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SPATIOTEMPORAL MAPPING OF CARBON DIOXIDE CONCENTRATIONS AND FLUXES IN A MECHANICAL VENTILATION SYSTEM OF A LIVING LABORATORY OFFICE
Indoor air quality in office buildings can impact the health, well-being, and productivity of occupants. In most buildings, occupants exhaled breath is the primary source of carbon dioxide (CO2). Concentrations of indoor CO2 are also strongly associated with the operational mode of the mechanical ventilation system. While CO2 is routinely monitored in indoor environments, there are few spatially-resolved real-time measurements of CO2 throughout mechanical ventilation systems. Such measurements can provide insight into indoor- and outdoor-generated CO2 dispersion throughout a building and between the building and the outdoor atmosphere. This thesis aims to investigate spatiotemporal variations in CO2 concentrations and mass fluxes throughout a mechanical ventilation system of a living laboratory office in a LEED-certified building. The impact of human occupancy patterns and ventilation conditions of CO2 concentrations and fluxes was evaluated.
A four-month measurement campaign was conducted in one of the four living laboratory offices at the Ray W. Herrick Laboratories. The living laboratory offices feature precise control and monitoring of the mechanical ventilation system via an advanced building automation system. Various mechanical ventilation modes were implemented, such as variable outdoor air exchange rates (AERs) and recirculation ratios. A novel multi-location sampling manifold was used to measure CO2 at eight locations throughout the ventilation system, such as across the outdoor, supply, and return air ducts. Office occupancy was measured via a chair-based temperature sensor array. Volumetric airflow rate data and CO2 concentration data were used to estimate CO2 mass fluxes through the ventilation system. The CO2 mass flux for the outdoor and exhaust air was used to evaluate the net CO2 transport from the office to the outdoor atmosphere.
The measurements demonstrate that there exist significant spatiotemporal variations in CO2 concentrations across the outdoor, supply, and return air ducts. CO2 concentrations varied with human occupancy in the office and the outdoor AER of the mechanical ventilation system. Due to human-associated CO2 emissions, the net CO2 mass flux from the office to the outdoor environment was approximately 700 kg of CO2 per year. Thus, occupied offices may represent an important, yet unrecognized, source of CO2 to the urban atmosphere.
- Master of Science in Engineering
- Environmental and Ecological Engineering
- West Lafayette