**5. Conclusions**

In this work the authors show the results of an intense analysis carried out on some innovative devices for daylight transport and natural ventilation in underground areas of buildings or rooms without any direct connection with outside. Starting from the knowhow, achieved in many years of numerical and experimental activity regarding the traditional light pipes, they propose two innovative devices: the Double Light Pipe (DLP) and the Ventilated Double Light Pipe (VDLP). By the DLP the problem of the encumbrance of a traditional light pipe installed in the centre of a two - level underground building is resolved because it illuminates both the passage and the final room, while the VDLP, in addition, is able to effect the necessary air exchange in the passage room.

The DLP was studied through a numerical and experimental analysis and its lighting performances are shown, while the VDLP was analysed by numerical methods by which its capacity to distribute fresh air in the passage room is investigated. Four VDLPs are composed in a basic modular form. The daylighting analysis allows the optimization of the centre distance between two adjacent devices to be set at 7 m. The successive numerical analysis regarding the thermo-hygrometric comfort indexes confirm that the square shape of a module, although perfectible, at this moment, is preferable to more complex geometric shapes because it offers the advantage of adapting to various possible compositions of modules.

In particular, the data of the numerical thermo-hygrometric and fluid-dynamics analysis enable us to conclude that the VDLP is an efficient tool for natural ventilation both in summer and winter conditions. Besides, in summer, it assures a certain degree of thermal comfort with regards to the spatial temperature in the environment as confirmed by data from PMV and PPD indexes. However it cannot effect the dehumidification action necessary to ensure complete thermo-hygrometric comfort conditions in summer. In winter, it cannot guarantee thermal comfort for the occupants of the passage room, but it can be considered an efficient tool for natural ventilation.
