Down vs. Synthetic Sleeping Bags

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Shopping for sleeping bags can be overwhelming, especially when it comes to deciding between synthetic vs. down insulation. There are a lot of great options with both types of insulation, and when choosing a sleeping bag there are other things to consider like the shape of the bag (mummy, barrel, rectangle, or quilt), what temperature rating, and overall what’s the most comfortable for you.

To help you better understand the insulation types and make that decision easier, here’s a breakdown of down vs. synthetic insulation.

Down Insulation

Photo by Ultralight Outdoor Gear

Down is plumage found underneath the exterior feathers of waterfowl and it insulates by trapping air. It’s rated highly for being light, easy to compress, long-lasting, and breathable. It’s a great insulation for cold or dry conditions, or whenever reducing weight and saving space are a priority.

When shopping for down, you’ll see on the specs what “fill power” the down is rated. Fill power is the term used to describe the down’s ability to trap heat. This is calculated by testing how many cubic inches one ounce of down can fill in a testing tube. An example to explain this: 600 fill-power down means that one ounce of down fills 600 cubic inches of space. Higher fill-power down means the product (sleeping bag or jacket) requires less down to achieve a certain temperature rating. Put simply, less down means a smaller and more lightweight product.

Pros

  • Lightweight material
  • Very compressible 
  • Higher warmth-to-weight ratio than synthetic
  • Very durable, if taken care of properly, it can last for decades

Cons

  • Loses insulating power when it’s wet
  • Take a very long time to dry
  • Cleaning down requires exceptional care
  • More expensive than synthetic

Synthetic Insulation

Down vs. Synthetic: Synthetic material
Image from Burton

Synthetic fill is typically made of polyester and is known for being quick-drying and continuing to insulate even when wet (something down can’t do). This insulation is great if you’re not worried about weight and if saving money is a priority. When shopping for synthetic, there are a lot of competing synthetic material brands out there. Pay attention to whether the synthetic material is short-stapled or continuous filament.

Short-stapled insulations have shorter strands of fine filaments. These are densely packed to minimize heat loss. This helps sleeping bags and jackets feel soft and pliable, and it also makes the product easily compressible. They are less durable than continuous filament insulation, however. 

Continuous filament insulations are exactly what the name says: heavier continuous filaments that are lofty and durable. They will have a stiffer feel and won’t compress down very well, but they stay in place so there won’t be as many cold pockets.

Pros

  • Water-resistant and will continue to insulate even when wet
  • Hypoallergenic
  • Less expensive than down

Cons

  • Heavier and bulkier than down
  • Less warmth-to-weight ratio than down
  • Less durable than down; insulting power goes down each time the bag is stuffed into a stuff sack

Down/Synthetic Blends

Photo by Outside Online

This hybrid construction combines the benefits of each insulation while limiting the imperfections. In some cases, the blend is throughout the whole product, while in others they are split into sections (e.g. a sleeping bag having durable synthetic insulation by the feet and plush down around the body).

Pros

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

Cons

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

And that’s the breakdown of down vs. synthetic insulation. As you’re shopping, take into consideration where you’ll be going, how long you’ll use the product, how much weight you want to carry, and what your price point is. And once you’ve decided, get out in the mountains and have some fun!

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