Sleeping Bag Liners: Cotton, Silk or Fleece? How to Choose

A sleeping bag liner can be both an alternative and a supplement to your sleeping bag. On a summer walk along the Camino Portugués I chose to bring only a liner, because carrying a full sleeping bag would have been far too warm. On top of that, I was delighted by how little a liner weighs and how little space it takes up in the backpack compared with a sleeping bag.

If you are wondering which liner to choose, or whether you should use one inside your sleeping bag at all, read this guide before you decide.

What is a sleeping bag liner?

Sleep and comfort are rarely top of mind when you plan your next adventure. You get recommended a mountain of exciting outdoor gear while preparing, and it can be hard to prioritise. Maybe you have heard of a sleeping bag liner without quite knowing what it is or what value it adds. Let me clear that up.

A liner is made as an inner layer for your sleeping bag, and the easiest comparison is the sheet on your bed at home. A liner makes your night’s sleep more comfortable, extends the life of your sleeping bag, keeps the bag clean, helps regulate warmth, and reduces the moisture and sweat that easily build up inside a sleeping bag.

That all sounds great, so why does not everyone always carry one? Simply because the need is not always big enough. On the Camino I have had nights in the albergues where a liner was a clear success in both cold and warm conditions, and other trips where it never left the pack. The material differences below will help you judge your own need.

Which liner should I choose? Consider this first

Broadly there are two types of liner. The best known is the kind you use inside your sleeping bag, cut in the same tapered shape, often called the mummy shape. The other type is rectangular, and it shines when you travel between many places where beds come with duvets or blankets and you would rather not sleep directly on the bedding. The rectangular cut is simply a more relaxed shape to lie in.

Before choosing, consider these three things:

1. Shape: mummy to pair with a sleeping bag, rectangular for beds and warm nights
2. Price: how much use will it get, and what is that worth to you
3. Material: cotton, silk or fleece, which is where comfort is really decided

The most important question is whether you actually need a liner on your trip at all, so it does not become dead weight. The more you will use it, the better the quality you should aim for. Material plays the biggest role for comfort, so let us take the three main options one by one.

Cotton liners

Cotton liners are the only kind I have long personal experience with, and at a guess they are also the most widespread and the most affordable. Opinions differ on when wool or synthetics beat natural fibres on a hike, and the same debate applies to liners.

Cotton scores well on durability, easy washing and temperature regulation. That makes it the obvious long-term choice, and cotton works on both warm and cold nights. Some cotton liners come blended with stretch fibres for more freedom of movement during the night, and some have an antimicrobial treatment woven into the fabric that limits the build-up of odour-causing bacteria. Both features are worth looking for, since a liner gets washed less often on the trail than you might hope.

Silk liners

I have never walked with a silk liner myself, but I sleep on silk sheets at home and love them, so I suspect I would get along with one fine. Silk is extremely comfortable to sleep in, and a silk liner also adds a few degrees of warmth to your sleeping bag. On top of that it is ultralight and packs down to almost nothing in your backpack.

Silk is clearly what I will choose next time I need a new liner. The trade-off is price, since silk liners generally cost more than cotton. Silk also helps regulate body temperature and transports sweat away, which keeps you warm in the cold and cool in the heat. For a warm-weather Camino where the liner replaces the sleeping bag entirely, silk is hard to beat.

Fleece liners

Fleece is generally the material that adds the most extra warmth to a sleeping bag. That also means fleece liners work well on their own without a sleeping bag, or when you are sleeping somewhere genuinely cold. There is a sea of different fleece liners out there, and some use insulating fibre technologies designed specifically to hold extra warmth.

If you see the word “liner” used on its own in shops and wonder about it, that is simply the short international name for the product. If your priority is maximum insulation for cold nights, whether in a mountain albergue or a shelter in early spring, fleece is the material to pick. The cost is bulk, since fleece packs larger than silk or cotton.

Why choose a liner at all?

I have been on countless trips, and most of them were without a liner. If you are considering buying one, it comes down to three good reasons:

1. It will replace your sleeping bag on a warm-weather trip
2. You need extra warmth inside your sleeping bag
3. You use your sleeping bag very often

Sleeping bags do not respond well to washing. With a liner between you and the bag, you avoid the bag turning clammy and worn, and you dramatically extend its life, because the liner takes the washing instead.

I have been happy with my liner on the Camino in summer, but in general I prefer to bring either a liner or a sleeping bag rather than both, since I am a big believer in the minimalist packing style. I still manage to overpack anyway. Electronics, a full-size towel, the lot. These days a microfiber towel has replaced the big one, which alone freed up a surprising amount of space.

I hope this guide helps you arrive well prepared. If you are heading out on the Camino or another outdoor trip, use the packing advice in my guides as inspiration before you zip up the pack. Buen Camino!