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Using a liner as a stand-alone ‘sleeping bag’
Ask Baz

Using a liner as a stand-alone ‘sleeping bag’

We’re often asked if you can use a sleeping bag liner instead of a sleeping bag in warmer temperatures.

Broadly, the questions fall into two categories: those end-users who are intending to sleep outdoors, either in a tent/shelter or under the stars and those end-users who are intending to sleep in a hostel.

For ‘outdoors’ users, the liners which would come into question would be the Reactor, Reactor Compact Plus, Reactor Extreme, Reactor Fleece, and the Adaptor.

For hostel sleepers, the Silk, Silk-Cotton and Expander liners would be appropriate.

When sleeping outdoors, the main factor to be aware of is moving air. The Reactor and Adaptor liners are primarily designed for use inside a sleeping bag, so they allow enough air to pass through their fabric to guarantee a comfortable night’s sleep in that configuration. Breezes and drafts in an outdoor situation will also pass through the fabric and rob you of the warmth you have generated. If you are inside a tent or shelter, this is less of a factor, but ‘under the stars’ you may need something to act as a windproof barrier laid over the liner; for instance a poncho or an ultralight sleeping bag cover.

The hollow-core Thermolite fibers and three-dimensional knitted structure of the Reactor series are very effective at trapping warmth. Providing you are dressed in dry base layer garments, in still air, you can expect a Reactor to work as a ‘stand-alone’ sleeping bag down to air temperatures of around 55°F/13°C and a Reactor Extreme will be comfortable down to around 50°F/10°C. An Adaptor will be comfortable down to a couple of degrees warmer than a Reactor.

When sleeping in a hostel, moving air is likely to be much less of a factor. Essentially, the liner is primarily providing a comfortable sleeping environment (and, of course, providing a hygienic refuge from less-than-pristine sheets and possibly bed bugs – see the blog post ‘Which liner should I choose’). Many hostel/backpacker’s hotel users will be sleeping in tropical or sub-tropical locations where there is no concern about maintaining warmth; in those locations a Silk, Silk-Cotton or Adaptor Liner is a comfortable haven at night which is easy to wash and quick to dry.

If you are hiking on one of the classic pilgrim walks, such as the El Camino Santiago, you may encounter temperatures closer to those discussed for ‘outdoor’ users above, If this is the case, an Adaptor or a Reactor would be the liner of choice.

10 thoughts on “Using a liner as a stand-alone ‘sleeping bag’

  1. avatar Baz says:

    G’Day Andy – If you’re a relatively warm sleeper, and you have a set of medium-weight base layers (top and bottom), a Reactor Extreme will work as a ‘stand alone’ sleeping bag down to 15°C provide you are sheltered from the wind (as you would be inside your tent). If you would like a little extra warmth for a small increase in weight, the Reactor Fleece Liner is well worth considering. And if you would like more flexibility at an even lower weight, the Traveller Tr I sleeping bag is the ideal travel blanket / quilt / summer sleeping bag.

    We’d be happy to go into more details on any of the above – just email us at


    The Sea to Summit Team

  2. avatar Abdrea says:

    Hi. I’m planning a 7 days trek along the Via Francigena route in Tuscany/Italy this August. Avg MIN temperatures are 63 °F (17 °C) (with a slightly less avg MIN in the hills between Lucca and Siena). I intend to bring with me a tent (MSR Hubba Hubba 2NX) and a sleeping mat (Sea to Summit Ultralight Sleeping Mat) and I’m deciding wether using a sleeping bag or only a liner inside the tent at night. I read that camping with a tent and a liner (Reactor Extreme) could be perfect (and in warmer nights the combo StS Ultralight Mat and StS Reactor Extreme should suffice to enjoy a cozy sleep under the Tuscan sky. I’ll be glad to read your advice and thougths. Thanks. Andy (Bologna, Italy)

  3. avatar Baz says:

    G’Day Vi

    Thanks for your question. As the blog post says, moving air is the biggest factor in using a liner as a ‘stand-alone’ sleeping bag. The slightest breeze will take away much of the warmth from inside the liner.

    Providing you are dressed in dry base layer garments, in a tent, you can expect a Reactor Fleece Liner to still be comfortable down to temperatures a little under 50°F/10°C. If you are the kind of person who feels the cold easily, you might use 55°F / 13°C as a guide


    The Sea to Summit team

  4. avatar Vi says:

    Hi, I’m getting Reactor Fleece liner as a stand alone sleeping bag for summer. I wonder how low the temperature can i use with this bag given sleeping in a tent with inflatable sleeping pad r-value 4.5? Thank you very many :)


  5. avatar Baz says:

    G’Day Sarah – thanks for your question. 10°C air temperature (even in a bivy) is probably close to the lower end of what you would regard as comfortable sleeping in just a liner. At the other end of the scale, 20°C (especially if it is humid) could mean quite a lot of condensation inside the bivy.

    On balance, we’d probably recommend the Reactor liner – it will be (just) warm enough in the colder temperatures you mention, and will wick well enough to keep you comfortable (if it is kept away from fabric softeners during the wash cycle) in warmer temperatures.

    If you would like more details, email us at – please let us know which Gore-tex bivy you have, and where/what kind of conditions you would use the bivy/liner combo in.


    The Sea to Summit team


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