That kinda puts the lie to the common concept of 'warming up' the sleeping bag. In my experience, backpacking forums are replete with cautions that larger bags needlessly suck up body heat to warm the larger space...hence the popularity of mummy bags. I never gave much thought to that contention but it seemed logical. And I've slept in enough bags to know that, on a chilly night, it takes some time to rewarm a cooled-down bag.

If in fact the theory is true would it not apply to wearing warm clothing in lieu of using a bag? Wouldn't less body heat be spent warming up the surroundings and more be available to keep one's body warm? Indeed, properly fitted layered clothing may be warmer than a sleeping bag. And that's what this sleep system is, a fresh base layer covered with a layer of insulated clothing.

Perhaps the key phrase is, "as warm as...". If one is comfortable...if one is 'warm', one doesn't have to be 'warmer.' That's implicit in lightweight backpacking...don't over do it...don't carry more than you need...don't over engineer... The kind of sleep system proposed here and the one I use is has it's limits as do all systems. But the limit of my system is keyed to where and when I use it. I watch the weather before and during a trip, I know how long it will take to bail out, I carry enough to allow a 10° margin (10° colder than forecast). Except for the safety factor, I don't carry more than I need. And that applies to the sleep system, cooking fuel, food, extra clothing, etc. In fact and as I posted previously, I carry the cold weather clothing specifically for the safety factor and this system allows me to get some dual use (read, some use) out of those three pounds. Fifty degree swings during any one day are common in the arid mountain west...freezing temps occur in any month once you approach 6000' or so. I gotta carry the clothing 'just in case' but, May-Oct, the clothing has yet to be used when I'm hoofing down the trail. Still, in a hammock it provides comfortable sleep into the 20's, the pad being the limiting factor. On the ground, drop the range another ten degrees.

Bags can be efficient and comfortable. They can also be bulky and add pounds to a backpack. What they are not is essential. Bags were invented in the mid-1800s. In North America prior to that, Native Americans, explorers/mountain men, settlers and others didn't use 'em. And ya' know what? There were survivors.

It's all very individual and specific to who, what, where, when. It can save weight and I believe that's in the spirit of this forum,"The Lightweight Zone." If you're experienced and skillful enough, if you practice good judgement and safety, you can minimize pack weight. And that includes the sleep system depending on who you are where you are when.

FB