One of the only times I have ever watched the show "Dual Survival" was when Cody Lundin made a shelter similar to a tube tent, but without a floor. The "front" wall was a plastic sheet, like a polycro but probably thicker. The "rear" wall was a space blanket, probably a thicker survival blanket-type rather than a thin mylar sheet like you'd get after a race. He then built a fire about 5+ feet away from the front wall. The plastic allowed radiant heat from the fire to enter and the space blanket reflected the heat downwards. I guess you wouldn't want the plastic up with a roaring fire but once it died down a little, it could be ok if you watched for embers. The floor was probably gathered leaves, duff, etc. According to the show (for what's it's worth), it was around 70* F inside, but maybe in the 20s or 30s outside. Think a low small portable greenhouse.
It isn't that often that one of those shows has something that seems to relevant to actual hikers in non-extreme situations, but I thought that was a clever idea. You'd still need insulation clothing, however.