Down vs. Synthetic: Which Insulation is Right for You?

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When you’re shopping for a new sleeping bag or puffy coat, one of the most important decisions you’ll have to make is between down and synthetic insulation.

The type of insulation directly affects the warmth, weight, water resistance, compressibility and price of sleeping bags and jackets. Both down and synthetic have pros and cons when it comes to performance, so choosing the right type of insulation for your use can turn a cold, uncomfortable outing into an enjoyable journey in the great outdoors.

Let’s take a closer look at down and synthetic insulation to help make your decision easier.

Sleeping Bags

Down Insulation

A common misconception is that down insulation is made from the feathers of a bird. Down is actually the plumage that’s found underneath the exterior feathers on waterfowl such as ducks and geese and consists of soft, fluffy, wispy filaments. Some products use a blend of down and feathers, but by definition, down is different than feathers.

Down insulates by trapping air and is prized for being light, easy to compress, long-lasting and breathable. It’s the insulation of choice in cold, dry conditions, or whenever reducing weight and saving space are top priorities.

Down insulation has typically been sourced from geese. However, many major manufacturers have recently made the transition to duck down throughout some or all their product lines due to the rising cost of goose down. All testing and performance standards are the same for duck down and goose down, so either way you can be assured you’re getting a high-quality product. However, you’ll find that goose down is often still used in the highest-end products because it is capable of reaching a higher fill-power rating than duck down.

Fill power is the term used to measure down’s ability to loft, and thus trap heat. It is calculated by how many cubic inches one ounce of down can fill in a testing device. For example, 600-fill-power down means that one ounce of that down fills 600 cubic inches of space. Premium goose down can reach 900 fill-power, and potentially even higher. Duck down can achieve fill-power ratings no higher than 750 or 800.

The advantage of higher-fill-power down is that sleeping bags and jackets require less down to fill space and achieve a certain temperature rating. Less down equals a lighter product. So a sleeping bag rated +20°F with 700-fill-power down will be lighter than a +20°F bag using 600-fill-power down (assuming the fabrics and other features are comparable in weight).

The most common criticism of down insulation is its tendency to clump up and lose loft when it gets wet, thereby losing its insulation properties. Within the last few years, proprietary technologies have been developed to treat down at a microscopic level with a water-resistant application. This treatment allows down to resist light moisture without compromising loft. However, if submerged in water or exposed to heavy rain, even treated down will get wet, so do your best to keep your down-filled items dry.


  • Higher warmth-to-weight ratio than synthetic insulation
  • Very compressible
  • Very durable; with proper care, a down sleeping bag or jacket can last for decades


  • Loses insulating power when it gets wet and takes a long time to dry
  • Cleaning down requires special care
  • Not hypoallergenic (rarely an issue)
  • More expensive than synthetics

Synthetic Insulation

Synthetic insulation is popular for its strong overall performance and friendly price tag. Typically made of polyester, synthetic fill is quick-drying and insulates even if wet (something down struggles to do).

It’s also less expensive than down insulation, and is durable and hypoallergenic.

There are many competing brand names for synthetic insulations, which can make shopping confusing. A more relevant distinction is knowing whether a synthetic insulator is short-staple or continuous filament.

Short-staple insulations feature short strands of fine-denier filaments that are densely packed to minimize heat loss. This makes sleeping bags and jackets feel soft and flexible, much like down-filled products, and allows for great compressibility. They are, however, a bit less durable than continuous filament and the insulation can move around to create cold spots.

Continuous-filament insulations use a thicker continuous filament that is lofty, strong and durable. They tend to have a stiffer feel and are less compressible than short-staple insulations, but they stay in place so are less likely to create cold spots.


  • Very water-resistant and continues to insulate even when wet
  • Hypoallergenic
  • Less expensive than down


  • Heavier and bulkier than down insulation
  • Offers less warmth for its weight than down
  • Less durable than down; insulating power gets reduced each time the bag is stuffed into a stuff sack

Down/Synthetic Blends

Some manufacturers make sleeping bags and jackets with a combination of water-resistant down and synthetic insulation. This hybrid construction can provide the benefits of both materials while limiting each material’s imperfections.

In some cases, the two types of insulations are blended together throughout the sleeping bag. In others, the insulation may be in different locations, for example, durable synthetic on the bottom of a sleeping bag and lofty down on top.


  • Lighter weight and more compressible than synthetic alone
  • More water-resistant than down alone
  • Less expensive than down alone


  • Heavier and bulkier than down alone
  • Less water-resistant than synthetic alone
  • More expensive than synthetic alone

So what’ll it be, down, synthetic or a combination of the two? Think about where you’ll be going, how much weight you want to carry, the weather you’re likely to encounter and how much money you’re willing to spend. But, most importantly, once you find the right sleeping bag or insulated jacket for you, get out in the mountains and have some fun.

Need more information on choose the right sleeping bag?
Sleeping Bags for Camping: How to Choose
Sleeping Bags for Backpacking: How to Choose

Editor's note:

Regarding responsible sourcing, we (REI) share your concerns and have been looking into this topic for some time. We work closely with our industry partners through the Outdoor Industry Association (OIA) to understand the issues and develop solutions that can meet our values.  To honor this commitment, we have adopted the Responsible Down Standard (RDS) for 100% of our REI private label down and feathers.  Many other leading outdoor brands have also adopted the RDS standard.

This standard ensures the down used in our product will come from ethically treated fowl.  Independent, professional certification bodies inspect each part of the down supply chain. Every time products with RDS down change ownership, a certificate (called a Transaction Certificate) is required to track the material from the source to the final product. The RDS ensures that any final product (for example, a jacket or sleeping bag) that comes with an RDS certification claim was made with RDS down.

We invite you to read more about our other practices in our Stewardship Report.

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