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How can I regulate my temperature in a -15°C down sleeping bag when it is cold but not quite -15°C?

I have a down sleeping bag rated at -15°C. Used it at a previous hike where the temperature went down to -5°C. I was uncomfortably hot, and as a result didn't sleep well.

It is a mummy shaped bag, so the zipper only goes down halfway.

Tried putting my arms out of the bag, but my arms gets too cold.

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up vote 6 down vote accepted

Buy an Overbag.

  1. Use the Overbag when it's too warm for your down bag
  2. Use the down bag at and around -15C
  3. Use the Overbag and Down Bag together when it's colder than -15C

AND if you want to get real fancy get a Vapour Barrier Liner and use all three together for expeditions and temps below -30C. You now have all your bases covered!

This is much more cost effective than to buy a summer bag, your -15 bag, and an expedition bag...

If you're too cold in the overbag but too hot in the -15C mummy bag, try playing with your layers, add a base layer top and bottom while in the overbag, or even throw on a nano puff or fleece top...there are many ways to regulate your body temp. Vests are a great way to keep your core warm but your arms still feel nice and cool.

I hope this helps!

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When its like -10C or -5C and both too cold for just the liner but too warm for the whole bag, you could use the liner with the bag as a sort of blanket over you. – User1996 Jul 18 '14 at 0:49

Unfortunately you are limited in your options:

  • use a mat under you and the sleeping bag as a blanket. This will be a lot colder, though
  • buy another bag, perhaps rated to -5 as an alternative. If you have the carrying capacity, it can be simpler to have a lighter sleeping bag plus blankets, so you can adjust the temperature to suit. Or you could go for a sleeping bag with a full length zip.

The second option would be my preferred one - I have a range of sleeping bags based on expected conditions, and any of them (except for the coldest rated) will work over a reasonably wide range.

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Some sleeping bags are designed so you can shift the down to the side in order to help with thermo-regulation. – ppl Jul 16 '14 at 18:41

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