A cool fresh night of sleep

Doctor: Have you taken my advice and slept with the window open?
Patient: Yes.
Doctor: So your asthma disappeared completely?
Patient: No, but my watch, TV, iPod, and laptop have.

"Ventilation"
If you can't open or crack your windows to get fresh air, keep a fan in your bedroom. Consider installing a quiet overhead fan.
Cross ventilation is the best way to create a healthy sleep environment. If you can, open windows (and doors, if possible) to provide fresh air. Research has proven it's conducive to good sleep to have some air movement in a person's bedroom; even if it's not fresh air.

"Bedroom Temperature"
The ideal Bedroom temperature is between 60 and 65 degrees Fahrenheit. For most people, 65 degrees Fahrenheit is more conducive to restful sleep, but if you must err, do so by sleeping in a cooler, rather than warmer, room