It's hot where I live, and my running shoes stink; therefore I knew I wanted some good venting/air circulation. The van came with a ceiling vent, but I took it out and insalled the MaxxAir 4500. It wasn't cheap, but was worth it. It may be my favorite thing in the van.
Here is what you will need:
Remove Old Fan/Cut hole for Fan
I didn't like the placement of the fan the original owner had intalled (I put a skylight there), so I cut a new hole and moved it forward. Make a pattern the size of the fan out of cardboard (this eliminates the need to measure) and then trace the outline of the cut-out. Drill holes at the corners and complete the cut-out using the jigsaw.
butyl tape & insert Fan
Butyl tape can be found at most RV stores or online, it provides a great seal between the metal and the fan. Make sure there are no gaps, apply the tape right to the fan and then press onto the ceiling where desired. Finish by drilling screws into place. That's it, easy. Enjoy the breeze.