Down vs Synthetic Sleeping Bags & Jackets (Insulation Guide)

Updated: March 26, 2023

There is much debate about which insulation is better: down or synthetic. Both are comfortable, durable, warm and have their own supporters, so it is hard to know which is the best choice for yourself.

Whose insulation has more advantages and less downsides: the one by Mother Nature or the Man-Made one? Let’s take a look.

Synthetic, Down & Hybrid Insulation Guide

Types of Down Insulation

What is Down?

Down comes from the soft, fluffy undercoat that lies beneath the tougher feathers at the underbelly of a bird – one of nature’s finest insulators. This is also known as the plumage of a bird, and a single plume’s structure creates pockets of air that trap heat and stay warm.

The two most common types of down are duck and goose.

Duck down is more available - as it is more widely consumed - and this makes it slightly cheaper. But, although it is still warm, it is not as fine as goose down.

Goose feathers are bigger and have slightly better insulating qualities than duck feathers, which is why the former tends to be more expensive.

Down in Sleeping Bags

One of the biggest perks of having down insulation in a sleeping bag is that it’s very compressible.

You can easily stuff a below-zero degree sleeping bag into a compartment of your hiking backpack. High-quality down is also extremely light, making it ideal for backpackers.

Because of its natural sourcing, a notable con is that down sleeping bags tend to be very expensive. They also lose all of their insulating abilities when they get wet.

This is something to be aware of if you are sleeping in damp or even dewy conditions, as tent floors can produce moisture that can seep into your sleeping bag.

Down in Jackets

There are two types of down jacket constructions:

  • Sewn Through: Most common and generally the cheapest type.
  • Box Baffle: Which maximises the loft (insulation thickness) and warmth of down fill.

    These are thicker and warmer, but more expensive.

    In general, down’s light weight and compressibility makes for comfortable, portable jackets. It has a wide comfort temperature range – meaning it is suitable for both cold and warm weather – and therefore is a versatile jacket to own.

However, as down loses all its insulating ability as soon as it gets wet, it makes it a pain to use during a rainy winter season or while hiking in the mountains with unpredictable weather and humidity levels (which is when you most need a jacket).

Another downside is that it requires special cleaning, so you can’t just throw it in a washing machine.

Weather and Altitude Conditions - Down Insulation

Not all down insulation is made equal. Every down product has a fill power, which is the measure of ‘fluffiness’ of its insulating properties. Higher fill power means more air pockets in the down and the better its weight-for-warmth insulation.

A fill power of 400-450 is average, while 750-900 is excellent. The higher the fill power, the colder conditions it can help you endure for its weight.

Down is not ideal for rain or damp conditions as it loses its warmth the moment it gets wet. You should also be wary in windy conditions because if you get a rip in your jacket or sleeping bag you will be faced with hundreds of precious feathers flying away and lose most of the insulation.

Down: Cost vs Performance

Down is more expensive than synthetic insulation, and higher fill power will make it even pricier. It is much better quality though, and its durability will make it last you several years.

People who pay the extra penny for a down product are generally very satisfied and believe it to be worthwhile.

Types of Synthetic Insulation

Synthetic insulation is manufactured to create clusters of superfine fibres that result in lots of tiny heat-trapping air pockets. It attempts to mimic down.

The three main types of manufactured synthetic insulation cluster-fibre consist of a bunch of tiny fibre balls than mimic tuffs of down; short-staple which is made up of little, short fibres that move independently; and continuous-filament which is made of continuous filament that intertwines with itself, creating a mass of insulating fibres.

