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Down Vs Synthetic Sleeping Bag Insulation

When choosing a sleeping bag or jacket, one of the most important decisions you need to make is the type of insulation it’s filled with. The insulation (or fill) determines the warmth, price, weight, durability, compressibility, performance in wet conditions, and more. The ideal insulation depends mostly on the climate and temperatures you plan to camp in. There are two main insulation types to choose from. This guide outlines the pros and cons of using a down vs synthetic sleeping bag.

This guide mostly focuses on sleeping bags but most of the info also applies to down jackets, quilts, comforters, and pillows as well.

How does Down and Synthetic Insulation Work?

The goal of insulation in a sleeping bag is to slow heat loss from your body. Down and synthetic insulation function the same way. Both materials consist of many small fibers that loft or fluff up into a unique structure that traps pockets of air. The more loft, the warmer you’ll stay.

As your body heat radiates away, it warms the air pockets between the fibers. The warm air held against your body keeps you warm and comfortable and prevents more heat from escaping. This works because air is an excellent insulator and a poor conductor of heat.

What is the Difference Between Down and Synthetic Sleeping Bags?

The difference between down and synthetic insulation is the material they are made of. Synthetics are man-made and down is a natural product.

Down Insulation

Down is the plumage of waterfowl like geese and ducks. It is a fine, fluffy, and whispy layer of filaments that lie between the bird’s protective outer feathers and its skin. The bird uses its down the same way we use it, for insulation. A common misconception is that down insulation is made from feathers. By definition, the materials are different. Some products use a blend of feathers and down for insulation.

geese on a farm
Geese on farm

The unique structure of the down plumes gives them their insulation properties. Down plumes are different from feathers in that they don’t have a hard central quill or spine. Each plum consists of tiny fibers that radiate out from a central point. Finer filaments branch off from each fiber. When these plums bunch together, the resulting structure traps pockets of air which trap heat that keeps you warm.

Down Fill Power

Because down is a natural product, it varies in quality. Down quality is measured in fill power. Fill power measures the down’s ability to loft or fluff up and trap heat. It is measured by calculating the number of cubic inches that one ounce of down can fill when lofted. This test is performed in a lab.

For example, if your sleeping bag uses 800 fill-power down, that means that one ounce of the down fills a volume of 800 cubic inches. 700 fill-power fills 700 cubic inches. Down fill power that is used for sleeping bags typically ranges from 600 fill to 900 fill. A higher number is better when it comes to down fill power.

Sleeping bags insulated with higher fill power down are lighter and more compressible because less down is required to fill the bag and reach a given temperature rating. This is possible because higher fill power down fills up more volume (lofts more) but weights the same as lower fill power down.

For example, a 20° sleeping bag may require 15 ounces of 900 fill power down to achieve that temperature rating. The same exact sleeping 20° sleeping bag may require 18 ounces of 800 fill power down to achieve the same temperature rating. In this example, the bag with higher quality down weighs 3 ounces less. It will compress down smaller too because there is less down inside.

down insulation
Down insulation

Historically, most down has been sourced from geese. These days, many manufactures are switching to duck down to cut costs. Goose down has become incredibly expensive in recent years.

Testing of goose and duck down is performed exactly the same so both types of down can be compared directly. Goose down is typically used in higher-end sleeping bags because it can achieve a higher fill power than duck down. Goose down reaches a maximum fill power of around 1000. Duck down maxes out at around 750-800 fill-power.

Synthetic Insulation

Synthetic insulation is typically made from polyester filaments. These are basically plastic fibers derived from petroleum and various chemicals. A number of competing companies make their own proprietary synthetic insulation with slight variations in design and composition. Synthetic insulation falls into two categories: short-staple and continuous filament.

Short-staple synthetic insulation is composed of short strands of very fine denier filaments. They usually measure less than 2 inches in length. These are densely packed together to create insulating air pockets and reduce heat loss. This synthetic material mimics the structure of down.

Short-staple synthetic sleeping bags compress well and feel soft like down. They tend to break down quicker as they are compressed and decompressed. This makes the material a bit less durable. The insulation can also more around in the shell and create cold spots.

