Down Vs Synthetic Sleeping Bags – Which is Better?

Sleeping bags are vital for campers of all skill levels, especially when temperatures start to dip below comfortable levels. You’ll often hear people discussing the differences between rectangular sleeping bags and mummy sleeping bags, what they’re good for, and when to use them.

But what about down vs synthetic sleeping bags? It’s a question that’s just as important to consider, though it’s not talked about as frequently. To help you figure out the pros and cons of each, and what might be best for you, here’s the breakdown on these two types of sleeping bag insulation.

Key Takeaways:

  • Down is lightweight, highly compressible, and offers a favorable warmth-to-weight ratio.
  • However, down loses insulative properties when wet, a major concern for damp environments.
  • Synthetic sleeping bags retain insulation when wet, dry faster, and are generally more affordable.
  • However, synthetic bags are heavier, bulkier, and less durable than down bags.
  • The choice between down and synthetic depends on camping frequency, location, and budget.

Down Insulation – Highlights

white feathers

Let’s start with down, my personal favorite, and the insulation that my wife and I have in both of our sleeping bags. It’s the lightest form of insulation, and the most compressible, which makes it a favorite among backpackers. Almost across the board, down sleeping bags are going to be the smallest when packed, giving you more space for other gear inside your backpack.

While down is lightweight on its own, sleeping bags made with it are comparatively lighter than synthetic bags for another reason. The “warmth to weight ratio” is simply a way to gauge how much of a material you need to reach a certain level of warmth. Practically speaking, you need far less down to reach a specific temperature rating than you do with synthetics. This allows sleeping bag manufacturers to cut back on weight and materials without sacrificing warmth and comfort.

Down is also very durable, and less likely to clump, separate, or deteriorate over time. I’ve known many people who have used the same down sleeping bag for decades! In that way, I find that they’re well worth the expense, if you want a bag that will continue to perform well in the long run.

Down Insulation – Drawbacks

Unfortunately, down isn’t without its drawbacks. Some of them are fairly significant, compromising the insulative properties of the material altogether. For example, when down gets wet, it’s completely useless at keeping you warm. This is honestly the biggest problem that most people have with this type of insulation, and it’s a very fair concern, to be sure. If you’re interested in pursuing tarp camping, cowboy camping, or other forms of outdoor living that leave you partially exposed to the elements, don’t get a down bag.

Nowadays, many sleeping bag manufacturers will add a coating of Durable Water Repellent (DWR) to their down. It makes the down hydrophobic, giving it some water resistance, and preventing it from clumping. While it’s still not as effective as synthetics when wet, it isn’t completely worthless either.

The other big problem that people tend to have with down sleeping bags is the price. Down isn’t something that be easily manufactured in a factory like polyester, so by nature, it costs a lot more. And if it happens to be DWR down, you can expect the price to rise even higher.

If you want to avoid the hefty price tag on DWR down, I’d suggest getting a regular down bag and some waterproof spray. Something like the NIkwax T.X.Direct Spray-On Waterproofing is a good option to give your bag another layer of protection against moisture from rain, humidity, or falling condensation. There are other products that you can use from NIkwax that will help you wash you down sleeping bag as well.

One of the last major drawbacks of down is that compressed portions can create cold spots. This is especially true for the parts of the bag that you’re lying on, since your body weight is compacting the down underneath you. There really isn’t much you can do about this, other than add another layer of insulation, like a sleeping pad or a mattress. These are items that I’d recommend having anyway, specifically the Wellax sleeping pad or the Exped MegaMat.

Fill Power

blue and green sleeping bag on the green grass

Fill power is a metric unique to down insulation. It’s used to measure the loftiness (fluffiness) of the feathers, with a higher rating providing more loft. By extension, a higher fill power means that you need less down to reach a certain temperature rating. Which is to say, you can purchase an extreme cold weather sleeping bag with a high fill power, and it will still pack down small and be relatively lightweight.

You’ll notice that fill power is expressed by a number. For example, a fill power of 800 indicates that the one ounce of down will fill 800 cubic inches of space. The best sleeping bags usually have a fill power between 600 and 800, though there are plenty that rank lower than that as well. Generally speaking, I’d avoid going lower than 600 when possible, as anything under that will be hard to compress and won’t keep you warm quite as well.

Of course, as you might expect, sleeping bags with a high fill power go for a pretty penny. But while they aren’t cheap, they’re some of the most effective sleeping bags out there, and will last you a lifetime with proper care. If you can afford it, the mid-three figure price range is well worth it.

