In the past few days I was working on an extra fan component for the E2. The main reason I created this thing is that I when I wanted to stick the tube out of the window, it became rather vertical, so there was a need of enhancing the ventilation.
The module can be threaded onto the end of the ventilation tube. It contains a small, 40mm diameter fan inside (SEPA LF40B12), and as currently I do not have a soldering iron at home, I used a low-voltage connector with screws (TRU Components DC 12-F). The module is operating from 12V DC. The housing was designed with openSCAD and printed with a 3d printer.
The efficiency of the module is still under investigation, but if anyone is interested, I would be happy to share more details as well as the 3d model.