A Ventilated roof component was built and tested in the outdoor testing facilities (Test Cells) of CRES, Greece. A conventional Greek roof structure of the same area was also installed in the roof of the Test Cell allowing simultaneous measurements in order to perform a comparative study of the performance of the two parts. Different configurations in the Ventilated roof were investigated, like ventilation air gap height and application of a radiant barrier. The tests carried out under summer weather conditions will be discussed in this paper. The experimental results showed a better performance of the Ventilated roof compared to a conventional roof construction under summer climatic conditions.