Continuous filament synthetic insulation is made from long strands of filaments of different thicknesses. Sometimes a single long fiber is wrapped and weaved around itself. The resulting material is durable, strong, and has high-loft. It’s also a bit stiffer and doesn’t move around so cold spots are less likely to develop. The drawback is that continuous filament insulation isn’t quite as compressible as down or short-staple synthetic insulation.

synthetic sleeping bags in a tent

Down Vs Synthetic Sleeping Bag Insulation

While both types of insulation will keep you warm, they do have their strengths and weaknesses. In this section, we’ll compare the weight, cost, compressibility, efficiency, durability, and more of down vs synthetic sleeping bags to help you decide which insulation material is best for the climate you hike and camp in.


For many ultralight hikers, weight is the single most important consideration when choosing a sleeping bag. Down sleeping bags are significantly lighter than synthetic sleeping bags.

For example, an ultralight 20° sleeping bag insulated with high quality 900 fill-power down weighs around 1 lb 4 oz to 1 lb 8 oz (570-680 grams). A similar 20° synthetic sleeping weighs around 2 lbs to 2 lbs 6 oz (900-1080 grams). On average, a down sleeping bag weighs around 1 pound (450 grams) less than a comparable synthetic sleeping bag. For ultralight hikers, this one-pound is significant.

This lighter weight is possible because down lofts better than synthetics. In other words, an ounce of down fills more volume than an ounce of synthetic insulation. This allows manufacturers to use less insulation yet achieve the same warmth rating. Down offers a better warmth-to-weight ratio.

Having said this, down bags aren’t always significantly lighter than synthetic. As mentioned earlier, the weight depends on the quality of the down. A 20° sleeping bag insulated with 600 or 650 fill-power down weighs on average 2 lbs to 2 lbs 8 oz (900-1100 grams). That’s comparable to a modern high-tech synthetic sleeping bag.

Low quality down bags are heavier because they have some feathers mixed in with the down. They also tend to have thicker shell material so the feather quills can’t poke through.


Unfortunately, most of us have a limited budget for buying camping gear. If money is tight, synthetic sleeping bags are the cheaper option. A 20-30 degree synthetic sleeping bag that is light enough for backpacking usually costs somewhere between $150 and $200 depending on the features and quality.

Down sleeping bags, on the other hand, start at around $200 for lower end 650 fill models. Higher end ultralight models with 850-900 fill down cost anywhere from $300-$500. Down sleeping bags cost about twice as much as synthetic sleeping bags. If money is tight, you’re better off going with synthetic insulation.

Because down is a byproduct of the food industry, you’d think it would be an inexpensive material. This isn’t the case. In recent years, down prices have increased substantially due to the increase in demand of down jackets and sleeping bags and a reduction of supply due to changing diets. China produces 70% of down. These days, people are eating more beef and fewer geese and ducks. This drives supply goes down so prices go up. Since 2009, goose down has become 5x more expensive.

For example, 3 ounces of 850 fill goose down costs $38 at Ripstop by the Roll. To fill an average 20° down sleeping bag, you need around 16 ounces. That would cost over $200 for the insulation alone. Of course, manufactures aren’t paying this much with economies of scale. Still, down is expensive.

The one benefit of high down prices is that it motivates manufactures to work on improving their synthetic insulation technology. Hopefully, one day synthetics can achieve the incredible warmth-to-weight ratio of down.

Compressibility and Volume/Bulk

One unique property of down is that it can compress shockingly well. Much better than synthetic insulation. This unique property allows down sleeping bags to take up much less space in your pack. For example, a 20° down sleeping bag occupies around 6-10 liters depending on the quality of the down. A comparable synthetic bag might take 16-20 liters. For more info on compressed sleeping bag volume, check out this guide from Section Hiker.

There are several benefits to having a more compressible and compact sleeping bag. Most importantly, you can store your sleeping bag in a less compressed state in your pack. This way, it lofts much faster when you’re ready to go to bed. For example, a loosely compressed down bag might take just a minute or two to fully loft. The same bag might take 5-10 minutes to fully loft if it was tightly compressed. On a cold night, you can crawl in and get warm sooner.

As a bonus, your sleeping bag lasts longer when not stored overly compressed. The reason is that the insulation breaks down over time as you compress and decompress it. Eventually, it looses some of its insulation quality.

