Quantifying the Impact of Traffic-Related Air Pollution on the Indoor Air Quality of a Naturally Ventilated Building

Natural ventilation strategies may deteriorate indoor air quality when in close proximity to roadways, although the intention is often to reduce energy consumption. In this study, we employed a CFD-based air quality model to quantify the impact of traffic-related air pollution on the indoor air quality of a naturally ventilated building in a near-road environment. The model performance is evaluated and adequately agrees with the PIV measurement on a cross-ventilated building model. Our study found that the building envelope restricts dispersion and dilution of particulate matter. The indoor concentration in the baseline condition located 10m away from the roadway is roughly 16-21% greater than at the edge of the roadway. The indoor flow recirculation creates a well-mixed zone with little variation in fine particle concentration (i.e., 253 nm). For ultrafine particles (<100 nm), a noticeable decrease in particle concentrations indoors with increasing distance from the road is observed due to Brownian and turbulent diffusion. In addition, the indoor concentration strongly depends on the distance between the roadway and the building, particle size, wind condition, and window size and location. A break-even point is observed at D'~2.1 (normalized distance from the roadway by the width of the road). The indoor particle concentration is greater than that at the highway where D'<2.1, and vice versa. Regarding the impact of window opening size, increasing the window opening enhances cross-ventilation and reduces the indoor concentration as a result. Our analysis also suggests that the indoor air quality can be considerably improved (22.5-50% particle concentration reduction) by naturally drawing air from less contaminated sides of the building. For new building planning, the distance from the roadway and the ambient wind condition need to be considered at the early design stage whereas the size and location of the window openings, the layout of interior space, and the placement of fresh air intakes are important factors to the indoor air quality of existing buildings adjacent to roadways.