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big_jud

By big_jud

05 December 2008 12:22

Does a sleeping bag inside another sleeping bag significantly boost the performance? Or, is it better to get one thick one? (Don't really want to do the second option as I would probably never use a 5 season sleeping bag again!)

Answer

GrahamThompson

By GrahamThompson

Sleeping bags keep you warm as they are able to trap small pockets of air. The more air trapped inside a sleeping bag, the more insulation it will provide and the warmer you will be. So in theory, yes, placing a sleeping bag inside a second sleeping bag should be warmer. The Ultralight range of sleeping bags by Khyam for example uses this principle to create a warmer bag.

However, for this to work the sleeping bags need to fit inside one another without squashing all the small air pockets - otherwise the benefit will be reduced. The perfect set-up is an inner bag which is a little smaller than the outer bag, so that it fits neatly inside to provide the maximum number of air pockets and therefore maximum insulation. For these two bags to fit inside one another perfectly, one would have to be tight when used on its own and the other would have to be baggy when used on its own. So they might work well together but no so well on their own?

As a general principle it may be better to have just one bag.  Two bags are only better in very specific conditions, such as trekking from low altitudes in hot countries to high altitudes - say Nepal. 

Finally, buying two bags will be more expensive and heavier and have a greater pack size. So the short answer is, I think it is better to have separate bags overall.

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Are two thin sleeping bags better than one thick one?

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sthomper

sthomper says

RE: Does a sleeping bag inside another sleeping bag significantly boost the performance? Or, is it better to get one thick one? (Don't really want to do the second option as I would probably never use a 5 season sleeping bag again!)

 can anyone speculate on how this http://www.lafumausa.com/catalog/t-30-to-50/431-x700-xl.html 

45 degree, 1lb 6 oz. rectangular bag would do over  this http://www.lafumausa.com/catalog/t-30-to-50/432-x600.html   45 degree mummy shaped, 1 lb 4 oz. bag???  

would the total weight be comparable to a 20 degree or below bag??

if so would this offer more flexibilty as a sleeping bag set up???  two bags at roughly the equivalent weight of a 20 degree bag when temp required it and while still having a lighter bag for warmer temps???

 

11 October 2010 04:05

ptc

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ptc says

Re: Are two thin sleeping bags better than one thick one?

I've used two sleeping bags all winter, a PHD Minim Ultra and Combi, and it's been brilliant. They're designed as a pair, so the sizing is right, there's no weight or bulk penalty over a standard winter bag. I've been sleeping in base layers instead of my usual extra layers I've never been so warm camping in winter.

It won't work with all bags as the sizing won't line up, but it's something worth exploring for sure.

04 March 2009 22:19

aultguish

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aultguish says

Re: Are two thin sleeping bags better than one thick one?

One problem with 2 sleeping bags..........doesn't leave you too much room in a normal weekend camping sack (45litre-ish) for anything else, especially if you are out there on your own with tent etc.

27 February 2009 12:28

jub2k

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jub2k says

Re: Are two thin sleeping bags better than one thick one?

I went camping in the peaks a couple of weeks ago, when the snow was plentiful, it was well into the minus temperatures overnight.

I used my normal bag inside a cheap one, both are synthetic, hot water bottle in the bottom, i was toasty warm all night, so cold in the morning the outer bag had frost on it, but i was still cosy and the hot water bottle was still warm to the touch too...

24 February 2009 12:36

GuyHurst

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GuyHurst says

Re: Are two thin sleeping bags better than one thick one?

Two sleeping bags can work well and give a lot of flexibility but, as Andy advises, make sure the outer one doesn't compress the filling of the inner bag. One way to avoid this is to use a close fitting lightweight down bag (PHD Minim, Marmot Helium, Alpkit Pipedream maybe) as the inner and a synthetic fill down bag as the outer. The synthetic bags tend to be looser cut so this lets the inner baf loft. Also, the outer bag, being synthetic, will be more resistant to moisture, in effect protecting the more vulnerable down inner.

Such a system will never give quite the warmth to weight ratio of a good four or five season bag, but it is a lot cheaper.

23 January 2009 18:23

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