures. While multiple variables affect phytoremediation potential, airflow was identified as the driver of mass and energy exchange. Pressure and airflow properties of a novel envelope system's module were studied as part of simulations using Computational Fluid Dynamics (CFD), which proved itself a valuable tool to characterize airflow properties, opening new experimental opportunities for air filtration technology development. The CFD simulations was part of the process of defining the framework of this new envelope biofiltration system that regulates air pollutant removal in spaces designed for natural ventilation. Although with this work the technical applicability of the most optimized prototype version has been established for the proposed system (AMPc), the intention was not only to provide an explicit technical solution, but also to suggest an encounter with cultural settings, based on the premise that when people lose their relationship with the environment due to air pollution, they also lose their societal cohabitation and cohesion patterns.