With a down sleeping bag, you can also get away with using a smaller pack. For example, many ultralight hikers use 30-40 liter packs for multi-day hikes. With a bulky synthetic bag, you’d need a 50-60 liter pack to accommodate the bigger bag. Using a smaller pack comes in handy if you often fly to your hiking destination.

down sleeping bag compressed in a stuff sack

Tip: Never store your sleeping bag in a compressed state long term. This can cause damage to the down or synthetic fibers and prevent the bag from lofting fully in the future. This is particularly important if some moisture was trapped inside. When the bag doesn’t loft properly, it won’t be as warm. After your trip, you should decompress your sleeping bag, let it dry out completely, then store it uncompressed in a large breathable bag. Most manufacturers include a storage bag when you buy your sleeping bag.

Durability and Longevity

Down is an incredibly durable and long-lasting material. The natural fibers can compress and decompress for hundreds of cycles without breaking down and losing loft. A quality down sleeping bag can last for at least 10 years without losing much warmth if properly taken care of. Some campers get 15-20 years out of a down bag.

Synthetic insulation, on the other hand, isn’t quite as durable. The fibers slowly break down each time they are stuffed and un-stuffed. This means the insulating power reduces over time. After 3-5 seasons of use, you might need to replace your synthetic sleeping bag.

It’s important to take this into consideration when pricing out different sleeping bags. You might find that an expensive down bag costs less in the long run because you have to replace it less often. For example, if a down sleeping bag costs $400 but lasts 10 years, you’re paying $40 per year to use it. If a similar synthetic sleeping bag costs $250 but only lasts 5 years, you’re paying $50 per year to use it. In this example, you’re saving $100 in the long run by buying a more expensive bag in the first place. You’ll probably enjoy using it more too.


Both down and synthetic sleeping bags can be warm enough for any trip. Most mid-range and higher models undergo the same standardized lab testing for warmth. They are lab tested by either the EN or ISO standard to find a comfort and lower limit temperature rating.

These ratings allow you to make apples-to-apples comparisons between sleeping bags with different types of insulation and from different manufactures. For more info, check out this great guide on EN/ISO testing from Therm-a-rest.

For expedition camping or hiking in extremely cold weather, down is preferable simply because it is less bulky. Most sleeping bags that are made for extreme temperatures of -20 to -60° F use down. Synthetic versions are available but they are large and heavy.

hiking in deep snow in the mountains
While camping in extreme conditions, you need to be certain that your sleeping bag will keep you warm.

Over time both down and synthetic sleeping bags lose a bit of warmth. There are two causes of this. First, the fibers can break down after being compressed and decompressed many times. When this happens, the insulation doesn’t loft as well so they can’t trap as much heat to keep you warm. How fast this happens depends on a number of factors including how much you use the bag and how tightly you compress it.

Sleeping bags also tend to lose warmth when they get dirty. For example, body oils, dirt, smoke, and other contaminants can weigh down your sleeping bag and cause the insulation to clump up and not loft properly. If this happens, the solution is to wash your sleeping bag. This usually restores the loft if done properly. More on that later.

measuring sleeping bag loft with a ruler
One way to measure loft is to simply measure the thickness of your sleeping bag after it is fully fluffed up

Efficiency and the Warmth-to-Weight Ratio

A great way to compare two different sleeping bags is to look at the warmth-to-weight ratio. This measurement is helpful in comparing the efficiency of sleepiness bags with different types of insulation but the same temperature rating. After all, you don’t just want a warm sleeping bag. You want a sleeping bag that is warm and lightweight at the same time.

To calculate the warmth-to-weight ratio, you’ll need to know the weight of the bag and its temperature rating. For example, if you’re comparing a 20° down sleeping bag that weighs 25 oz to a 20° synthetic sleeping bag that weighs 30 oz you’ll find that the down sleeping bag has a better warmth-to-weight ratio because it weighs less but has the same warmth rating. This indicates greater efficiency. Generally, down sleeping bags have a better warmth-to-weight ratio than synthetic.

This is possible because a given weight of down insulation lofts more (takes up more volume) than the same weight of synthetic insulation. This allows manufacturers to use less insulation weight to achieve the same warmth rating. This makes a more efficient sleeping bag.

Performance in Wet Conditions

Synthetic sleeping bags and jackets perform far better than down in wet conditions. The reason is that synthetic materials are designed to maintain their loft when they get wet. Even when they’re soaked, synthetic sleeping bags still provide some insulation. You won’t stay as warm as if the bag was dry but at least you’ll survive.

