I’m so accustomed to the lack of rain here in California that I didn’t bother to check the forecast earlier in the week before taking the van to work. I had only half-completed the roof vent install, leaving the final waterproofing. One torrential downpour later I discovered that the waterproofing was needed!
Cutting a 14” square hole in your new van to install a vent and fan has been covered extensively on various forums, Antoine and Isabelle’s FarOutRide Transit blog, and elsewhere, but I’ll write up my version anyway.