One of the most confusing aspects of purchasing a synthetic sleeping bag or jacket is which type to choose. So here are some of the most common types:

  • PrimaLoftLoft refers to the thickness of insulation. PrimaLoft is extremely breathable, compressible, lightweight, holds heat effectively and has a down-like softness. Its biggest perk is its permanent water-resistance. It is considered to contain one of the best weight-to-warmth ratios available.
  • Polarguard: Made of long-staple fibres that, when sewn into sleeping bags or jackets, is insanely durable and maintains its loft when wet. There are several types of Polarguard, including Polarguard 3D (which more closely resembles soft down). 
  • Polarguard HV (25% lighter and more compressible than other Polarguard variants) and Polarguard Delta (lighter, more heat-retentive and more durable).
  • Climashield: Made of very fine continuous filament fibres that make it extremely durable. It is considered to be one of the most compressible, warmest and softest insulations today.
  • MicroLite: Fibreglass insulation that is super lightweight while staying notably resilient. Fibreglass insulation is the most widely used insulation and is in many products that require temperature control.
  • ThermoLite: Uses a hollow-fibre design, resulting in lightweight, durable and incredibly warm insulation that’s popular among trekkers. ThermoLite Extreme is designed to have the best weight-for-warmth and durability than any other ThermoLite variant. Otherwise, ThermoLite Extra most resembles down, ThermoLite Micro is the least bulky and most compatible, and the ThermoLite Plus is the best designed for extreme conditions.
  • ThermoLoft: This material appears less popular than ThermoLite. It is made of polyester fibres and high-loft Quallofil fibres, and although still effective, it provides slightly less heat and down-resemblance than PrimaLoft.

Synthetic Insulation in Sleeping Bags

While synthetic insulation mimics down’s natural lofting ability, it is yet to match its compressibility and durability. A synthetic sleeping bag will not pack nearly as nicely as down, and its low weight-for-warmth rate will negatively impact backpacking.

But unlike down, synthetic insulation can remain warm when wet, and this is what draws most of its supporters. It is also cheaper while maintaining great insulation qualities.

So, if you aren’t planning to backpack or there’s a high potential that you’ll get wet, a synthetic sleeping bag is definitely worth your while.

Synthetic Insulation in Jackets

The lack of compressibility and weight isn’t as big a priority for a jacket.

But two main perks of getting a synthetic insulated jacket as opposed to a down one are that it still insulates when its wet and dries a lot quicker, making it hassle-free in rainy seasons.

Plus, it doesn’t require special cleaning, so you can throw it in the laundry basket with the rest of your clothes. A synthetic insulated jacket is generally considered a more practical investment as it is cheaper and more manageable for frequent wear than a down jacket.

Weather and Altitude Conditions - Synthetic Insulation

An advantage of synthetic insulation is that it stays warm while it's wet. Because of this, it is best to pick this kind of insulation over down if you’re likely to be trekking through wet or even damp conditions. 

It is also a safer option in windy conditions as a rip wouldn’t have the same consequence as down insulation (i.e. your insulation won’t fly away).

Synthetic: Cost vs Performance

Synthetic insulation is cheaper than down, and although it’s not as high quality, it gets the job done.

The only things you should keep in mind before investing in a synthetic insulated sleeping bag or jacket is that synthetic insulation is heavier and much harder to pack. Otherwise, synthetic is a popular choice among outdoor junkies.

Types of Hybrid Insulation

In Sleeping Bags

Some sleeping bag designs certainly use the best of both insulation worlds. Hybrid designs will place synthetic insulation on the bottom (as moisture builds up from tent floors, and this provides a waterproof base) and down in the top (as it better captures rising body heat).

This results in a product that is cheaper than down sleeping bags, but with a higher warmth-for-weight ratio than synthetically insulated bags.

Hybrid Insulation in Jackets

Hybrid insulation is a growing technology in the insulated jacket market.

They come in a variety of styles, with some jackets mixing the down and synthetic insulation within the jacket, and others using both types separately, to improve range of motion (a down jacket with synthetic sides feels less ‘puffy’).

The perks of a hybrid jacket are that it is lighter and higher quality than a synthetic insulated jacket, yet cheaper than a down jacket, and it can handle damp weather.

Weather and Altitude Conditions - Hybrid Insulation

Because hybrid insulation gets the best of both worlds, it's a safe option for multi-weather conditions.

It is more waterproof than down and warmer than synthetic insulation, however, if your product uses both materials separately (i.e. synthetic lining alongside down lining, instead of a combined lining), take precaution against the wind.

Because down is feathers, they will go flying all over the place if you happen to tear into a section of your jacket or sleeping bag that contains purely down.

Comparison of Down, Synthetic and Hybrid Features


Although synthetic insulation works to mimic down, technology is yet to perfect it.

