There are plenty of opening windows in the trailer. Just using the ones on the four side corners provides plenty of ventilation. In fact, I don't think I have even had them all open at once, usually just two, and a bit of fan added in.
Non-operating windows seal better too, which for me is quite important. One of the issues with sliding windows is that they are the most prone to air leakage, especially in wind condition. Picture being the best, followed by awning and casement.
2017 Escape 5.0 TA
2015 Ford F150 Lariat 3.5L EcoBoost
2009 Escape 19 (previous)
“Most folks are about as happy as they make up their minds to be.” — Abraham Lincoln