Air circulation is key to avoid a rather unpleasant situation where you loose your whole crop. A cross breeze could do this, even a little battery operated fan. I'd suggest a close initial trim to avoid fan leaves creating a moist stagnant area on your bud.
In times of trouble look to nature.. Reverse engineering nature is a beautiful thing. Gofers use thermodynamics and bernoulli's principle to force air to circulate through their tunnels. By creating a mound on one whole opening they literally pull air from the other hole. Open the top vent and a lower window.. Shit hook a car battery up and put it in the shower with the fan on.
You need air circulation especially in an old I'm assuming musty possibly moldy motor home. Best of luck