How to Store a Down Sleeping Bag to Avoid Clumping?

Have you ever experienced “cold spots” in your sleeping bag? Clumping causes them and clumping may be caused by suboptimal storage of your bag.

Gear can get expensive and no one likes to ruin their equipment by storing it the wrong way. Despite that, I see quite some debate in the online hiking communities on how to properly store a down sleeping bag.

By compressing a down sleeping bag, the down feathers clump together and slowly lose their volume, especially if stored in humid and warm conditions. It is essential to never store a down sleeping bag fully compressed and to make sure it is completely dry and clean before packing it away long term.

The ability of a down sleeping bag to keep you warm is determined by the volume or “loftiness” of the contained down feathers.

Indeed, by understanding the mechanics of down fibers and following the simple guidelines outlined in this article, your sleeping bags lifespan and performance will increase dramatically.

How does down filling differ from synthetic filling?

Before we jump into the fluffy facts of down compression mechanics, it is important to know the difference between natural and synthetic fibers – the two materials used as insulators in sleeping bags.

Synthetic filling is made from thin threads of polyester – a man-made material that does not collapse to the same degree when wet and has a higher tolerance to heat. Read more about the properties of polyester here.

The composition of a down unit is much more voluminous and delicate than that of the homogenous synthetic polyester filling used in cheaper sleeping bags.

Feathers, down included, are made up of a protein called “keratin”. This is the same material that makes up our nails and hair as well as the horns, scales, and wool of animals.

The physiochemical behavior of keratin is highly dependent on humidity (hydration of the protein), and temperature. The higher the moisture content and temperature, the less elasticity and strength it has.

While synthetic materials tend to do better because they don’t experience the same entangling and deformation of the fibers upon compression, the down filling tends to deform and clump more easily resulting in a lower tolerance to long-term compression,

The downside of synthetic filling, however, is that polyester is heavier per volume and therefore has a much lower fill power compared to down.

You just don’t get the same high insulation ability from synthetic materials, and you will therefore need to use much more of it, which compromises the weight of your bag.  

Why is Compression Bad for a Sleeping Bag?

Compressing a down sleeping bag helps to reduce its size and can be handy when traveling – this is one of the great properties of down!  

However, most experienced hiker’s advise against compression since it might lead to lower performance of your sleeping bag.

You have probably heard that you should not compress a sleeping bag for too long if you want to stay warm when using it. So why is this exactly?

Down sleeping bags can fluff up after being compressed, but there is a limit to their resistance to compression.

The mechanics behind this phenomenon lay in the structure of the down feathers.

So as mentioned, the proteins of down fibers are identical to the ones of human hairs. So you may think of feathers as thick hairs branched with ultra-fine hairs.

And what happens if you wear a hat, and compress your hair, for extended periods of time? Your hair gets flat or messy!

This is the same for a down sleeping bag.

And what happens to hair that gets wet? It clumps together and it feels cold.

This is a problem that woolen animals such as sheep have evolved solutions to by secreting lanolin compounds that repel the water away from the keratin fibers to prevent collapsing the insulating structure and discourage bacterial growth leading to odors.

Luckily, most sleeping bag manufacturing companies these days treat their down filling with a DWR component to prevent the effect of water on clumping.

Not only is the surface of most modern sleeping bags waterproofed by DWR, but the downs are treated in the same way to make them more resistant to water. Read more in my review of the Naturehike CW300 sleeping bag.

The worst outcome arises when you combine moisture and compression – think about the effect on your hair when wearing a hat or helmet right after showering!

This is the same with down in a sleeping bag. This is why you really want to avoid getting your sleeping bag wet as it will drastically reduce its insulation ability.

Heat also plays a role, as the higher temperature decreases the strength of down’s keratin fibers in the same manner as humidity does. Therefore, a hot and humid sleeping bag loses its loft and therefore its insulation power.

The “lofting” ability of down, is also known as fill power (measured in “cuin”), and it is the key to a sleeping bag’s insulation. A “fluffy” sleeping bag helps trap body heat. That’s what keeps you warm, which is why you should preserve it.

And just as woolen clothing that shrinks when washed at high temperatures, too much heat may in fact permanently damage the loft of the down by shrinking and entangling its keratin fibers!  

Can you over-compress a down sleeping bag?

Yes, the more you compress your down sleeping bag, the more likely you are to inflict permanent deformation of the down. Over compression is especially detrimental when the bag is stored in humid and warm conditions.  

No matter how good the quality of your down sleeping bag is, you should always pay attention when compressing it.

Over-compression is a possibility and will visibly shorten the lifespan of your gear. While it is not a problem when camping and pulling your bag out every night, it is an issue when storing the bag between hikes.

This is the reason why all manufacturers and producers of sleeping bags always recommend avoiding long-term storage of your sleeping bag compressed.