Another benefit to synthetic insulation is that it dries faster than down if it gets wet. If you fall into a river and your synthetic sleeping bag gets soaked, there is a chance that it will dry by bedtime if it’s sunny out. Even if it doesn’t dry, it will still provide some warmth. For this reason, you could also argue that synthetic sleeping bags are safer.

Synthetic sleeping bags are a great choice for camping in rainy or snowy environments. They are also ideal for trips where you’ll spend a lot of time on the water where there is a good chance that your sleeping bag will get wet. For example, maybe you’re kayak camping or sleeping on a boat.

hiking in rainy weather
While hiking in the rain, you need to be extra careful to keep your sleeping bag dry

Water is down’s Achilles heel. When down gets wet, it loses nearly all of its insulation qualities. This happens because moisture causes the down plumes to clump together, which pretty much eliminates any loft.

Water weight can also compress the down to further reduce loft. When this happens, there are fewer air pockets between the down particles. The sleeping bag can no longer trap enough heat to keep you warm.

Rain isn’t your only worry when it comes to getting your sleeping bag wet. Even excessive humidity can reduce the loft of your down sleeping bag and make it sleep colder. For example, according to this article from Kelty, a 15° sleeping bag can lose 30% of its loft in 80% humidity over 8 hours. Condensation inside of your tent can reduce the loft as well.

Another problem with down is that it takes longer to dry than synthetics. If your down sleeping bag gets wet, you may not be able to dry it out until you get home. It may take several hours laying in the sun for it to dry out.

For these reasons, you should avoid down sleeping bags when camping in wet or humid areas like the tropics. Those who spend time on the water like kayakers and packrafters may want to avoid down as well.

DWR Down Treatment

Technological advances over the past few years have greatly improved down’s performance in wet conditions. Modern chemical treatments create a hydrophobic coating on the down. The coating bonds to the down filaments at a microscopic level and repels water. This way, the down retains some of its loft when exposed to moisture. The treatment is also designed to help down dry faster and loft better.

A number of different proprietary treatments exist. Down treatments are often called ‘dry down.’ They are also known as DWR or durable water repellent treatments.

In my experience, DWR treated down sleeping bags perform pretty well in wet conditions. I hiked the Wonderland Tail through a 6-day rainstorm with my Kelty Cosmic 20 sleeping bag. It stayed warm and dry until the last day when some cold spots began developing due to wet clumping down.

Kelty down sleeping bag

It’s important to note that these treatments do not make the down waterproof. If the bag gets submerged in water or exposed to heavy rain, the down will still get wet and lose loft. The DWR treatment is just designed to make the bag perform a bit better in environments where it may be exposed to light moisture, humidity, or condensation. Synthetic bags still outperform treated down bags in wet conditions.

Another consideration is that some studies show that dry down doesn’t loft quite as much as non treated down. This means the bag needs a bit more down to achieve the desired temperature rating. The treatment itself also adds some weight but it’s pretty negligible.

Tip: Regardless of what type of insulation your sleeping bag uses, keeping the bag dry is crucial. The best way to ensure your bag stays dry is to pack it in a waterproof sack. I like the Sea to Summit Event Compression Dry Sack (#ad). It both compresses the bag so it takes up less space and keeps it dry. If you’re on a tight budget, you can also simply store your sleeping bag in a waterproof trash compactor bag.

Ethical Concerns

Down is a byproduct of the food industry. The same ducks and geese that we eat also produce the down in our sleeping bags and jackets. The problem is that down isn’t always ethically sourced. In some cases, the animals are badly mistreated or even abused. Factory farming can be ugly.

Unethical down is harvested while the bird is alive. The benefit to this is that down can be harvested from the same bird multiple times because the down grows back. This brings down costs. The problem is that live harvesting causes the bird great pain. The skin can tear while the feathers are plucked. In some cases, down has been linked to the force-feeding of geese which are used to produce foie gras. Sometimes, the birds are simply raised in unsanitary or cramped conditions and not allowed to roam.

Ethical down is harvested at the same time that the animal is being slaughtered. This is much more humane because the bird doesn’t have to endure much pain. Additionally, the birds must be given the five freedoms including freedom in order for the down to be considered ethical. These include the freedoms from hunger or thirst, discomfort, pain and diseases, fear and distress, and the freedom to behave normally.


To avoid supporting this industrial mistreatment of animals, you should check to make sure that the down was harvested ethically before buying a sleeping bag or jacket. Several organizations exist which certify down to prove that it is ethically sourced.

