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.


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!

  • 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.

  • 1
    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

If you can, unzip your sleeping a little bit and stick your feet out. If your feet are cold than you body will be cold too. If your head or your hair is cold your body will be cold too. So if your hair/head or feet are cold your body will be cold too.

  • You don't even need to stick your feet out. Just unzipping the bag at the bottom oats enough air in to make a big difference. A thin liner helps even out the cold feet and warm torso (even my cotton liner for bunkhouses does that) – Chris H Jan 30 '18 at 7:47
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    How are you meant to stick your feet out when the zipper only goes down halfway? Also, "if your hair is cold, you body will be too" is untrue: hair's a good insulator with relatively low thermal mass. – Pont Jan 30 '18 at 10:56
  • @Pont the majority of decent sleeping bags can be unzipped from the bottom as well, for precisely this reason. – Chris H Jan 30 '18 at 12:59
  • @ChrisH per OP "It is a mummy shaped bag, so the zipper only goes down halfway" This is not an answer to the OP's Question. – James Jenkins Jan 30 '18 at 13:11
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    @ChrisH OP explicitly says "the zipper only goes down halfway"; they're not asking about the majority of decent sleeping bags, but about the one they've actually got. "Buy a new sleeping bag" might constitute a valid answer to the question, but "unzip your half-zip sleeping bag at the bottom" clearly doesn't. – Pont Jan 30 '18 at 13:28

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