Post date: Apr 14, 2015 7:07:45 PM
We've heard this story for years, even from a salesperson at REI. Well, he wasn't talking to us, but to an attractive young lady, so he may have had other intentions. But the story he told was that you will sleep warmer in a down sleeping bag if you sleep nude.
Hogwash.
Keeping warm is all about insulation. The more insulation you have, the warmer you will be. (This was brought home to us as we tried to sleep warm on our most recent trip to Yosemite, with temps into the 20s. P was fine in his bag, M never really did get fully warm that night.)
So where did this silly myth come from? We think it started with a treatment for hypothermia. In that case, the victim is so cold that his body temperature can't warm up the bag....and hypothermia becomes a critical problem. In that scenario (and ONLY in that scenario) it makes sense to put the person into a sleeping bag nude---but you must also put ANOTHER person in the sleeping bag nude. That second person will provide the body heat to warm up both the bag and the victim. Without the warm body, the cold body will suffer even more.
There is also a rare situation where a sleeper will have so many clothes on that the down in his sleeping bag is so compressed that it won't fully reach its insulation properly. In that case, more isn't necessarily better.
But the laws of physics are pretty clear on this one: More insulation is better at keeping you warm than less insulation. And dressing in layers on a cold night will keep you warmer than sleeping nude in the same bag. No matter what that young chucklehead at REI tells you.
Before we could write this, we were sent a lovely article about other myths backpackers encounter. Here's a link to that story---which is a fun read. We particularly liked the line about the two man tent, since we prefer a three man tent for the two of us:
http://sectionhiker.com/10-backpacking-gear-myths/