The Responsible Down Standard (RDS) was established to ensure that the geese and ducks that produce down have not been mistreated or unnecessarily harmed. This independent and global organization performs on-site audits to ensure that the animals are being treated ethically. They inspect the entire supply chain including the farm, slaughterhouse, and factories where sleeping bags are made. To ensure that the same down makes it all the way from the farm to the product, they use a transaction certificate to track the down.

Most quality outdoor gear manufactures use only ethically sourced down these days. You can look for the RDS logo on your sleeping bag or search the RDS website here to find ethical down. If you’re unsure whether or not the down in a particular product is ethically sourced, you can look up the model number on the RDS website as well.

A few more organizations that certify down include Global Traceable Down Standard, American Down and Feather Council, and Dawnmark. You may see one of their logos instead. For more info on ethical down, check out this great guide from

Of course, if you’re opposed to using animal products in general, you’ll want to stay away from down insulation entirely, regardless of whether or not it was raised ethically. The alternative is synthetic insulation, which is made from polyester. This material is made in a factory from petroleum products like oil and coal as well as various other chemicals. It’s basically a plastic. There are no ethical concerns with synthetic insulation.


Down sleeping bags cause an allergic reaction in some people. Symptoms include congestion, itchy or puffy eyes, sneezing, coughing, runny nose, etc. Basically cold-like symptoms.

In most cases, bacteria, mites, fungi, mold, etc. that live in the down cause the allergy. These organisms thrive in the down when it’s moist. In other cases, the allergic reaction is caused by dust or other particles that were not cleaned out when the down was being processed at the factory.

If you have a reaction after sleeping in a down bag, there are a few potential solutions. First, you should try thoroughly washing it with down detergent. This should kill any living organizes and remove most contaminants that could cause the allergic reaction. I’ll talk more in depth about how to properly wash down later on in this guide. You’ll also want to keep the bag as dry as possible. Never put your sleeping bag away when wet. Organisms can’t grow without water.

If you’re still having issues, another potential solution is to use a sleeping bag with at least 800 fill power down. This way, you’re getting higher quality down that has been cleaned and treated better during processing.

You can also look at the oxygen number and turbidity numbers. These measure the cleanliness of the down.

  • The oxygen number measures for organic material. Lower numbers are better. Anything below 4.8 is considered hypoallergenic. The cleanest bags measure 1.6.
  • The turbidity number measures dust and non-organic materials in the down. A higher turbidity number is better. 1000 is the maximum turbidity.

In rare cases, you may be allergic to the down itself. If this is the case, you’ll need to switch to a synthetic sleeping bag. Synthetic sleeping bags are hypoallergenic. Because they are made from man-made fibers, bacteria, mold, mites, etc. can’t live inside as easily. Having said that, synthetic bags can collect dust during use. You should wash your synthetic sleeping bag occasionally to remove any contaminants.


Another drawback to down is that it can be smelly. In some cases, it’s just a bit musty. In other cases, it downright stinks like a barnyard. There are several causes for this odor. Most commonly, there is something living in the down such as mites, bacteria, mold, etc. The odor could also come from dust or oils from the ducks or geese.

Synthetic bags, on the other had, have no odor when they are clean.

The best solution to a stinky down sleeping bag is to air it out. Find a place outside where you can hang the bag for 2-3 weeks in the wind and sun. The odor will usually dissipate over time.

Some down bags only smell when they get damp. This is particularly noticeable in humid conditions. You’ll pretty much have to live with this until it dissipates naturally. You should also make sure the bag is dry before storing it long term so mold doesn’t grow and make the smell worse.

Both synthetic and down bags obviously begin to smell once they are used heavily and become soiled. Occasionally, you’ll want to wash your sleeping bag to get rid of any oils from your skin, sweat, and dirt that have built up over time.

Environmental Friendliness

Down insulation is more environmentally friendly than synthetic because it is biodegradable. Once it is disposed of, the down breaks down and turns back into earth. After all, down is a completely natural and organic material that comes from birds.

The production of down doesn’t have much of an environmental impact either because the birds are already being raised for food. Down is a very useful and valuable byproduct of the poultry industry.

Additionally, some companies recycle or repurpose old down. They buy old down from mattresses, pillows, bedding, etc. then clean it and mix it with some new down. This new mixture is great insulation for sleeping bags and jackets. The outdoor company Patagonia uses recycled down in some of their products.

