SOMBRERO: shadow calculations on arbitrarily oriented surfaces as a preprocessor for simulation programs

SOMBRERO, a PC-program running under the operating system WindowsTM, calculates the proportion of shaded area of an arbitrarily oriented surface surrounded by shading elements as a function of time and location. The reduction of (isotropic) diffuse radiation due to different kinds of obstacles is calculated by means of view-factors, too. Calculation results are displayed online, and ASCII output files are produced that can be read into dynamic thermal building simulation systems or spreadsheet programs. Three examples for the practical use of SOMBRERO are presented:

1. The windows of an office are shaded by some surrounding buildings. With SOMBRERO, the influence of shading by these buildings on overheating in summer was investigated.
2. The optimum position of a solar collector on the roof of a one-family house was determined. 
3. The effects of a number of deciduous trees that were to be planted in front of a two-story building on the heating energy demand,