Ventilation is a big issue, I figure, in particular when you're sleeping in your van.
Many options crossed my mind, most of which would deprive the van of its stealthiness. Finally, I decided to go for so called "draft deflectors". Personally, I never liked those devices, since I think they look like a heavy smoker sits in the respective vehicle.
Anyway, those devices not only deflect draft when driving, they also keep out rain when a window is slightly opened. The draft deflectors look unsuspicious too.
So, I decided to buy a pair of draft deflectors. My garage gave me the advice that it would be best to spent 10 more bucks and get the manufacturer's real deal. Trusting my garage, that was exactly what I did.
€70 later, I got a set of draft deflectors. The installation instructions where not all that good and left a lot of guess-work open. Finally, I was able to install the devices.
Reading the instructions already made me fear the worst about closing the windows after installation of the the draft deflectors. The manual advices to "slowly close" the windows. With electric windows, slowly is what the motors figure to be slow... and up 'n down those windows went.
Finally, I decided to rub down the mating parts with petroleum jelly. Several attempts could finally close the windows... I figure that was "slow".