In this work tubular light pipes performances are studied by means of a compared numerical and experimental method. The numerical analysis is effected by ECOTECT, RADIANCE (Adeline 3.0) and ENERGY-PLUS soft-wares and the obtained results are compared with experimental data got by a reduced scale analysis carried out into the artificial sky in CERSIL, Polytechnic University of Torino. An intense previous real scale experimental analysis on a two light pipes apparatus installed into the Technical Physics laboratory in Architecture Faculty of Pescara showed that the possibility to characterize light pipes performances is limited by accidental factors, such as transitory external climatic phenomena. On the contrary, both numerical and reduced scale experimental analysis present the advantage to furnish results in repetitive conditions, so both these methods are able to do general evaluations about light pipes performances and the influence of some environmental parameters on internal distribution of light. In this work a comparison between data obtained by the above mentioned soft-wares and by experimental analysis is effected with the aim to evaluate the influence of boundary walls reflections on inside light distribution. Besides, the availability of experimental data allowed to determine the sensibility of simulation programs to this environmental parameter.