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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.

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.

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.

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.

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.