It’s important to keep the planet healthy so we can all continue to enjoy exploring in

Synthetic insulation, on the other hand isn’t quite as environmentally friendly. It is made of plastic. Once it makes its way into a landfill at the end of its useful life, it will sit for decades or centuries before it degrades. It can also break down into microplastics which can cause some serious problems for the environment.

A few companies are working on biodegradable types of synthetic insulation. For example, PrimaLoft synthetic insulation is supposed to degrade within a year. For more info, check out this interesting article. In some cases, synthetic insulation can be recycled as well.

Another problem with synthetic insulation is that the production process isn’t very eco-friendly. Several harmful chemicals and carcinogens are used in the production of synthetic materials like polyester. These can make their way into the air and water and cause ecological damage.

Sleeping Bag Construction and Cold Spots

Cold spots are a common problem on older and lower-end sleeping bags. They are created by an absence of insulation in part of the bag. For example, maybe the down clumps or shifts toward the foot of the bag so one section doesn’t have any. You’ll get cold in that particular section because there is nothing there to trap heat other than a thin layer of fabric. Some styles of stitching can also create cold spots. On a seem, the insulation is very thin so heat can escape. This is called sewn-through construction. Luckily, modern designs have basically solved the problem of cold spots in both down and synthetic sleeping bags.

Down bags use a construction technique called baffles to prevent cold spots. Baffles are walls of fabric or mesh that divide the interior of the sleeping bag into sections. They are sewn to the liner on one side and to the shell on the other.

Baffles help to prevent cold spots in two ways:

  1. Baffles hold the down in small chambers so it is distributed evenly across the entire bag. They also prevent the down from shifting around. Without baffles, the down could migrate to one end of the sleeping bag when you pick it up.
  2. Baffles eliminate seems between the liner and shell. Instead of the liner and shell being sewn together directly, they are held together by baffles. This way, the bag stays much warmer because there are no thin spots where heat can escape.

A number of different baffle techniques exist including box baffles, side block baffles, continuous baffles, stretch baffles, and vertical baffles. A sleeping bag may use multiple baffling techniques to maximize warmth and comfort.

Synthetic sleeping bag insulation is often made in sheets. These sheets are sewn directly onto the fabric of the liner and shell. The insulation sheets overlap like roofing shingles. This way, there are no gaps or seems without any insulation.

For more info, check out this great guide to sleeping bag construction from Trailspace.

a sleeping bag in a tent

Pros and Cons of Down Insulation


  • Lighter- Because down lofts better than synthetics, the bag requires less insulation.
  • More compressible- Down sleeping bags occupy 6-10 liters of space in your pack.
  • Durable and long-lasting- A down sleeping bag can last over 10 years if properly taken care of.
  • More efficient– Down sleeping bags have a higher warmth-to-weight ratio.
  • Environmentally friendly- Down is an organic product that quickly and naturally breaks down when it is disposed of. It can also be recycled in some cases.


  • More expensive- An nice down sleeping bag costs $300-$500.
  • Poor performance in wet conditions- Down loses its insulation quality when wet. It also takes a long time to dry out.
  • Can be unethical- Down is an animal product. Sometimes birds are mistreated or harmed during production.
  • Some people are allergic- Down can contain dust, bacteria, mites, and mold. These can cause an allergic reaction.
  • Down can be smelly- Natural fats and oils from geese and ducks can cause an unpleasant odor.
  • Cold spots can form- Sometimes down can shift and create spots without any insulation.

Pros and Cons of Synthetic Insulation


  • Cheaper- A synthetic sleeping bag suitable for backpacking costs $100-$200 on average.
  • Good performance in wet conditions- Synthetic sleeping bags loft and provide insulation when wet. They also dry out faster.
  • More ethical- Synthetic insulation is made in a factory. No animals are involved in production.
  • Hypoallergenic- There is less dust and organic matter that could cause a reaction.
  • No odor- Synthetic insulation has no smell.
  • No cold spots- Synthetic insulation is usually made in sheets. It can’t shift around and create cold spots


  • Heavier- Synthetic sleeping bags need more insulation. On average they weigh around 1 lb more than down.
  • Less compressible- Synthetic sleeping bags occupy 16-20 liters in your pack.
  • Synthetic sleeping bags don’t last as long- The insulation begins to break down after 3-5 years of use.
  • Less efficient- Synthetic sleeping bags have a lower warmth-to-weight ratio.
  • Not environmentally friendly- Synthetic insulation is made from plastic. Production involves petroleum and harmful chemicals.