And even the down bags from cheaper brands such as Natuehike and Aegismax provide a large storage sack (5-10 times the volume of the stuff sack) intended for long-term storage.  

With time, no matter how careful you are, your bag will eventually clump, which results in an uneven distribution of insulation.

How to Fix a Clumping Sleeping Bag?

If you are in the unfortunate situation that you already have compromised the quality of your down – don’t worry, there may be a way to fix it!

The severity of clumping may depend on whether the clumping is due to compressing the sleeping bag for too long, from washing it in the wrong way, or simply from many years of repeated use.

In the latter case where the sleeping bag is simply worn out, I would just recommend buying a new sleeping bag as you can get really good and cheap (around 100$) down sleeping bags.

However, if the sleeping bag is relatively new, it may be worth spending some time and energy on untangling the clumped down and there are generally two ways to do this:

  1. Tumble drying the bag at low heat (less than 50 °C or 120 °F) for several hours with 2-4 tennis balls.
  2. Air drying the sleeping bag and manually “massaging” and shaking apart the clumps.

The former method is more effective but also subjects the sleeping bag to more wear and tear than the “cold” manual method.

Also, be careful that the synthetic material of the sleeping bag does not come in direct contact with the heating element as it may melt and rupture the bag.

Make sure the tennis balls don’t get stuck in the sleeping bag, as this will prevent even distribution of the down. Golf balls or other not too heavy round and sturdy objects may also be used if more convenient to you.

The process of fixing clumping is also relevant when washing your bag, and is essentially the same as explained in the second part of the video.

For the manual “massage separation” method it is very important that the down is completely dry and unfolded so this one is best done in a dry and cold climate e.g. in the wintertime.

I have also had success with a combination of the two methods, where you start out with a few hours in the dryer interrupted by some manual separation towards the end of the run.

For how long can a down sleeping bag be compressed?

Usually, it is recommended not to leave your down sleeping bag compressed for more than 12 hours at a time.

Of course, if critical for the storage once in a while when hiking, you can leave your bag compressed for longer, but in the long run; you’ll affect its performance.

Just remember to air and shake your bag through and make sure it is dry before packing it after a long night where feathers have been heated and moisturized by sweat and humidity in the tent.

However, with regular unpacking, such as when used every night on a hiking trip, compression is less problematic.

How much can I safely compress my down sleeping bag?

While there are no clear guidelines about how far you can go with compressing, I recommend not comprising beyond 40% of the unpacked sleeping bag volume. This ensured that the down feathers of the bag do clump and deform even when stored.  

In any case, it is never a good solution to leave a sleeping bag compressed for too long.

To be fair, higher compressing might not be too bad if you do it once or twice for a few weeks. However, the process of compressing and uncompressing will affect the performance of your bag in the long term.

The limits to the compression also depend on the quality of your sleeping bag, the humidity, and the temperature.

I sometimes just fold my sleeping bag a few times and place it loosely in my closet. This is the super affordable down sleeping bag from Naturehike that I recently reviewed.

Since over-compressing is more of an issue in warm and humid conditions, you must always pay attention when storing long term and try not to store your bag outside in the sun or in a humid basement for example.

In general, high-quality down sleeping bags (minimum 90% down plumules and maximum 10% pin feather content with a high fill power) are the most resistant to compression.

Verdict: Should I store my down sleeping bag compressed?

The short answer is: If you can avoid compressing it, better do so! However, there are indeed situations where compression is needed and is totally fine.

The answer really depends on your immediate needs:

  1. Will you need the sleeping bag within the next week or so?
  2. Is the performance or volume of your sleeping bag most important to you?

Storing sleeping bags can be a hassle because of the space they take up. However, do not leave your down sleeping bag longer than necessary. Consider your compression bag only as a means of transport for your sleeping gear.

So let’s be clear: if you want your down sleeping bag to last long, you shouldn’t store your sleeping bag compressed.

Personally, I find that the best way to store my sleeping bags is to hang them in my wardrobe closet.

Most outdoor shops store their bags in this way as well.

Before doing so, remember to give it a little shake and “massage” the material to redistribute the feathers evenly, so they don’t end up clumping together in the bottom of the bag!

Of course, the exact storage conditions suitable for you also depend on how much and how you use your bag.

In most outdoor shops, sleeping bags are stored by hanging, rather than packed down.

Aside from repeating the importance of limiting compressing your down sleeping bag, another tip that might help you is to ensure the equipment is completely dry before storing.

Doing so will help you get rid of sweat, rain, or snow. The best way to dry your bag is to hang it in a dry location, outside overnight if possible, I usually leave it for at least 24 hours before storing it away.

To stay on the safe side, it is best to hang your sleeping bag indoors. However, make sure you always check with the manufacturer’s recommendation you can find on the gear.

If you want to know more about down sleeping bags and read my opinion on some very lightweight and affordable quality down bags, see my latest review.