You may be looking for:
- Roof vents - (almost) a requirement in all vehicles used for camping or nomadic living. Often have powered fans.
- Mushroom vents - a mushroom-shaped vent that can be used on a roof or exterior wall.
- Gutter guard window vents - an inexpensive way to add temporary vents to your vehicle.
- Slam vents - hidden vents in nearly all vehicles that help release air from the vehicle when slamming doors shut.
All of these provide ventilation for your vehicle, which is an all-but-required feature when living in a vehicle. They can help with keeping cool and reducing condensation.