Goose Vs Duck Down

While shopping for a sleeping bag, you may notice that there are two types of down insulation available: goose and duck. Both types of down perform equally well in terms of warmth and durability. For example, a 700 fill power duck down sleeping bag will be just as warm as a 700 fill power goose down sleeping bag. Both types of down have the same structure and insulate in the same way. Both will last for over a decade if properly taken care of.

A down producing duck

Having said this, there are a two slight differences between goose and duck down that you may want to take into consideration when buying your next sleeping bag.

  1. Price- Duck down is cheaper. The main reason for this is that more ducks are raised than geese. The demand for duck is higher because the meat is more widely eaten. Goose is much less popular. Because there are more ducks, there is a bigger supply of duck down. This brings prices down considerably. For this reason, many outdoors manufacturers have been switching from goose to duck down over the past few years. Goose down has become way too expensive. Over the past 10 years, it has increased in price 5x.
  2. Maximum fill power- Goose down has a higher maximum fill power than duck down. You can buy goose down up to 1000 fill. Duck down maxes out around 750-800. Improved sorting technology is making 850 fill duck down more common. The fill power has to do with the size and age of the bird. Older and larger birds grow larger down plumes and more of them. Because geese are larger than ducks, they tend to grow higher-quality down. Geese are also a couple of weeks older than ducks at harvest so their down has a bit more time to mature.

One more potential difference between goose and duck down is the odor. Generally, duck down smells a bit more pungent. There are several potential explanations for this. The smell may have to do with the diet of the bird. Another possibility is that ducks tend to collect more odor on their down because their chest rubs against the ground more because they are shorter. The fat and oil content in the down, also plays a role. Generally, DWR treated down smells less. Down odor usually goes away over time. If your nose is particularly sensitive, you may prefer goose down.

When it comes to durability, both goose and duck down perform about the same. Durability of down depends mostly on the oil and fat content. The more the better. Oil and fat make the down more durable by making it water resistant and pliable. It can compress more without breaking down and losing loft.

Some birds have more oil and fat content in their down than others. This could be related to their diet, the season, genetics, the weather, the way the birds were treated, the bird’s health, etc. All of these factors can also play a role in the general quality of the down. Higher quality down may be more durable.

The way the down was treated during processing also plays a big role in its durability. If too much fat and oil was washed away during during processing, the durability of the down suffers. This is the same reason that you don’t want to wash your down sleeping bag too often or with the wrong detergents.

If there isn’t enough fat and oil content in the down because of the quality of the bird or over washing during processing, the down becomes brittle. At this point, it can break down and lose loft, making the bag less warm.

For more info, check out my complete guide to duck vs goose down.

Types of Synthetic Insulation

Most major sleeping bag manufactures have their own proprietary type of synthetic insulation. They constantly experiment with new synthetic materials and designs. Every year, new and more advanced versions are introduced. The end goal is to match or beat down’s loft, weight, compressibility, and durability.

Synthetic insulation can be manipulated in a multitude of ways to optimize the sleeping bag performance. For example, manufactures can change the chemical composition of the fibers to give them different characteristics. They can change the length and diameter of the fibers. They can use fibers with a hollow center to trap more heat and vary the shape and size of the hollow center. Manufactures can also crimp the fibers to improve loft. Various treatments can be sprayed on the fibers to improve loft and durability as well. The insulation can be bonded into sheets or left loose like down.

Manufacturers constantly experiment in an attempt to improve the performance of their synthetic insulation. Hopefully, synthetic insulation technology will improve to a point where we won’t have to rely on birds anymore.

A few high tech types of synthetic insulation include:

  • PlumaFill from Patagonia
  • PrimaLoft
  • Omni Heat from Colombia Sportswear
  • Coreloft from Arc’teryx
  • Thermal R from Marmot
  • Thinsulate
  • And more

A Third Insulation Option: Down/Synthetic Hybrid

These days, some companies offer hybrid down and synthetic sleeping bags and jackets. These bags are filled partially with down and partially with synthetic insulation. In some cases, the insulations are blended together. Sometimes different parts of the sleeping bag are filled with different insulation types. For example, often the foot will be synthetic and the area around the head will be down. Different models use different ratios of each.

