DIURNAL-VARIATION OF SOLAR-RADIATION ON DIFFERENTLY ORIENTATED SURFACES OF MONUMENTS

In the Northern Hemisphere and, in particular, at 6 different latitude s (38-degrees, 42-degrees, 45-degrees, 48-degrees, 50-degrees, 56-degr ees) the flux of solar radiation which hits the vertical surfaces orie ntated in the eight main directions (North, North-East, East, South-Ea st, South, South-West, West, North-West) has been computed and compare d with the horizontal plane, at the time of the summer and winter sols tices and equinoxes. This study has been carried out with the aim of f urnishing a useful basis to calculate the quantity of energy which hit s a surface, as an integral to find out when the maximum energy hits i t, and to determine the time interval, during the day, during which a work of art is directly exposed to solar radiation. All this informati on is useful, in that solar radiation is an important forcing agent, a nd necessary in the biological and physico-chemical processes which le ad to the degradation of a work of art. Furthermore, it is also useful for the management of the rooms or the environment around the monumen t, to know whether it is situated inside or outside. Therefore, the am ount of energy reaching the various vertical surfaces has been compare d to the amount of the energy received by the horizontal planes and wh ich are normally acquired at the various monitoring stations. Moreover , the efficiency of the model depends on the correct choice of the atm ospheric transmission coefficient alpha. Finally, some examples of the partial results obtained when such a model was applied to the Scroveg ni Chapel, the Sistine Chapel, the Cathedral at Orvieto, the Horses of St. Mark in Venice and the Trajan Column, will be given.