Having the ability to circulate air through your van may be the single most important part of your build. I really can't overstate this enough. With a well functioning air circulation system, you'll be able to keep it to a bearable temperature even on very hot and sunny days. Without it, your van will be miserable in warm weather - and this is coming from someone who's spent way too many nights sweating in a van without proper ventilation.
Beyond just comfort, good airflow solves several critical problems:
Temperature management - On a sunny day, your van is basically a greenhouse. Even with good insulation, without airflow, temperatures can climb 20-30°F above outside temp very quickly. A good fan pulling air through can keep your interior within a few degrees of outside temperature.
Condensation control - When you're sleeping, you're breathing out moisture. Cooking adds more moisture. Without ventilation, all that moisture condenses on your windows and walls, leading to mold and rust. A fan running on low overnight makes a huge difference.
Cooking smells and fumes - Cooking bacon or fish inside a closed van? Those smells will linger for days without proper ventilation. With a fan running, they're gone in an hour.
Air quality - Just having fresh air circulating makes the van feel more livable. Stale air in a small space gets uncomfortable fast.
Almost all van builds incorporate a roof mounted fan for this reason - there are a few brands, but the Maxxfans are the most popular choice for most people. While we generally advise for saving money on off-brand choices for all sorts of components, I think the higher end Maxxfans are one place where spending the money is worth it.
There are cheaper roof fans (Fantastic Fan being the most common alternative at about $100-150 vs $300-500 for Maxxfan). Here's why I think Maxxfan is worth it:
There are several options in the Maxxfan Deluxe range. Here's what you need to know:
This is the minimum I'd recommend
This is what most people should get
This is the "fully loaded" option
I think that at the very least, being able to leave the fan open and running and not worry about a surprise rain storm drenching your interior is well worth it. So, bare minimum: get a Maxxfan Deluxe (not a cheaper brand).
From there, I think the inflow option isn't critical for most people - most of the time, you'll likely operate it in exhaust mode. However, typically you'll have the fan mounted above your bed, and having the option to pull air in for a fresh breeze directly on you if it's hot and you're trying to sleep can be pretty nice. On really hot nights, I sometimes run it in intake mode on high to blast cool night air down on me - it's genuinely helpful.
As far as the remote goes, again, it's not critical, but especially if the fan is mounted back over your bed, not having to crawl up to adjust it is quite nice. Being able to turn it on or adjust the speed from bed is a quality-of-life thing that I didn't think I'd care about, but actually use all the time.
My recommendation:
Get the Maxxfan Deluxe Plus (reversible, no remote) for most builds. It's about $380-420 and hits the sweet spot of features vs. cost. If budget is really tight, the base Deluxe works fine. If you want maximum convenience, splurge for the remote.
This is one area where I'd deviate from my usual advice to go with a budget brand. The Maxxfan's ability to stay open and running in the rain without relying on sensors is genuinely worth the premium - you just don't have to think about it.
That said, you don't have to pay full retail. I've bought brand new, unopened Maxxfans on Facebook Marketplace for both of my builds at around $200-250 (vs $380-400 retail). People buy them for builds they never finish, or buy the wrong model. It's worth checking Marketplace and Craigslist before paying full price.
If the Maxxfan is out of your budget even used, Vevor makes an RV-style roof vent fan that's significantly cheaper. It's reversible and comes with a rain cover lid. However, it doesn't have the Maxxfan's integrated rain shield that lets you run the fan while it's raining - you'd need to close it in a downpour or rely on a basic rain sensor. For fair-weather builds or very tight budgets, it's a reasonable option - but if you can swing it, I'd go Maxxfan.
This is worth addressing because some people worry about this:
Running on low overnight (8 hours) uses only 40-80 Wh. That's nothing compared to your fridge or other devices. Don't hesitate to run your fan - it's one of the most important power draws you have.
One overlooked thing to consider is where you want the air that the fan draws to come from. If your fan is running in exhaust mode, but you don't have any ventilation for it to draw air, it won't be very effective. The fan needs intake air from somewhere to create flow.
I personally like the approach where you have the roof fan mounted in the rear and crack your front windows to allow air flow through. This way you can get a nice breeze from the window if you're sitting in a front swivel seat, and you can easily roll the windows up or down for more or less venting.
You can also cheaply and easily install window visors (also called rain guards or smoke guards - brands like WeatherTech, AVS, or cheap ones on Amazon for $30-50) that keep the rain out with the windows cracked, and that make it less obvious that your windows are cracked. With window visors, you can leave your windows down 1-2 inches in the rain without water coming in, and from a distance it's not obvious your windows are open at all.
Some people install a second passive vent (like a mushroom vent or low-profile vent) near the front of the van. These don't have fans, just allow air to enter passively.
Personally, I don't see much reason to bother installing a supplemental vent if you can just crack the windows. The windows give you more control and don't require cutting your roof again.
If your van has windows on the doors, these can work as intake points too. Same concept as the front windows.
The key to good airflow is creating a path for air to travel through your van:
Finally, some people choose to install two roof fans, and have one draw air in from one end of the van, and the other exhaust air from the other end. I think this would help create even more airflow, but I don't think it's a necessity - probably more of a nice to have for higher-end, no expenses spared builds.
Don't forget about bugs! Your Maxxfan comes with a built-in screen, but if you're leaving windows cracked, you'll want protection there too:
If you're camping in buggy areas, having screens on your windows makes a huge difference in livability.
If you're trying to be stealthy (camping in parking lots, etc.):
If I could only have one thing in my van build, it might honestly be the roof fan. It's that important. Good insulation is nice, but without airflow, your van is still going to be miserable in warm weather. A heater is nice, but you can use a sleeping bag. A fridge is great, but you can use a cooler.
But a good ventilation system? There's no real substitute. It makes your van comfortable, controls condensation, keeps air fresh, and just makes the whole space more livable.
Don't cheap out here. Get a good Maxxfan, install it properly, and use it liberally. Your future self will thank you on every hot day, every time it rains while you're cooking, and every morning when you wake up without condensation all over your windows.