Years ago I had a camper van that also contained a lot of the heat from traveling and we didn't want to run the generator to power the ac. So, we went the cheap route and bought a couple of approximately 12" square window fans from Kmart for about $12-$15 each and powered these 110v units with the onboard inverter. These fans were placed in front of the windows and were really effective and quiet. Today, we have a van camper with a roof mounted Fantastic fan that works really well but cost a lot more than those cheapo fans from Kmart.