Synthetic insulation is bulky and heavy when compared to down, and down is even lighter still with a higher fill power. As fill power is calculated by how many cubic inches one ounce of down fill, a 900 fill-power means that one ounce of that down fills 900 cubic inches of space, ergo the higher the fill power, the lighter the product will be, while maintaining the same insulating properties.

When it comes to compressibility, down trumps synthetic. Because of its soft, malleable nature, you can pack a down sleeping bag into your backpack as opposed to clipping it on.

When this is considered alongside its being lightweight, a down sleeping bag is highly recommended over a synthetic for backpacking.


It may come as a surprise, but synthetic is the most breathable between the two insulations. Down traps body heat and keeps it there to create its effective insulation, and because synthetics aren’t as good at trapping heat, they breathe much more.

This becomes obvious when one does a strenuous hike in a down jacket, as they will overheat quite quickly. In a synthetic insulated jacket, it isn’t as obvious, because it regulates body heat so that it never seems too hot or too cold. But a good synthetic jacket will keep you warm while still allowing adequate air to escape.

It is because of this breathability that some argue that synthetic jackets are better for strenuous activities such as biking, climbing, running, ski touring, etc..

Yet synthetics are heavier than down, which makes them more of a pain to carry out such activities. This is why some argue that down’s light weight works better.

In the end, it is up to personal preference – one can either have a breathable but bulky synthetic or a lightweight but potentially overheating down.

Wind- and Moisture-Resistance

Potentially the biggest selling point of synthetic insulation is that, unlike down, it stays warm even when it’s wet. When down gets wet, it soaks up the water and clumps together, making it lose its loft and, as a result, all of its insulation.

This means that if you’re camping and your sleeping bag happens to get rained on, you can expect a freezing night ahead. It also means you have to watch out for tent floor moisture and morning dew.

If you can’t part with the idea of a down jacket, though, you can always purchase a waterproof shell to wear over it as a precaution or hunt for waterproof down jackets.

Synthetic insulation does not soak up water in the same way and therefore stays warm in moist environments. In addition to being protected from rain and outside moisture, this quality also means that synthetic jackets don’t become besieged with sweat on the inside.

This is a contributing reason why synthetic jackets are best suited for strenuous activities.
Both types of insulation protect users from the wind.

But one should take precaution with a down sleeping bag or jacket in the wind, as one rip will send your insulation floating away in a feathery chaos.


Synthetic insulation tends to lose its form after a while and the fibres break down over time, especially if you compress it often. 

Because there are so many different types, though, it is hard to pinpoint how durable they are generally.

Likewise, down can leak over time and therefore lose its insulating quality, and its loft can also be damaged if you leave it compressed for too long.

In either case, correct storage and proper treatment are key for the product lifespan. Cleaning jackets can remove harmful oils and dirt, while placing a silk liner in your sleeping bag can prevent body oils from contacting the fibres.

Generally, synthetic and down insulations will last for the same length of time.

Verdict: Synthetic vs Down Debate

Ultimately, both down and synthetic insulation are comfortable and durable and will keep you warm. In terms of daily use, synthetic insulation is a winner, as it is easier to clean and doesn’t overheat.

It also withstands precipitation and wind better than down. However, downs are of much higher quality, lighter and compress far better than synthetic insulations.


For these reasons, synthetic jackets are a more efficient choice than down jackets. They may be bulkier and heavier, but this doesn’t matter as much in a jacket. 

Synthetic jackets can breathe, unlike down, which means they will stay sweat-scent-free and moderate your body temperature.

Sleeping Bags

On the other hand, down sleeping bags are lighter, more compressible and will keep you warmer than a synthetic sleeping bag of the same (or heavier) weight.

Granted that you keep it dry, a down sleeping bag is worth the extra expense and highly recommended over a synthetic insulated one.


About the author 

Mark Whitman

Mark has trekked extensively in Asia, Europe, South America and Africa. He founded Mountain IQ in 2014 with the sole aim to be the best online information portal to some of the most popular mountain destinations around the world. When not writing for Mountain IQ, Mark is out exploring the outdoors with his wife!

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