Tips on insulating my leopard gecko's cage+question?

Yesterday, I moved into my college dorm with my leopard gecko and am having an issue with keeping the cool side of his cage at 75-77. I go to school in Illinois, and it gets very cold here (winter last year was awful, in the negative teens at some times).
Now, since I am in a dorm, I have no way to control the heat in my building (no one does), and while it is warm enough for people, whoever sets the heat is keeping it in the low 70's - which is too cold for a little gecko. I have moved his cage under my bed (it's lofted), far from the window in my room and have various clothes hanging on a rack that helps to block any cold air that might emanate from the window, (I have a digital temp reader, and it does read that it's colder in the room the closer you are to the window.) But still, even after moving his cage, I use my digital thermometer and it reads that the cool side is 72-74, which is not good.
I have a good thermostat (Herpstat1) that keeps the hot side of his tank at 90-91 degrees and the surrounding area in the 80's/upper 70's, so there's no problem there... but what can I do to insulate his cage better, to keep his cool side just a bit warmer?
I should mention that I do have an extra emergency heat pad and an extra thermostat that I brought with me just in case something like this happened... but I wanted to know if anyone (who lives in colder areas, especially) had any cage insulation tips before I install these.
I did try putting a dry towel over the top of the cool half of his cage, but that didn't appear to bring the temps up... but I thought stuff like that is supposed to help with that?

Please help!

Update: sorry for double posting. I put a jacket over a different part of his screen top cage and the temps on his cool side have been brought up to 75.5-76 when I checked them this morning. Still, for future reference, if anyone has any tips and tricks on other methods they use for insulating their cages, I would love to hear about them!

I wouldn't be too concerned as long as you're providing a temperature gradient. Your gecko will find the temp where he/she is comfortable and spend most of their time there. I just checked the temps this week in Islamabad, Pakistan. The lows range from 64-70 degrees with highs in the mid 90's.
If you find that insulating your cage is necessary you could always try foam panels from Home Depot on the sides and back.
http://www.homedepot.com/p/Project-P...0?N=5yc1vZbaxx
You could also place a sheet of plexi glass over half of the screen top (the warm side) to prevent vertical heat loss.