I asked my Physics teacher a question, and she wasn't quite sure. Maybe somebody here has an answer. Let's say I comfortably sleep at 70F. My bag is rated for 30F. Is it safe to assume that the sleeping bag is giving me a 40F boost? Would that mean that if the nighttime temps swings forty degrees below the late afternoon temps I should still be warm enough? For instance, if I'm wearing shorts and a shirt in the evening and still warm enough, the bag should hold up. And if it's a colder season and I'm wearing a down jacket and pants in the evening, I should still be warm enough in the same bag as long as I wear my warm clothes and the overnight temps don't drop more than 40F from the evening? According to my line of thinking, this bag will always make me 40 degrees warmer than the outside air.
If this is the case, then a 40F summer quilt (30 degree boost) over a sleeping bag rated to 30F (40 degree boost) should add up to a 70 degree boost. Does this make sense?
