Gear Explained: Sleeping Bags

With so many sleeping bags on the market, picking the “right one” can seem a daunting task.

My dad and I cozily tucked into our sleeping bags during a cold night on the John Muir Trail.

|| Sleeping Bag: So What Really Is It. . .? ||

I like to describe a sleeping bag like a human thermos. It does not generate heat, but rather, traps heat that your body radiates to the surrounding environment. The various temperature ratings of sleeping bags, such as 30 F, 20 F, etc., measure how efficiently the bag is able to retain heat that your body radiates. Bags that have lower temperature ratings are better at trapping heat and will retain their insulating properties at lower temperatures.

|| Down vs. Synthetic ||

Two types of insulation material are found in sleeping bags, either down (i.e. feathers) or synthetic (such as polyester).

Down Insulation

“Down” insulated sleeping bags have insulation made from animal feathers, most commonly goose or duck down. The numerical rating of “fill power”, such as 650 fill, 850 fill, etc., refers to how tightly packed the feathers are together. The higher the rating, the tighter packed the insulation is, which leads to a greater warmth-to-weight ratio.

Benefits of Down Insulation

  • Down insulated sleeping bags have an incredibly high warmth-to-weight ratio. They are typically much lighter than a synthetic sleeping bag of a comparable temperature rating.
  • With the advent of water-resistant down, down bags are incredibly water resistant, and will keep their insulating properties even when damp.
  • If properly maintained, down bags have a longer lifespan than their synthetic counterparts.
  • Down insulation is typically much more compressible than synthethic insulation, meaning you can pack it down to a smaller volume.

Drawbacks of Down Insulation

  • Down bags are typically more expensive than synthetic sleeping bags.
  • Down bags lose their insulating properties when they become saturated with water. For this reason, down bags are not ideal for humid, wet environments such as the Southeast.
  • Down bags should not be stored compressed for extended periods of time, as they will lose their “loft”, or insulating properties. Ideally, down sleeping bags should be stored loose, either hung on a rack or from a wall hanger, or in a large stuff sack which does not compress the bag.

My Verdict on Down Bags

Before I make any gear purchase, I try to prioritize my needs and goals for the specific piece of gear. For sleeping bags, in particular, some questions that can help direct your product search are:

  • How important is the weight of the sleeping bag?
    • If your sleeping bag needs to be as light as possible, and you are willing to spend a few extra dollars, then down insulation is your way to go.
  • What type of climate will you be travelling in?
    • For dry climates, such as the American West, down bags are ideal.
    • However, for more humid and wet climates, such as the Southeast and Appalachian regions, synthetic insulation may be a better fit. That said, the water-resistant down on the market today performs beautifully in my experience. Just consider that down insulation will lose its insulating properties to a greater degree when wet than synthetic insulation will.
  • What is your budget?
    • As mentioned, down sleeping bags are typically a significant investment. They very easily can become your most expensive piece of gear. Consider how long you anticipate using the bag for, and if it makes sense for you to invest a significant amount of money in a high quality down bag.
  • Can you maintain it properly?
    • As mentioned, down bags must not be stored in a compressed state. Make sure you have space to leave your down bag hanging or in a large, uncompressed sack.

Down Bags I Like

These are just a few examples of down insulated bags that I like.

  • REI Co-Op Igneo Sleeping Bag (REI, $270-$330)
    • I have this bag in 20d and I LOVE IT!! Took it with me on the John Muir Trail and it kept me warm on some cold nights. For warmer nights in the Southeast, I simply unzip the bag and use it like a blanket.
    • Comes in 17d or 25d rating
    • 700 fill duck down
    • Comes in Regular or Long
  • Western Mountaineering Ultralite (Backcountry.com, $485)
    • Western Mountaineering is renowned for their extremely high quality down products. That said, they come with a hefty price tag.
    • 20 F rating
    • 850 fill goose down
  • Mountain Hardwear Phantom Torch 15 (REI, $500)
    • As Mountain Hardwear states, “Gram counting backpackers and climbers will appreciate the lofty warmth of the lightweight and compressible Phantom Flame 15 from Mountain Hardwear.
    • 800 fill water resistant down
    • Weight (regular): 33 oz
    • Volume (regular): 7.6 liters
  • Kelty Cosmic Down (REI, $150)
    • For those of you on a tighter budget, the Kelty Cosmic Down is an inexpensive option. Heavier and bulkier than some of the other bags on the market, it is a great entry level down bag.
    • 600 fill water resistant down
    • Weight (regular): 44 oz
    • Volume (regular): approx. 9 liters

Synthetic Insulation

“Synthetic” insulated sleeping bags are filled with polyester fibers, instead of down feathers.

