From street canyon microclimate to indoor environmental quality in naturally ventilated urban buildings: Issues and possibilities for improvement

Abstract

a b s t r a c tMany buildings in urban areas are more or less naturally ventilated. A good understanding of the current status and issues of indoor environmental quality (IEQ) in naturally ventilated urban buildings and the association with urban microclimate is fundamental for improving their IEQ. This paper reviews past studies on (a) the microclimate in urban street canyons, (b) the potential influence of such microclimate on IEQ of nearby naturally ventilated buildings, and (c) the real-life IEQ status in these buildings. The review focuses mainly on studies conducted by on-site measurements. The microclimate in urban street canyons is characterized by low wind speed, high surface temperature difference, high pollutant concentration, and high noise level. Insufficient ventilation rates and excessive penetration of outdoor pollutants are two key risks involved in naturally ventilated urban buildings. Existing knowledge suggests that reasonable urban planning and careful building envelope design are the primary methods to ensure acceptable IEQ and maximize the utilization of natural ventilation. However, quantitative studies of both microclimate in street canyons and IEQ in buildings are still highly insufficient in many aspects, which make cross comparison and influencing factors analysis currently impossible. Based on the limitations of previous studies and the current issues of naturally ventilated urban buildings, suggestions are made for future studies to better understand and improve IEQ in naturally ventilated urban buildings.

Wind tunnel analysis of flow and dispersion in cross-ventilated isolated buildings: Impact of opening positions

“…Many of these studies emerged from the SARS threat. Examples are the studies by , Niu and Tung (2008), Gao et al (2008), Ai et al (2013), Ai and Mak (2014, 2015a, 2015b and Cui et al (2016). Two review papers on the topic of inter-unit dispersion by single-sided natural ventilation were provided by Mak (2015a, 2015b) and Mao and Gao (2015).…”

CFD simulation of the effect of an upstream building on the inter-unit dispersion in a multi-story building in two wind directions

“…They found that: (a) airborne viruses have high infection rates between adjacent units in residential buildings due to the quick evaporation of Tominaga et al, 2008). These studies reveal that the presence of proximity surrounding buildings dramatically reduces the air exchange rate (ACH) and pollutant exchange rate (PCH) around buildings (Ai and Mak, 2015b;Vardoulakis et al, 2003). Among surrounding buildings, the influence of an upstream building on its downstream building was paid particular attention, as it reduces significantly the external wind speeds (Zhang and Gu, 2008;Tominaga and Stathopoulos, 2011;Chang and Meroney, 2003) and curtails the pollutant dispersion around the downstream building .…”

Improving pedestrian level low wind velocity environment in high-density cities: A general framework and case study

“…Actually, an enjoyable outdoor thermal comfort can encourage city residents to spend more time in outdoor spaces (Chen & Ng, 2012;Du, Mak, Huang, & Niu, 2017). However, congested airflow at the pedestrian level has become a major concern in the high-density cities because it is the driving force for the transfer of pollutant, heat, and water vapour (Ai & Mak, 2015;Chatzidimitriou & Yannas, 2017;Ignatius, Wong, & Jusuf, 2015). This problem is more serious in densely built cities at low or mid latitudes, such as Hong Kong and Singapore, which suffer from urban heat island and global warming Kong et al, 2017;Ng, 2009;O'Malley, Piroozfar, Farr, & Pomponi, 2015;Yang, Wong, & Jusuf, 2013).…”