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Impact of ventilation: creating a healthy indoor environment by understanding the impact of ventilation on indoor air quality in commercial buildings
Dissertation   Open access

Impact of ventilation: creating a healthy indoor environment by understanding the impact of ventilation on indoor air quality in commercial buildings

Tom Ben-David
Doctor of Philosophy (Ph.D.), Drexel University
May 2018
DOI:
https://doi.org/10.17918/etd-7958
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Abstract

Building Energy consumption--Simulation methods Heating and ventilation industry Indoor air quality
Ventilation plays a significant part in building dynamics, affecting building energy consumption and indoor air quality (IAQ) in complex and often conflicting ways. Ventilation standards often prescribe minimum ventilation rates (VRs) in a one-size-fits-all manner that ignores the unique impact ventilation has on different buildings. This Thesis investigates the existing knowledge of ventilation outcomes to develop a customizable ventilation control strategy that would result in specific, predicted ventilation outcomes. The ways in which ventilation may affect building energy use and IAQ were explored through a literature review and three research objectives were established to develop this strategy. The first objective included an exploration of the impact that ventilation has on the indoor concentration of atmospheric contaminants. While ventilation can introduce these harmful pollutants indoors, the most potent of which (particulate matter) can be much more effectively controlled by improved filtration. It was further shown that filtration becomes more efficacious that higher VRs. The second objective was designed to create a methodology that would allow one to optimize daily VRs based on desired outcomes. This was done by constraining energy cost to levels currently achieved using an existing ventilation strategy and optimizing positive IAQ outcomes of introducing more outdoor air-which is generally considered cleaner than indoor air-indoors based on building parameters, climate, and user preferences. Thus, the premise of this ventilation strategy was to improve IAQ to a theoretical optimum by introducing more fresh air indoors at no additional energy cost. Potential ventilation outcomes were shown on a Pareto frontier that represents a tradeoff between energy use and IAQ. Pareto optimized VRs were shown to be weather dependent, and a method to generate predictive models to estimate optimal ventilation based on outdoor conditions was developed. In the third objective, a control scheme was developed to implement the proposed ventilation strategy in real buildings using a CO₂-based demand-controlled ventilation approach. This optimization and control scheme was implemented in a virtual testbed emulating ventilation control in a real building. Overall, ventilation was successfully maintained at target levels, except for when very low VRs were desired, where damper leakiness, infiltration, and CO₂'s slow buildup indoors impeded proper control. An analysis of the implementation this ventilation strategy over the entire small-to-medium-large U.S. office sector found that it can improve occupant productivity by improving IAQ by 1.3% on average, or an equivalent $50 billion of potential benefit for the entire sector, while only increasing energy cost by 1% or $0.1 billion for the entire sector.

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