Numerical Assessment of Indoor Air Quality in Buildings Designed with the ASHRAE 62.1 Natural Ventilation Procedure
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Date
2022-08
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The Ohio State University
Abstract
Natural ventilation is a practice typically used to cool buildings and cut energy costs by inducing airflow through building openings without involving the powered fans and controls of mechanical ventilation and cooling systems. The ASHRAE Standard 62.1-19, "Ventilation for Acceptable Indoor Air Quality," natural ventilation procedure (NVP) prescribes opening sizes as a function of occupant density and geometry for use as a ventilation strategy. Prior research documents the introduction of particles to indoor environments and health costs associated with natural ventilation as well as the decrease in its usefulness due to poor outdoor air quality. This research quantifies the IAQ impacts when implementing the Standard 62.1 natural ventilation procedure as compared to the specified mechanical prescriptive path by using coupled transient simulation between CONTAM 3.4 and EnergyPlus 9.1 over the cooling season. Three pollutant classes were identified to represent a broad range of contaminants: outdoor particles, pollutants generated indoors by human activity, and pollutants generated indoors by the building. Setting boundary conditions using TMY data for 3 representative locations along the Western Coast of the U.S., modeling found a 30% -140% increase in ventilation rates if the NVP is used over its mechanical counterpart across the geometries and occupant densities in the standard. Due to elevated ventilation rates the natural ventilation procedure reduced indoor contaminant concentrations by 11%-53% compared to the mechanical procedure. Outdoor particles, represented by PM2.5 data, averaged 25% higher concentration indoors when using the NVP as compared to mechanical ventilation with a MERV-8 filter and 667% higher compared to a mechanical system with a MERV-13 filter.
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Keywords
Natural Ventilation, Indoor Air Quality, ASHRAE 62.1-2019, PM 2.5