A Survey of Solar Envelope Properties Using Solid Modelling

Abstract

Solar envelope is a concept for regulating solar access in urban planning. It is a roof-like imaginary surface over a given piece of land that controls the maximum allowed building height in order to avoid casting shadows on the neighbours during a specific period. The volume of solar envelopes regulates building density, depending on geometric attributes and time (plot size and proportions, orientation, ground slope, latitude, duration of insolation). This work compares the effect of such factors on the size of solar envelopes on a variety of land parcels, individually or in groups. Repeated applications of solid modelling are used to calculate in each case the values of 'Solar Volume Coefficient', i.e. the volume of a solar envelope per unit of its base as a measure for comparisons. Results show the influence of the various factors affecting the geometry of solar envelopes. Among other findings, it is also shown that solar envelopes generate urban densities lower than conventional urban regulations. The total volume of solar envelopes over an area ('Solar Building Potential') can be increased by raising the reference level of solar envelopes ('shadow fence' or 'solar fence'). Lower urban densities are compensated by facilitating solar applications, as well as by enhancing daylight, ventilation, and vistas in the urban context, thus creating new 'solar cityscapes' exemplified here on existing street patterns.