When to Use A Sleeping Bag Liner


When you’re camping in the mountains the weather can change quickly- even in the summer.  A nice warm bluebird day can suddenly turn to sub-zero temperatures, at certain elevations.  Having the right gear, like a sleeping bag liner can keep you warm when your sleeping bag isn’t up for the challenge.  For the blog, I’m going to explain when to use a sleeping bag liner, the various types of liners and my favorite liner brands.

A sleeping bag liner is intended to add warmth or versatility to your sleeping bag. A liner is another layer of warmth on those extra chilly nights.  When it’s extra warm outside, a liner can be used in place of your sleeping bag. Liners come in a variety of fabrics and thicknesses, to meet your specific needs.

Table Of Contents

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Sleeping Bag Liner 101

Bedsure Sleeping Bag Liner
Bedsure Sleeping Bag Liner

If you enjoy trekking high into the North Cascades, the Rocky Mountains or Yellowstone you know a thing or two about how quickly temperatures can change. One minute you’re soaking in the sun rays, the next you’re taking cover from a random hail storm. When you’re in the great outdoors, you have to be prepared for just about anything and any weather conditions.  Being prepared means having the right sleeping bag to match your adventure.

So, what does that mean? As you know there are three different types of sleeping bags: summer rated bag, three-season, and winter bags.  Summer rated bags keep you warm in temperatures above 35 degrees, three-season bags keep you warm in temperatures between 10 and 35 degrees and winter bags keep you toasty when the mercury drops below 10 degrees.  Once you select you’re sleeping bag you’re ready for camping! Not so fast. These temperature ratings are general guidelines.  Your metabolism, tent, weather and other factors play a role in how warm or cold you will feel.

Because there are so many variables in determining how comfortable you will be inside your sleeping bag, it’s a good idea to have options.  Sleeping bag liners, such as this Bedsure Sleeping Bag Liner in the above left picture, give you the option of adding warmth, insulation, and comfort right away, right inside your tent or under the stars.  There’s an old saying in survival training: it’s easier to stay warm then it is to get warm. A sleeping bag liner will keep you warm- when your sleeping bag isn’t cutting it. Sleeping bag liners are also great for travelers who are staying in hostels, campgrounds or hotels.

Sleeping bag liners fall into two categories: mummy shaped liners and rectangle liners.  Mummy shaped liners are designed to slip right into your sleeping bag. The mummy shaped is designed for backpackers who need extra warmth and comfort while deep in the woods.  Rectangle shaped liners are designed to be used alone, as a top bed sheet at a questionable hotel or hostel. These liners can also be used while camping when it’s simply too hot and uncomfortable to climb into a sleeping bag.

Types of Liners

Coleman Stratus Adult Fleece Sleeping Bag Liner
Coleman Fleece Sleeping Bag Liner

If you’re in the market for a sleeping bag liner, you probably realize there are a lot of choices. The perfect liner for one person, may not work for another.  The best liner will be the one that matches your activity level, sleeping style and where you will be setting up camp and the weather.  Sleeping liners are available in five materials: silk, cotton, fleece, synthetics and insulated.  Some liners are made with bug netting to keep the mosquitoes away while you camp alongside a river in July. In the picture on the left is an example of a fleece liner: Coleman Fleece Sleeping Bag Liner

Cotton liners are the least expensive of sleeping bag liners.  Cotton is cheap and durable. While cotton feels cozy and soft, it can actually make you colder. Hear me out.  If you are camping in cold weather, it’s best to leave all cotton at home. Seriously, don’t even wear cotton socks and underwear. When cotton gets wet, it has the ability to retain water like a wet sponge. So, when start sweating- that moisture stays in the shirt. The cotton then draws body heat away from you.  If you tend to sleep hot or sweat during the night, a cotton liner may not be the way to go.  Cotton would probably be just fine for summer camping.

Silk is an excellent material for both winter and summer camping. Silk is smooth, cozy and lightweight.  Silk also has the natural ability to keep moisture away from your body.  If you want to invest in one sleeping bag liner for all seasons, a silk-based one will do the trick. Fleece is another great option if the mercury dips lower then you expected it to.  Fleece is soft, comfortable and adds 12 degrees of warmth to your sleeping bag. How about that? If you sweat during the night, the fleece will naturally wick away all that moisture.  Fleece also dries quickly too- so no need to worry if you spill a bottle of water or end up in a river. A fleece sleeping bag liner is a great choice for fall and winter camping.

Insulated sleeping bag liners are designed to add up to 25 degrees of warmth inside your sleeping bag. Insulated liners are lightweight and are made out of Thermolite fabric. This fabric is designed to capture your body heat and keep it where it belongs- right next to you. An insulated liner is just what you want to take with you when you’re heading into the mountains in late October or early March.

Synthetic sleeping bag liners are made out of a polyester/nylon blend. This material is excellent at keeping your body heat right next to you and moving moisture away. Synthetic materials wick away moisture to keep you warm and dry all night long.  Some synthetic liners have a lyrca too, which gives you a little movement when you are tossing and turning all night. Depending on the brand, synthetic liners can add up to five degrees of warmth. This is a great liner for spring and summer camping- when you need just a little extra layer, but not too much!

