On the Development and Optimization of an Urban Design Comfort Model (UDCM) on a Passive Solar Basis at Mid-Latitude Sites

Abstract

Urban climatology is a complex field owed to the intersecting parameters. In city planning, neighborhood fabric and vegetation plays a great role in modifying arid microclimates. This work presents an approach to enable urban designers to find the optimum land use parameters to achieve pedestrian thermal comfort. In this study, a model was developed based on ENVI-met simulations of two urban and suburban sites in Cairo, Egypt. Initial design parameters were; compactness degree, grass coverage, leaf area density, trees ground coverage, and asphalt and buildings areas. After regression analysis, the step-wise algorithm succeeded in creating the best fit of 94% R2 and 92% adjusted R2. The suggested Urban Design Comfort Model (UDCM) was examined using MATLAB to find the optimum design parameters. Optimum values were applied to generate primitive urban configurations using Grasshopper. The primitives were simulated again in ENVI-met to validate UDCM. The resulted value of Physiological Equivalent Temperature, PET at peak time was reduced from the initial result of ENVI-met (42.3 °C) in both sites to reach (38.7 °C) then (36.8 °C) after refinement with extra foliage. This approach, as a tool for urban designers, not only facilitates and speeds up urban form design process on a passive basis, but also provides deep insights on the development of UDCM considering all different city transects rather than two.

A Review and Insights for Eleven Years of Urban Microclimate Research Towards a New Egyptian ERA of Low Carbon, Comfortable and Energy-Efficient Housing Typologies

“…There are two main aspects that play a crucial role in modifying arid microclimates in city planning, which are the neighborhood fabric and vegetation. Yet, Fahmy et al [44] discussed other parameters affecting the arid microclimates, which are compactness degree, grass coverage, leaf area density, trees ground coverage, and asphalt and building areas. There are numerous mutual effects between built environment elements, fabric, network and vegetation that affect the microclimate change, in which these parameters should be taken into consideration when developing the urban design comfort model (UDCM) ( Figure 2).…”

“…Furthermore, urban trees possess visual, aesthetical, and psychological adaptation [79], as well as, noise reduction, and air filtering effects [80][81][82]. Moreover, the main thermal performance advantages of trees are attributed to the radiation interception and evapotranspiration effects that modifies the heat budget of surrounding air and surfaces [26,44,63,83,84]. However, that is why adaptation to climate change considers vegetation as major applications to reducing heat stresses, energy consumption and in turn carbon emissions [18,52,85].…”

“…In addition, ENVI-met has been combined with field measurements to represent Egyptian urban trees in the vegetation database through the measurements of LAI and Albedo using LAI2200c plant canopy analyzer [70] and the use of two back to back CMP21 high temperature pyranometer manufactured by Kipp & Zonnen [71] as albedometer. In the study of Fahmy et al, to develop UDCM [44], ENVI-met has been validated against both air temperature and the mean radiant temperature. This took place by comparing field measurements and ENVI-met receptor point output at the same field grid, using the Onset HOBO-U30 portable weather station [94] to measure T a , RH, and V, while the Heat Stress WBGT globe thermometer measurements [95][96][97][98] were used to measure the radiant temperature at the same grid of the receptor placed in ENVI-met Spaces modeling tool.…”

“…Due to increase in population that are expected to live in urban areas, as well as, the increase in air temperature because of the changing climate [115], it is crucial to establish an adaptive and responsive thermally efficient built environment by means of implementing passive design strategies at both building and urban scales. At the urban scale, reducing energy consumption in buildings and alleviating the urban canyon temperature is an integration of several passive design strategies such as trees [3,59,60,116], green roofs [69,73,117,118], green walls, and the fabric of local micro-climate scale [44,[119][120][121]. Based on these studies, the energy consumption of the whole examined urban forms and the housing typologies is proposed to be passively reduced through design, and the remaining energy demand can be met by renewable energy systems.…”

Mitigation strategies of the urban heat island over Greater Cairo Metropolitan Area, Egypt utilizing ENVI-met model

“…Only two greening strategies (tree lines and green roofs) were modeled. Again, Fahmy et al (2019) modeled two hypothetical cases, in new Cairo and Heliopolis, to study the combined effect of street geometry and greenery. Aboelata and Sodoudi (2019), Aboelata (2020) and Aboelata and Sodoudi (2020) simulate the effects of tree lines strategy to ameliorate microclimate conditions in cases in Cairo, and the same thing was done by Elbardisy et al (2021) Recently, Fahmy et al (2020) reviewed all the case studies on the urban microclimate of Egypt.…”