Benefits of Synthetic Insulation

  • Synthetic insulation, in general, retains its insulating properties better than down insulation when wet or damp. That is, synthetic insulation will keep you warmer when it’s wet than down insulation will.
  • Synthetic bags require less maintenance than down sleeping bags. They can be stored compressed for longer periods of time than down sleeping bags can. However, they still should not permanently be stored in a compressed state.
  • Synthetic sleeping bags are generally much less expensive than down sleeping bags.

Drawbacks of Synthetic Insulation

  • Synthetic bags are generally heavier and bulkier than down bags of comparable warmth.

My Verdict on Synthetic Bags

Again, your gear choices should be based on what your needs and requirements are for your specific adventures.

  • How important is the weight of the sleeping bag?
    • If weight is not a primary concern for you, then synthetic bags will be a much more affordable option, in general.
  • What type of climate will you be travelling in?
    • If you will be travelling in more humid and wetter climates, synthetic insulation is probably a better choice for you than a down bag, even if it has water resistant down.
  • What is your budget?
    • Synthetic sleeping bags are much more reasonably priced than down bags, on average. If you are looking for an entry level sleeping bag just to get you out there, look no further.
  • Can you maintain it properly?
    • If you are tentative about the care required to maintain a down bag properly, a synthetic bag may be a better fit for you.

Synthetic Bags I Like

  • Mountain Hardwear HyperLamina Spark (REI, $220-235)
    • “Winner of Backpacker magazine’s 2015 Editors’ Choice Award”
    • 32 F rating
    • Weight (regular): 28 oz
    • Volume (regular): 5.6 liters
  • The North Face Hyper Cat 20 (REI, $240-250)
    • 20 F rating
    • Weight (regular): 30 oz
    • Volume (regular): 11.5 liters
  • Marmot Trestles (REI, $99-160)

|| Additional Considerations ||

As with almost any piece of gear, you need to make sure that the sleeping bag works for YOU. Just like a pair of shoes or boots, I highly recommend trying sleeping bags “on” in store, as the fit for each one is different.

Be Careful About “Roominess”

Remember: A sleeping bag is like a human thermos, it heats up the air trapped between you and the bags walls. If you have a sleeping bag that is very roomy and has a lot of airspace, it will take longer for you to feel warm. Ultimately, how tight you want your bag to feel is your own personal decision, just understand that there are trade offs between wiggle room and how quickly the bag will “warm up.”

A Common Mistake: Wearing Layers in Your Bag

A common  misconception I have witnessed: “if it’s colder, I should wear an extra jacket in my sleeping bag to keep me warmer.”

My response, “well. . . not quite.”

As I’ve said numerous times, a sleeping bag is like a human thermos. So are other layers of insulation, such as a jacket or sweatpants. They, in effect, trap a layer of air between your body and the insulation, which your body then heats, making you feel “warm.”

While at first this may sound backwards, you do NOT want to go into your sleeping bag with a jacket or other layers on. In effect, you will  be putting a thermos inside another thermos. Your jacket will trap the heat radiated by your body, preventing you from warming up your sleeping bag. Eventually, enough heat will radiate through the jacket membrane to heat up your sleeping bag, yet it will take a long time.

My tip: Even if it’s cold, “pre-heat” your sleeping bag by going into your bag only with your base layers on. While you may be cold at first, your body will be able to heat up the airspace in your sleeping bag much faster than if you had a jacket on. Once your bag has been “heated,” then you can put on extra layers if you are still cold.

Cleaning Your Bag

Just like a pair of clothes, your sleeping bag needs to be washed from time-to-time. Each sleeping bag has a different set of instructions in terms of washing, but in general, both synthetic and down sleeping bags can be washed in the following ways:

  • Most sleeping bags can be washed in a typical front-loader washing machine. Use the gentle cycle and warm water, along with a proper soap for your bag.
  • For Down Sleeping Bags: do NOT tumble dry. Hang dry. (note: this is a personal opinion. I know some websites say to tumble dry low/gentle.)
  • For Synthetic Sleeping Bags: Tumble dry low/gentle, Hang dry.

Be mindful that while washing your bag is necessary from time-to-time, the process of putting the bag through the washing machine will likely decrease the lifespan of your bag slightly.

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