De-Light: a software tool for the evaluation of direct daylighting illuminances both indoors and outdoors - comparison with Superlite 2.0 and Lumen Micro 7.1.

Regarding techniques used to evaluate daylighting illuminances, recent year s have seen a steady increase in the use of computer programs, owing to inc reased computer speed and memory capacity. Despite a rise in the amount of available daylighting data, even the latest programs on the market only use standard CIE and IES sky models; besides, input climatic data and calculat ion procedures used by these programs do not always lend themselves to easy comparison: consequently, in the presence of different results from the pr ograms, it is not always clear which parameters are responsible for these d ifferences. From what has been said above and in order to examine closely various dayli ghting problems, we can better understand the need to develop a software to ol to analyse the influence exerted by the choice of different parameters a nd calculation models on final results. As regards the various daylighting components (direct-from-sky, direct-from-sun, internally-reflected and exte rnally-reflected), this paper is concerned with the direct-from-sky compone nt, since it is essential for the internally-reflected component calculatio n. In particular, the procedure which has been developed calculates the dir ect-from-sky illuminance component on the work plane and on the other inter ior surfaces that make up the room. Exterior illuminances on unobstructed h orizontal and vertical surfaces are also calculated, because they are neces sary for the calculation of the externally-reflected component and useful f or the reliability evaluation of simplified methods for the calculation of interior illuminances (daylight factor method and lumen input method). The computer program, named De-Light, has been developed in Visual Basic, a n object-oriented program language, in order to obtain the greatest flexibi lity in input and output procedures. In this paper, following a description of the program, we compare the resul ts obtained by De-Light with those obtained by two of the most common and r eliable daylighting computer programs, Superlite 2.0 and Lumen Micro 7.1. ( C) 2000 Elsevier Science Ltd. All rights reserved.