Hello,
Regarding back pain after sitting in front of the AC: Cold air can effect your muscle after prolonged exposure in any position. However sitting often places an uneven load on your back region if not properly supported and balanced. Therefore I would suggest seeking 1st a spinal check up with your local chiropractor to determine if you have any issues that can be treated and than limit your time sitting in front of your AC.
Respectfully,
Dr. T
Advanced Chiropractic Centers
Grass Valley CA 95945

Victoria M. Tutak