Down vs. synthetic for insulation has been the debate around many campfires. Quite a few arguments are going around, so let’s dive into the mystery and break it down to performance and other considerations for you to mull over this fall, winter, spring. If the argument hasn’t crossed your mind, let this guide pose the essential questions and bring you to a conclusion.
Down is made from the soft plumage beneath the feathers of waterfowl. What an endorsement! Waterfowl swim all winter in frigid, icy waters, the exterior feathers provide a waterproof barrier, and the down underlayer provides the insulation. Historically goose down has been the material of choice; however, supply chain constrictions have sent manufacturers toward duck down. Both materials are superb, but if you're looking for the most generous insulation per ounce, goose edges out duck down.
Synthetic insulation is made from fine strands of polyester. Variations are numerous. Major brands will often tweak the chemical recipe and patent or copyright a name for their specific flavor giving rise to a lot of confusion. However, two significant variants exist short-staple and continuous filament. Short-staple comprises short filaments that offer the product a softer feel, more excellent compressibility, and greater loft. However, they can bunch up, leaving warm and cold zones. The continuous filament is made up of, you guessed it, longer or continuous filaments. These products feel stiffer, are less compressible, but they stay put and won’t bunch up to create cold zones and are more durable.
Fill-Power presents a technical explanation and the perfect place to start our comparison. Fill-power is a roundabout way of measuring how warm the insulation is compared to its weight. Think of it this way, a 1 pound jacket (exaggeration) with 800 fill-power will be twice as warm as a 1 pound jacket with 400 fill-power. Conversely, an 800 fill-power jacket that weighs half as much as a 400 fill-power jacket will be just as warm. Fill-power is a measurement of how many square inches of volume 1 ounce of insulation will occupy. Greater air volume translates to greater warmth.
Using fill-power as our first baseline, we can describe the difference between down and synthetic insulation. Down is unmatched when comparing warmth to weight ratio. Average duck down and low-end goose down start the scales at 500 to 600 fill-power and carry up to the premium products achieving 900+ fill-power. Synthetics start their range at 350 and top out around 500 fill-power. So the highest end synthetic is still below the lowest end down. Furthermore, higher fill power means more compressible. Down beats out synthetics when size, weight, and warmth are your primary concerns. But, there are other concerns that factor into the discussion.
Wet environments change everything. When down gets wet, all the advantages described above evaporate. The fluffy air pockets collapse, become matted, and lose loft. Synthetics may not be as warm when dry, but they maintain loft and some insulating powers when wet. Synthetics dry quickly, so they recover faster from saturation. For that rainy backpacking trip, either leave the down behind or take extra precautions to keep it dry. Similar to the feathers on a goose, protect your down inside a waterproof shell.
Allergies can make this a quick discussion. If you are allergic, like some are, to down, then your choice is quite clear. If you don’t know, try sleeping on a “feather pillow” and see how you wake up. This isn’t an issue for most people but can make for a miserable first trip if you react.
The durability and life of the materials are largely dependent on how you care for them. Both can be quite durable. Longevity is more a function of the outer fabrics than the insulating materials inside. Down, when well taken care of, will maintain it’s insulation value longer than synthetics. Synthetics can mat and lose loft over time. Both materials are susceptible to dirt and grease, so wash with appropriate procedures and detergents to keep clean and lofty.
Washability and care can be a factor for some, so consider that synthetics can be washed like any other garment. Down is slightly more delicate than the competition, yet still not difficult. Don’t be afraid to clean often; removing oils and grime from both the exterior and the insulation will keep it in good health. When storing down and synthetics, do not keep them compressed. While a compression sack is excellent to minimize volume in your pack, it can cause the insulation to collapse, bunch, and breakdown if kept confined for extended periods.
Cost is a critical component. Down is going to be more expensive, and the price goes up with fill-power. For this reason, synthetics are quite attractive for first-time buyers or occasional users.
Environmental Impact the last consideration is the environmental impact. Down is 100% organic and will breakdown quickly in the natural environment. Synthetics are made from plastics and, therefore, will not break down in the natural environment. It is estimated that 30% of the microplastics in the ocean come from the textile industry. Every time you run a load of wash, microplastics extract from the garment and wash down the drain. They are too fine to be captured by filters and eventually enter the ocean and are ingested by plants and animals. We are part of the global food chain, so we inturn are ingesting these microplastics. If this concerns you, consider your buying decision and donating to 5Gyres - https://www.5gyres.org a global organization dedicated to understanding and cleaning up our oceans.