Environmental Thermal Impact Assessment of Regenerated Urban Form: A Case Study in Sheffield

Abstract

Urban comfort is becoming increasingly important due to climate change, increasing population and urbanization. Greater use of mechanical cooling is not reasonable due to consuming more energy, discharging anthropogenic heat and CO 2 emissions which all can be minimized by passive strategies. As part of the EPSRC funded project Urban River Corridors and Sustainable Living Agendas, URSULA, two radically different urban regenerations for a site in Sheffield were passively designed and had to be microclimatically assessed upon their thermal impacts. Passive design strategy for the first is wind tunneling and solar shelter effects owed to compact form that provides river bank access by perpendicular streets. The second, park option, offers space for the river to flood into a green channel which provides evaporative cooling. Simulations using ENVI-met BETA4 applied four receptors to record different meteorology and the pedestrian comfort in terms of Predicted Mean Vote, PMV. The increased green coverage showed horizontal shifting of about 0.2 with 2h of urban time lag in PMV records from 14.00-16.00LST in some places. Results give advantage for the park option design but needs more emphasize on indoor performance.

Evaluating Mitigation Effects of Urban Heat Islands in a Historical Small Center with the ENVI-Met® Climate Model

“…(Figure 4b), with the area filled with buildings clearly warmer than open and vegetated areas. The atmospheric temperature is rather homogeneous inside the old town center, with a peak of 300.2 K (27.0 °C), while the minimum temperature, again recorded in southwest green area, is 296.3 K (23.1 °C), with a difference of almost 4 K. In the main road view, small warmer spots are present, close to buildings top, caused by thermal release of roofs which is higher than that of the walls (roofs usually have higher transmittance, and in other works simulation have been carried out with this assumption [13,17,20].…”

“…The chosen area shows good presence of vegetation around the main square, while the old town center (on the right) has a typical urban canyon layout: narrow roads and tall buildings. The resolution is an average within the suggested values (minimum 0.5 m -maximum 10 m) [12][13][14][15][16][17] and is a reasonable compromise between accuracy and calculation time. A more accurate resolution would imply a larger model, taking into account that the maximum dimensions allowed by the software are 250 × 250 × 30 cells.…”

“…A typical time-space resolution of the model is 10 s/0.5-10 m [12][13][14][15][16][17]. Possible employment includes several fields, as urban climatology, architecture, building design, energetic and environmental planning.…”

Urban Heat Island (UHI) mitigating strategies: A case-based comparative analysis

“…In the specific case of ENVI-met, the main weaknesses relate to: 1) the capability of establishing relative quantities such as absolute temperature profiles and air temperature throughout the diurnal cycle (Carnielo & Zinzi, 2013;Hedquist et al, 2009;Spangenberg et al, 2008) and wind speeds (Krüger et al, 2011); 2) the inability to dynamically simulate heat storage for building walls and roofs because of constant building indoor temperatures (Chow & Brazel, 2012;Chow et al, 2011;Fahmy et al, 2011); 3) the simplification of building façades to a single, averaged heat transfer coefficient (Chow & Brazel, 2012;Spangenberg et al, 2008); 4) the lack of horizontal soil transfer within the model that potentially affects accurate calculations of soil heat storage (Chow & Brazel, 2012); and, 5) difficulties regarding interpreting pollutant dispersal results (Krüger et al, 2011).…”

Microclimate Improvement of Inner-City Urban Areas in a Mediterranean Coastal City

“…For instance, several studies have focused on: (1) investigating the Sustainability 2017, 9, 882 5 of 29 urban canyon microclimate [47,[57][58][59], (2) studying the effect of various parameters on the courtyards' microclimate, such as vegetation, paving materials, water bodies, and urban geometry [47,50,60,61], (3) studying the effect of urban morphology on the local microclimate and the human thermal comfort (calculating indexes as PMV) of various urban spaces [61][62][63][64], (4) investigating the microclimate and/or carrying out a parametric study on an urban neighborhood scale [48,54,[65][66][67], and (5) investigating the effect of green parks and vegetation on the local microclimate [49,59,68,69]. Therefore the ENVI-met reliability and accuracy as a microscale simulation model has been repeatedly proven.…”