Let's stay on topic! He doesn't wan't to use it as a "blanket", he wants to stick two together at the edges to make a sleeping bag. I have heard of articles on these, but you would have a major problem with sweating.
when you sweat, your body is saying it's too hot so it tries to cool down. But trapped inside a thermal blanket sleeping bag, instead of evaporating,like normal, it would make your clothes damp and would make you cold, and, quite possibly, make you very uncomfortable when you wake up in the morning.
If you poked a couple holes at the bottom of the bag, it might help with ventilation. I hope this helped. <img src="/forums/images/graemlins/laugh.gif" alt="" />