I read many posts where folks discuss air conditioning a small camper. Great if it's an electric site. I built my camper as a comfortable step up from a tent and the majority of sites have been non electric. I've not had problems sleeping in my tiny camper but it has got me thinking.
I've mentioned before about sewing tubes onto a sheet and water slowly running through by thermosphion to an open tub of water on the roof. Kind of experimental.
I moved into an old farm house with friends when I was young. It was summer in Virginia and hot. There was an unused waterbed in my room. I was delighted. It was so cool that first hot night I fell asleep. Only to wake up hours later shivering with hypothermia. Yes, a water bed will pull all the heat from a humans body even when it is 90° outside. So with this in mind, I suggest sleeping on a thermorest pad filled with water instead of air. It's not as much water as a water bed so hopefully nobody freezes in their sleep. I actually might try this.
I have also noticed campers with no or one tiny window. No wonder it's hot in there! Put big windows on both sides and extra vents in the roof to get some air flow without fans. I found a super trick on this site. I used a screen door hook to prop my doors open about 3". This is very nice air right where we need it.
And a stupid idea if you are desperate. Put ice in a bag and throw that in the vent with the cooler thrown over the vent. The ice cools the air which drops down on the sleepers. I said it's stupid. :-)
Tt