These sleeping bags and jackets offer the best and worst of both worlds. For example, they are lighter and more compressible than synthetic alone but heavier and bulkier than down alone. They are more water-resistant than pure down but less water resistant than pure synthetic. Price wise, they fit somewhere in between as well. Down/synthetic blended bags aren’t all that common but it is another option to consider.

A Note About Washing your Sleeping Bag or Jacket

Regardless of which type of insulation you choose, you’ll have to clean your sleeping bag once in a while. This achieves two things. First, it removes dirt, oils, smoke, sweat, or whatever contaminants your sleeping bag may have been collected. Your sleeping bag will feel and smell fresh and clean after a good wash.

Second, washing your sleeping bag restores loft. The contaminants in your sleeping bag make their way into the insulation and weigh it down and cause it to clump. By removing the contaminants, the insulation lofts better and keeps you warmer. If you feel that your sleeping bag isn’t keeping you as warm as it used to, try giving it a good wash.

washing machines
Ideally, you should wash your down or synthetic sleeping bag in a front load washing machine

How frequently you need to wash your sleeping bag depends on how much you use it and where you’ve been using it. For the average camper, once per year is fine. If you use your sleeping bag heavily, you may need to wash it more often.

You don’t want to wash your sleeping bag too often or too harshly. The reason is that sleeping bags can only be washed so many times before the insulation begins to break down and lose loft. Synthetic fibers break down as they are agitated, bent, and compressed during the washing process. Down contains natural oils and fats from the bird. These can wash off over time. When the oils are removed, the down particles become brittle and break down, reducing loft.

For these reasons, you should wash your sleeping bag gently and as infrequently as possible. You should also use the proper soap for the insulation that you’re sleeping bag uses. I recommend Nikwax Down Cleaning and Waterproofing (#ad) for washing down. When possible, spot clean your sleeping bag instead of washing the whole thing.

For more info, check out this great guide to washing sleeping bags from REI.

A Few Sleeping Bag Recommendations

Marmot Trestles Elite Eco 20 Sleeping Bag

This high quality and affordable synthetic sleeping bag is an excellent choice for those who want to avoid using down. The regular model weighs just 2 lbs. 6 oz. and offers a comfort EN rating of 32.2°F. The Trestles offers is made from recycled insulation that blends 3 different fibers for extra loft. The bag packs down into a stuff sack that measures 9.5″ x 19″.

Kelty Cosmic 20

This is one of the most affordable down sleeping bags available that is still light and compact enough for backpacking. The Kelty Cosmic 20 uses 18.2 oz 600 fill power DriDown for insulation. It is surprisingly water-resistant. The whole bag weighs in at around 3lbs. Check out my full review here.

REI Co-op Magma 15 Sleeping Bag

This ultralight down sleeping bag from REI weighs just 1 lb. 12.2 oz. and compresses down to an incredibly small 5.2 liters an included stuff sack. It is insulated with 850 fill-power goose down. My friend owns this sleeping bag and really loves it. I inspected his and was shocked by how lightweight and compact it was.

Nemo Forte Ultralight Synthetic Sleeping Bag

This synthetic sleeping bag uses PrimaLoft RISE insulation that is made form 80% recycled material. This insulation is equivalent to 650 fill down in terms of warmth and compressibility. The regular length version weighs in at 2 lbs. 14 oz. and compresses down to 12 liters. It offers an ISO comfort rating of 32 degrees F.

Final Thoughts About Down Vs Synthetic Sleeping Bag and Jacket Insulation

This decision really comes down to budget and the conditions you plan to use the sleeping bag in. If you’re on a tight budget or you plan to camp in wet conditions often, synthetic sleeping bags are the best choice. The drawback is that you’ll have to put up with carrying a bit of extra weight and bulk.

For ultralight hikers, campers, or bikepackers, down is the better insulation. It’s lighter, more efficient, and more compressible. Modern chemical treatments make down water resistant enough for most trips. The durability and longevity of down is a nice bonus as well. If the price of a down sleeping bag is a bit too high, remember that you’ll likely get a decade of use out of it.

So far, mother nature has created a lighter, more durable, and more compressible insulation than we can create in a lab with current technology. I imagine in the future synthetic insulation will catch up to the performance of down. Until then, down is the best insulation we have for sleeping bags, quilts, and jackets.

Where do you stand on the down vs synthetic sleeping bag and jacket debate? Share your experience and tips in the comments below!

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