Insect repelling liners are a great choice if you are camping during the summer months and are concerned about flies, ticks, and mosquitoes.  These liners are made out of polyester and have a built invisible shield, to keep those pests at bay. Not sure exactly is in the material to keep bugs away, but according to reviews, it works. This type of liner is best for summer camping. It can be used alone or in a sleeping bag.

One Bag: Four Seasons

Spring Season
Spring Season

A high-quality sleeping bag is an investment.  Depending on the type of bag, you can easily spend more than a thousand dollars on a single bag.  If you like to hike, camp and fish year-round, chances are you aren’t going to want to buy a new sleeping bag every single season.  A sleeping bag liner allows you to use your sleeping bag every season of the year.  With a liner, you can use your three-season bag, four seasons.  You can use a summer bag in the winter.  You get the point.

A sleeping bag liner, however, will not make it easy to use a winter bag in the summer.  Perhaps you can sleep on top of your sleeping bag for comfort and have a liner on top so you don’t get too hot. Even if you buy four liners for your sleeping bag, it’s still less expensive than buying four sleeping bags to match every possible weather scenario you may encounter during the year.

Depending on the brand, sleeping bag liners will cost you anywhere between $25 and $80. When you consider a quality sleeping bag is easily a couple hundred dollars or more, it’s worth it to buy a couple liners.  In addition to making your sleeping bag more versatile, liners also extend the life of your sleeping bag. Liners keep your bag clean and protect the seams inside your bag from wear and tear.  Washing a sleeping bag is a lot of work and it can reduce the insulation value in some cases. I still remember that time I washed a down insulated sleeping bag, only to have feathers everywhere.  There goes the insulation! Using a liner will keep dirty feet, sweat, and food even reaching your nice, cozy and expensive sleeping bag.

Liners for Traveling

Traveling Camping
Traveling Camping

A sleeping bag liner isn’t just for camping near an alpine lake in the middle of the wilderness. A liner is a great thing to pack with you the next time you travel around Europe, Asia or Italy. If you’re globetrotting anytime soon, pick up a sleeping bag liner to take with you- even if you aren’t using a sleeping bag. A liner will protect you from bed bugs at questionable budget hotels and add a layer between the hostel cots and your head.

Sleeping liners are designed to be used almost like a bed sheet.  If you are traveling during warmer months, you can use the sleeping liner like you would a sleeping bag. An insect shield liner is a great choice if you are camping outside while on your adventure.  Silk is another affordable travel liner. Liners designed for travelers are easy to hand wash or throw in a washing machine in between use. A sleeping bag liner will also give you peace of mind when the only bed in town is a budget hotel, that looks a little sketchy.

Top Liner Picks

Cocoon Merino Wool Mummy Liner
Cocoon Merino Wool Mummy Liner
Cocoon Merino Wool Mummy Liner

The Cocoon Merino Wool Mummy Liner is a high quality, durable and incredibly comfortable sleeping bag liner. The mummy shape makes this liner perfect for backpacking! The liner is made out of 100% merino wool, making it great for added warmth and keeping moisture away. It is really quite a slick sleeping bag liner.  Merino wool is soft and cozy, adding comfort while camping under the stars or inside a tent. This bag is rated to add about 10 degrees to your sleeping bag and retails for $99.

Sea to Summit Thermolite Reactor Liner
Sea to Summit Thermolite Reactor Liner
Sea to Summit Thermolite Reactor Liner

If you are looking to add extra warmth to your summer or winter sleeping bag, the Sea To Summit Thermolite Reactor Liner is the liner for you. This liner is made with thick microfleece- making it equally warm, soft and comfortable. The liner adds a whopping 32 degrees of warmth to your sleeping bag. In fact, you could take a summer bag and be comfortable in sub-zero temperatures with this liner. The liner can also be used alone during those brisk summer evenings and mornings. This liner retails for $80.

Cocoon CoolMax TravelSheet
Cocoon CoolMax TravelSheet
Cocoon CoolMax TravelSheet

The Cocoon CoolMax TravelSheet is great for travelers. This liner is made with lightweight soft and smooth silk. It can be used in two ways: one side is made of silk, the other is made with thermolite.  So, it’s an insulated liner and a silk liner in one. The liner can add up to 10 degrees to your bag, depending on how it’s used. If you use the silk side alone, as a travel sheet it will not add any additional warmth- just protection from when you have to sleep on the ground or in a shady hostel. This liner retails for $65.

Sea to Summit Coolmax Insect Shield
Sea to Summit Coolmax Insect Shield
Sea to Summit Coolmax Insect Shield

If you spend a lot of time in the back-country or camping by a lake, you know how relentless the bugs can be. When you are trying to get some shut eye, the last thing you need is a mosquito buzzing around your head. The Sea To Summit Coolmax Insect Shield sleeping bag liner is designed to keep bugs at bay while you drift off to dream land. The bag has an invisible bug shield infused into the soft and cozy fabric.  According to the manufacturer, this liner is like sleeping in your favorite vintage t-shirt. You know that old Rolling Stones t-shirt that is so soft, you wear it every weekend? Yep. Just like that.

The liner is available for mummy bags and for the traveler. This liner retails for $63.  Sea to Summit is one of the best brands for sleeping bag liners.  No matter where your next adventure takes you, a sleeping bag liner will make it more comfortable and enjoyable.

See also “What Are The Best Sleeping Bag Brands?“.

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