Originally Posted by
Raphtheone
I'd suggest getting a small circular floor fan that you point upwards and place on the floor behind the computer (the size of a CD/DVD/Blueray disc would be ideal). You seem to have ample space beneath the computer to place it. It doesn't have to be something expensive, a (very) low-RPM fan would be enough to move the heat away so it won't congest behind the computer. With one of those, your current solution, and cramped space, would have a minor impact on heat dissipation at worst, assuming you don't have deep shelves right above or the ceiling at 1,4 meters, your pictures doesn't show!
Picture-googling "small floor fan" gave a lot of results.