Urban Geometry, SVF and Insolation of Open Spaces: the case of London and Paris

The radiant environment in open spaces is very sensitive to the surrounding built form, which determines their openness to the sky and exposure to the sun. This paper presents the analysis of 132 urban forms in London and Paris, two cities at similar geographical latitude, but of different urban geometry, focusing on the relationship between urban geometry and insolation of open spaces at neighbourhood scale. The method consists of three stages: (1) the geometric analysis of the urban forms, (2) their solar access analysis and (3) the statistical exploration of the results. Special emphasis is on the sky view factor (SVF), which is employed as an integrated geometry variable and environmental performance indicator. The comparative analysis of the two cities underlines the significance of urban layout for modifying the outdoor radiant environment, and reveals temporal characteristics of the relation between urban geometry and insolation of urban forms, induced by the varying solar geometry. Indicatively, the average mean ground SVF (mSVF) was found to be primarily affected by the quantitative characteristics of the open space, and able to predict average daytime insolation on March 21 and June 21 (R2?>?0.8), in both cities

Density and coverage values as indicators of thermal diversity in open spaces: Comparative analysis of London and Paris based on sun and wind shadow maps

Thermal diversity in open spaces is deemed highly desirable as it can enhance humans’ thermal experience and thus, the use of the urban space. This study explores the occurrence of spatial thermal diversity in open spaces in London and Paris, focusing on two parameters affecting the thermal environment. The method employed is based on the mapping of combined availability of sun and wind using DEMs and image processing techniques. The aim is to contribute to establishing a methodology for the assessment of thermal diversity, and to examine the relationship between this and the urban density and coverage variables. A mathematical formula for quantifying thermal diversity is proposed, and used for computing average and instantaneous values for 132 urban forms. The relationship of thermal diversity with the two variables is found to be statistically significant (R2>0.5), and best fit is achieved by polynomial curves. Solving the equations, the density and coverage values that maximize thermal diversity are identified for the two cities. To interpret the findings, the effect of built obstruction on the occurrence of the four microclimatic combinations considered (i.e. sunny-windy, sunny-lee, shaded-lee, shaded-windy) is examined. Lastly, examples of urban forms are discussed in relation to their geometry and performance