Same issues at my athletic club....the yoga/spin teacher closes all the windows and fans--g-d forbid those of us at a "certain age" have a hot flash! But the road biker/spin teacher insists on the windows/fans on. She says that if it's too warm our bodies are working hard to keep cool and that's not helping in getting the benefits of the class. I usually plunk myself down on a bike near a window and open it....and if you don't like it then don't spin next to me! I do know that I can put more into the class when I'm cooler.
~~AG~~