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.
This study focuses on the widely accepted principle that the equatorial sides of a building offer the optimum solar potential for solar space heating. A comparison between the solar irradiation on the south walls and horizontal roofs of buildings in London and Athens highlights the energy benefits of facing the sky rather than the equator. Four building examples exemplify practical ways to utilize the rather neglected potential of roofs as solar collectors for space heating.
Purpose The objective is to provide a quantitative insight on the dynamic nature of insolation on the building perimeter according to location, season and orientation. Such understanding is necessary for deciding on solar control strategies in diverse climatic environments, from low to high availability of insolation. Design/methodology/approach This study explores the seasonal changes of solar irradiation on building façades of various orientations at five locations with diverse climates (Reykjavík, London, Athens, Riyadh, Lagos). Solar data collected from the European PVGIS database is used to study the monthly distribution of global solar radiation incident on building façades at cardinal and ordinal orientations, as well as the proportions of its components. Findings The results illuminate the effects of the various factors on insolation. Among others: In all locations, horizontal surfaces receive more annual irradiation than any façade. In summer, east/west facades receive more radiation than south, hence solar protection on those directions is more important than on south. The beam fraction varies seasonally on south and north facades, but not so on east/west. Local atmospheric conditions can offset the importance of latitude on insolation levels and composition. Originality/value The paper utilises commonly available data to correlate insolation values and types under different factors across the globe, offering a better understanding on insolation for the design of greener buildings.
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