**1. Introduction**

290 Solar Radiation

Chella, F.; Gentile, E. & Zazzini, P. (2007). Natural light in new underground areas of a

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Jenkins, D., Zhang X. & Muneer, T. (2004). Formulation of semi-empirical models for

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Zazzini, P. ; Chella, F.; Scarduzio, A. & (2006). Numerical and experimental analysis of light

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solution, *Building and Environment*, Vol. 38 pp. 965-972.

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01, 2006

77-86.

pp. 2288-2300.

September 6-8 2006

historical building: an example of application of double light pipes in preservation of the architectonic heritage, 6th International Conference on Sustainable Energy Technologies SET 2007, pp. 232-237, Santiago de Chile, Chile, September 5-7 2007 Chella, F.; Zazzini, P. & Carta, G. (2006). *Compared numerical and reduced scale experimental* 

*analysis on light pipes performances,* 5th International Conference on Sustainable Energy Technologies SET 2006, pp. 263-268, Vicenza, Italy, August 30-September

predicting the illuminance of light pipes, *Energy Conversion & Management*, Vol. 46,

pipes' performances: comparison of the obtained results, 23th Conference on Passive and Low Energy Architecture, Vol. 2, pp. 219-224, Geneva, Switzerland, Solar radiation is the only renewable energy source readily available at every building in the world. Whilst urban regulations and meteorological or geographical factors often impede proper ventilation, to design a building without at least a view of the surroundings is tantamount to making plans for a prison or a tomb, and no culture would accept that as a permanent residence. Thus, the necessary connections with the environment are provided by apertures through which radiation is admitted.

Since antiquity, a multitude of researchers and scientists have striven to find the magnitude of solar radiation incident on a horizontal surface at the earth's crust. A few of them have found adroit correlations between horizontal and vertical irradiation. These seem acceptable for the analysis of building facades since direct measurements are in many cases not feasible due to obstructions, interferences with ground reflection or simply because of economic constraints.

However, it is still surprising how few scholars are familiar with the distribution of such radiation inside the chambers, precisely where it should be used. To be sure, if one wants to transfer a certain amount of energy to human beings, the task needs to be accomplished piecemeal, or the consequences could be devastating as, unfortunately, everybody knows.

In the ensuing chapter, the author intends to explain the fundamentals of radiative energy transfer, a discontinued branch of geometric optics that colligates time, space and architecture in a single operation. The author would also try to ensure that every person is able to reproduce his experiments at home by virtue of computer simulation and analysis.