Types of Down

Down doesn’t come in just one variety. As you probably know, down is a type of feather, and there are a couple different birds that are used in the harvesting of down. Goose and duck are the most common, so we’ll take a look at the differences between the two, picking out the pros and cons.

Historically, goose down has been used across the board. It’s a great option for sleeping bags because of how well it insulates, with some types of goose down sporting a fill power of 900+. Duck down, on the other hand, is lucky to get as high as an 800 fill power. However, duck down is also significantly cheaper, giving it a great value for price. It’s worth noting that an 800 fill power of duck down is going to be functionally identical to an 800 fill power of goose down. So if you can go with duck, you might as well save a few bucks!

Synthetic Insulation – Highlights

looking outside a tent at yellow grass and snowy mountains

Now, let’s take a look at synthetic insulation and see how it compares to down. In general, I would say that there are two reasons why someone might choose synthetic as their insulation of choice. First, it’s a material that will still keep you warm, even after being soaked with water and/or body oil. This is completely opposite to down, which loses its insulative properties when wet. So as you might expect, someone camping in damp, humid environments is more likely to choose synthetics over down.

Not only does synthetic still insulate when wet, it also dries out a lot faster than down does. In the event that your sleeping bag does get soaked through, you won’t have to wait quite as long to slip into a nice, dry bag for the night. When you’re back home, it also shaves some time off the cleaning process, which is always a win.

Finally, as I briefly mentioned before, polyester fibers are easily made inside of a factory. That being the case, in the debate between synthetic vs down sleeping bags, synthetic is almost always going to come out on top in the price department. For car campers on a budget, synthetic will probably be the way to go.

Synthetic Insulation – Drawbacks

However, the benefits of synthetic insulation end once you get past the price difference and its ability to insulate when wet. And really, hydrophobic down can insulate when wet as well, so the only thing synthetics have going for them is price.

One of the big problems with synthetic insulation is that it’s heavy. A synthetic bag is going to weigh at least a pound or two more than a down bag with an equal temperature rating. It’s also much harder to compress, which means it will take up more space in your backpack if you decide to carry it long distances. In fact, it will take up so much space in your backpack that you’ll barely have room for anything else. These bags aren’t designed for trekkers spending a lot of time on their feet, barring a few exceptions.

The other big problem with synthetic insulation is that it’s less durable. With a down bag, you can expect it to last for decades. Even then, when something does become irreparably damaged, it’s probably not the insulation! Synthetics, on the other hand, will give you about 5-7 years of solid use before it starts to deteriorate. That might sound like a long time to some of you, but do you really want to spend a few hundred bucks on a new sleeping bag every few years? It’s inconvenient and a tough pill to swallow when finances are tight.

Types of Synthetics

campfire at twilight in the mountains with two sleeping bags

Like down, there are two different types of synthetic filaments that you should research before buying. The first one is called short staple, and it was designed to replicate down as closely as possible. It’s made from densely packed, short filaments which provide a lot of flexibility to the sleeping bag. As such, you’ll find that short staple synthetics pack down the best, compressing tightly and folding easily. The tradeoff that you make is a lack of durability, and a little less loft (and therefore, heat retention) in the insulation.

Your other option is going to be continuous filament. Unlike short staple, these filaments are long and have varying widths, weaved together to create a high loft form of insulation. The length and interwoven design also make it far more durable, while preventing cold spots from forming. As you might expect, the extra heft makes continuous filament heavier, bulkier, and harder to compress. Still, it’s the most common type of synthetic insulation out there for a reason: it works really well and lasts a reasonably long time.

Down Vs Synthetic Sleeping Bags – The Verdict

The debate has been raging for decades: down vs synthetic sleeping bags. Which is better? Unfortunately, that question will remain unanswered, because truly, it’s not even the proper question to be asking in the first place. As an activity, camping is so multifaceted that no sleeping bag can fully meet everyone’s needs.

Now, if you ask me for my opinion, I’ll always tell you to go with down. Lightweight, durable, easy to compress, and very warm, you’ll never get me to buy anything else. But that’s just my “backpacker’s brain” talking. From the perspective of a car camper who goes out a handful of nights during the year, a synthetic bag will probably be better for them. There’s no need to go broke by purchasing a sleeping bag that is overkill for what it will be used for. Hopefully this article was able to break down the differences between down and synthetic well enough for you to determine what will be best for you.

Meet the Author!

By the age of 20, Spencer had already tackled some of the most famed mountain ranges in Europe, Asia, and North America. His mission is to help others accomplish their own outdoor-related goals, even within the time constraints of a 9-5 job and a busy life schedule.

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