Now that the diffusers have become so much more important, the whole floor of the car has a much increased importance towards the efficiency of the whole car. Renault haven't missed out on that aspect and have added a double floor to its R30.
The team introduced a huge aerodynamic step at Sepang, including new sidepod panels, barge boards, a modified diffuser and a double splitter. Apart from its normal function of splitting air from in between the front wheels to the left and right sidepod, the new device also marks the beginning of a double floor. Right above the reference plane is now an open area of about 3cm high. Looking closely at the image you can also see that this floor space is extending under the side impact crash structures and under the whole width of the sidepod. While it is not perfectly clear yet how this air channel is used, the diffuser update that came with it suggests that this is used to feed on of the upper channels of the rear diffuser.
Just as with the underbody airflow, the stream in this channel will be accelerated due to the expansion that happens in the diffuser. As such, air is sucked from the front of the channel, reducing drag at the front while increasing downforce at the rear end of the car.