extractor fan

We bought our van for moving about the mutts as they don't fit in the VW caddy we have due to dog number 3 We like to have a fan to keep the dogs cool and to remove "emissions" The roof of the caddy is a wee bit crinkly which makes fitting a fan awkward So i have come up with a solution...

I tend to use my van for 2-3 days at a time each week, 365 days a year and this time of year condensation is a real issue, especially when cooking on propane which releases moisture as well as any steam from cooking. So I've been looking into active ventilation and was inspired by @TrevorK 's...