The sun and architecture

In the sun/architecture relationship, architectural form plays a key role, not only in ensuring the transmission/occultation of the sun's energy resources to an extent yet to be quantified, but also in making the exterior appearance of a building more legible through the interplay of cast shadows. For a long time, the diurnal evolution of cast shadows was a difficult thing to represent, which justified the famous "45/45 shadow" convention, but computer tools now make this very accessible.

Then there's the question of solar protection and its inverse, solar capture, by means of openings and facade walls or "5th facade". Here again, computer-aided design has a definite advantage, especially when it comes to answering the question: "What are the sunlit and shaded zones, at a given moment, under the effects of an architectural mask? The answer is automatic, but on a drawing board, the expression of this answer requires the layout of numerous images that don't give global information on the "performance" of the architectural form in question.

This is why we prefer to focus on the question: "At what times of the year is an elementary building surface totally, partially or not at all shaded by an architectural mask? The answer then takes the form of solar iso-transmission curves plotted on a "solar diagram". The computer can be used for this, but it's also possible to use the "solar diagram" tool by hand, generally confined to representing the sun's apparent path against masks in the distant environment.

The aim of this article is to show all the possibilities offered by the solar diagram when the challenge is to diagnose the "protection/transmission" performance of an architectural form.