Why campers love down sleeping bags

By Sea to Summit


Down is one of the oldest insulations around—and yet it’s still arguably the best.

It’s also one of the most misunderstood materials. Most people consider down insulation the best out there but when faced with a room full of ‘loft ratings’ and RDS-certified Hydrophobic Down sleeping bags… things can quickly get overwhelming.


Down sleeping bags offer the best ratio of warmth-to-packability, making them a favourite of lightweight campers everywhere.

A quality down sleeping bag is an investment—so it’s great to understand what you’re paying for and relying on out in the wild.

Down is the fluffy clusters found underneath the feathers of waterfowl. Each cluster has thousands of tiny fibres that trap air and heat.


When we talk about down, we’re talking about the fluffy clusters found underneath the feathers of waterfowl—their natural insulation. Each cluster has thousands of tiny fibres that trap air and heat.

But when you purchase a down sleeping bag, it’s normally filled with a combination of these clusters and feathers. It’s not that we’re scrimping on the good stuff, the feathers are there to provide a little extra structure so the soft down clusters can fully loft under the weight of the shell materials (light as they may be).

Why choose down?

No other material comes close to the performance, longevity, compactness and breathability of quality mature down. Though synthetic sleeping bag insulation is constantly upping its game.


Three one-ounce canisters of 650+, 750+ and 850+ Loft down.
Above: one ounce of 650+, 750+ and 850+ Loft down

Loft rating and fill-power are the same thing, the latter being the more popular term in the US.

The fluffier a cluster of down is, the more air and, thus, heat it can trap. The higher the ‘loft’ or ‘fill power’ of your down sleeping bag, the better its warmth-to-weight ratio. A bag filled with high loft down will be more compressible than a similar temperature bag with a lower loft/fill-power.


The longer a down bag is stored in its compressed state, the longer it will take to spring back to its natural loft (which it will, if you don’t ruin it with chemicals or heat). Conditioning with steam will speed up the process considerably.

Is a high loft down warmer?

Not always. A higher loft number (or ‘fill power’) down isn’t necessarily warmer. It just means that you need to use less of it than a lower-rated down to achieve the same warmth. A 600+Loft can be as warm as an 850+Loft bag but it won’t be as light or compressible.

Our down sleeping bag range and other down products range from a 600+Loft to 850+Loft. To calculate this rating, a one-ounce sample of down is compressed and then allowed to expand in a special cylinder. The total volume the down expands to (measured in cubic inches) makes up its loft number. That means that a 750+Loft down would fill at least 750 cubic inches.


850+ Loft Down Sleeping Bags
750+ Loft Down Sleeping Bags
650+ Loft Down Sleeping Bags


Down is a serious business and so independent bodies—like the IDFL Laboratory and Institute and the Responsible Down Standard—keep the industry in check.

Fill weight in down sleeping bags

If you’re paying for it, you deserve to know how much down you are buying. Fill weight is simply how much down has been placed inside a sleeping bag.

Our sleeping bags, for example, have a hangtag that specifies how much down is in your sleeping bag—as well as handy things like dimensions and EN ratings.

IDFL Institute and Laboratory

All of our down at Sea to Summit is tested by the IDFL (and our own labs) for over 30 qualities including fill power, cleanliness, hydrophobic quality and down-content ratio. This certificate is then provided with all our down sleeping bags. As far as we know, we’re one of the only companies to do this.

Responsible Down Standard (RDS) Certification

RDS Certification is a safeguard for the humane treatment of the geese and ducks that provide down. The certification process requires third party audits of all aspects of animal rearing and handling through to the finished item and the correct labelling of products.

Keep an eye out for RDS Certification when you purchase your next down product to ensure inhumane practices—such as force-feeding and the removal of down from live birds—are completely stamped out of the industry.

Which type of down is best?

Tough call. Many types of down can produce great sleeping bags. And a sleeping bag is more than the sum of its down fill—design goes a long way to maximise the warmth and comfort.

If your sleeping bag has an 850+Loft down, it should be lighter and more compact than a similar bag that uses 750+Loft down. Perfect if you’re an ultralight camper.

If you use enough 650+Loft down, you can achieve the same EN temperature rating as the 850+Loft, but you’re going to be carrying around more bulk and weight. It’s up to you how much your sleeping bag can weigh. Sometimes a few extra grams isn’t the end of the world. Especially if your van or 4WD will be carrying the load.


There’s more to a down bag than its loft rating. Does the construction of the sleeping bag allow the down to fully loft? Do the baffles keep the insulation where it’s needed? Strategically placing insulation can make a huge difference too.

There’s a lot that factors into a quality down sleeping bag—which is why designing them is never boring.

The baffles in down sleeping bags are designed to control where the down is placed, and to stop it shifting around and creating cold spots. Most of our bags have vertical baffles in the torso and horizontal baffles in the lower half. This keeps the insulation where it’s needed as you roll around in the middle of the night.

The type of baffle matters too. There’s box baffles, sewn through construction, overlapping baffles and more—each suitable for different temperatures. Side block baffles are useful for stopping down moving from the front of the bag to the back (where it can’t loft as well) and draft tubes along the zippers protect you from cold gusts of wind.

Baffle volume is also an important part of the equation. This must be correctly calculated to the volume of lofted down placed within it. Too little room, and the down won’t loft to its full potential. Too much room, and the fill will move around your bag.

Lastly, as we go into full geek mode, directional lofting also plays a part in a good quality down sleeping bag. This is where the shell and lining fabrics are cut in a way that encourages the direction that the down lofts. Our bags are designed in such a way that the down lofts away from you on the top side of the bag. The underside of the bag has been designed for the down to loft into the bag, towards the sleeper. All of this aims to allow the down to loft as much as possible, thus trapping more heat.

Down sleeping bags and wet weather

While down sleeping bags typically out-perform synthetic bags on most fronts, its one downside (pun intended) is that it doesn’t perform well when wet.

Luckily, hydrophobic treatments like ULTRA-DRY Down™ have virtually eliminated this problem. This PFC-free treated down retains 60% more loft, absorbs 30% less moisture and dries 60% faster than untreated down.


Down will not achieve its full lofting potential when bone dry. It needs a moisture content of approximately 11% to achieve maximum loft.


To recap, here’s a checklist of everything to check for when purchasing your next down sleeping bag:

  • The loft rating of the down—so you know how well that product is likely to compress and what you’re paying for.
  • The EN rating (if there is one). It’s still by far the most standardised measurement in the industry and your best chance of finding a sleeping bag that will keep you warm enough.
  • The weight and packed size. Is it light and compact enough for your use?
  • RDS Certification to ensure the humane treatment of waterfowl and quality of the down.
  • Hydrophobic treatments like ULTRA-DRY Down™. You’ll thank yourself on a rainy day.
  • Independent certification (like IDFL) that tests for the quality of down.
  • Fill weight. It’s good to know how much down you’re getting in each product so you can compare.
  • Then there’s are a few other factors to consider when choosing a sleeping bag—from fit and materials to anti draft features.


Besides its technical performance and impressive weight-to-warmth ratio, another benefit of down is its longevity when properly cared for.

Washing and drying your down sleeping bag, for example, is a great way of improving warmth and comfort.