Those are pretty dangerous ambient temps. You're going to have to do something major about your set up. I just barely manage in my basement which is 68-70 degrees.
Cardboard is better than nothing but I doubt that is going to fix your problem with a room at 60 degrees. Even with belly heat at 92 degrees you risk an RI with those ambient temps.
I wish I could offer more help but what you really need is a space heater.
