The Down vs. Synthetic Guide

The Down vs. Synthetic Guide

Life is full of choices, and some can spark intense debate. When it comes to staying warm, outdoor enthusiasts are frequently divided into two camps: people who prefer synthetic insulation and people who prefer down. If you know anyone who spends a lot of time camping, backpacking or climbing, they’ve probably expressed their opinion on which type of insulation they like best. Of course, some people also use both, although usually for different reasons.

If you’re not sure which way to go, don’t worry. Whether you’re looking for a ski jacket or a cold weather sleeping bag, we’ll give you all the information you need to choose something that will work best for your needs. To give you an even better understanding, we’ll also break down the different kinds of down and synthetic insulations that are available.

Down Insulation

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Contrary to popular belief, down insulation is not made of feathers. Down is actually the fluffy undercoating that provides warmth for geese, ducks and other waterfowl. The structure of down provides warmth by trapping thousands of tiny air pockets. It’s also breathable, which allows unwanted moisture to escape.


  • Ounce for ounce, down is warmer than synthetic insulation. No manmade fiber matches down’s warmth-to-weight ratio.
  • Down retains its shape and loft well. With proper care, it can last for decades. Few synthetics can beat down's longevity.
  • Down is highly compressible and lightweight. Although synthetic insulation has come a long way, it still doesn't hold a candle to down's ultralight weight and amazing compressibility.


  • Unlike synthetic fibers, down loses its insulating power when it becomes wet and takes a long time to dry out, especially in a humid climates.
  • Cleaning down gear requires special care. Harsh detergents and other chemicals will break down its natural loft and luster. Only very mild detergents or down-specific cleaning products should be used. Down-insulated items should never be put in the drier.
  • Although it’s not a problem for many people, down is not hypoallergenic. Although the down may not cause an allergic reaction itself, lower quality down can harbor dust particles, debris or other non-down materials, causing a reaction in sensitive people. However, high-quality down is cleaned very well according to strict industry standards, and is less likely to cause issue. If you're prone to allergies, it's wise to invest in only high-quality down products, or go with synthetic.
  • Costs is another big factor. Down insulation can be significantly more expensive than synthetic. If you’re on a strict budget or don’t plan on using your gear often, synthetic may be a better choice.

Types of Down

  • High-Loft Goose Down is made from the finest down and provides the highest warmth-to-weight ratio of any natural or synthetic insulation. It is also the most expensive insulation material.
  • Standard Goose Down has slightly less loft, but is more reasonably priced.
  • Duck Down is less fine than standard goose down and considerably less expensive.

Down Fill Power Explained

  • Down is rated according to fill power, which is directly related to the loft quality. Fill power is represented by the number of cubic inches one ounce of down will occupy. For example, if one ounce of down takes up a volume of 650 cubic inches, it is given a 650 fill power rating.
  • The quality of the down is directly related to its fill power rating. Thus, down warmth is a function of both fill power and the amount of fill in a sleeping bag or garment.
  • High-quality down has a high fill power and is much loftier than down of a lower quality, requiring fewer ounces of down to create the same level of warmth, and therefore weighs less.
  • Most outdoor gear and apparel companies use only goose down, which has a minimum fill power of 500 to 550. Goose down fill power can go as high as 800.
  • The higher the fill power, the better the down will insulate, because there is less chance of cold spots forming (spots where the down has shifted away, leaving an uninsulated area).
  • If a label doesn't specify fill power, it is usually because the down falls in a range below 400 cubic inches or the item contains less than 75% down.

Down Grades

Down also comes in a number of different grades. For example, a 90% goose down garment will consist of 90% down and 10% feathers (small parts of feathers that were not separated from the down during the manufacturing process). The higher the percentage of down, the better the warmth-to-weight ratio will be, and the higher the cost.

The Bottom Line

Down is Mother Nature's best insulator. It provides incredible warmth with minimal weight. It’s also highly compressible and has good longevity if properly cared for. Of course, the added expense may be a deal breaker for people on a budget.

Synthetic Insulation

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Unlike a few decades ago, synthetic insulation technology has become much more sophisticated. There are now numerous types of high-performance synthetic insulations available, and several come close to down in terms of warmth-to-weight ratio. Synthetic insulation is essentially polyester threading that is molded into long single threads or short staples to mimic lofty down clusters. Thinner and lighter threads fill voids and trap warm air more effectively, while thicker strands sustain the loft and durability.


  • Unlike down, synthetic insulation is water-resistant and will still provide some warmth if it gets wet. Most synthetic fills are, at the very least, resistant to moisture, while many will actually repel water.
  • When synthetic insulation gets wet, the moisture is trapped in the air pockets between the fibers, rather than in the fibers themselves. For this reason, synthetic insulation dries much faster than down.
  • If you’re on a budget, synthetic insulation will keep you warm for less money. It’s also easier to care for. Most synthetic fill sleeping bags or garments are machine washable and dryable.
  • Most synthetics are also completely hypoallergenic and will not cause allergies, as long as you keep them clean.


  • Synthetic insulation is heavier and bulkier than down, requiring more weight and volume to keep you in the comfort zone. A 30-degree down sleeping bag will always pack down smaller and weigh less than a 30-degree synthetic bag.
  • Synthetic fibers gradually break down no matter how well you care them. You may find yourself replacing synthetic products more often compared to down products.

Common Synthetic Fill Fibers


  • Polarguard® is an insulating material made of continuous synthetic fibers. It retains its loft and insulating properties when wet. It is also non-allergenic, mildew-resistant, machine washable and drier-friendly.
  • Polarguard® 3D is made of a softer fiber that more closely resembles down.
  • Polarguard® HV is made of continuous synthetic fibers, but is 25% lighter and more compressible, making it an ideal material for use in backpacking and expedition gear.
  • Polarguard® Delta is constructed of hollow-core continuous filaments. This insulation is lighter, more durable and more thermally efficient than any other Polarguard® product. These advances are achieved by a larger diameter fiber with more hollow space inside to create a stronger, higher lofting insulation.


  • Primaloft® is an ultra-fine microfiber blend that is incredibly soft, lightweight, and water-repellent. It also has a down-like softness that adds comfort. In addition to sleeping bags and outerwear, Primaloft® is also used to make winter footwear.
  • Primaloft® One has the highest warmth-to-weight ratio of any synthetic insulation currently on the market. It’s soft, durable, high-loft and made from 100% polyester microfiber. It’s also very thermally efficient, lightweight, compressible, fast-drying and water-resistant.


  • Thinsulate® was introduced as the original "warmth without bulk" synthetic insulation. Even wet, it is still quite warm. The breathable, ultra-fine microfibers trap warm air more efficiently than larger, generic synthetic fibers. Thinsulate® comes in 40, 70, 100, and 150 gram weights. The higher the gram weight, the warmer the insulation.


  • Thermolite® insulation provides an excellent warmth-to-weight ratio, even when wet. It’s also machine washable and dryable.
  • Thermolite® Extreme is a high-tech insulation engineered to provide the most warmth per weight and durability of any Thermolite® performance fill.
  • Thermolite® Extra most closely resembles the warmth, softness and fullness of down. It provides a high loft that retains its fullness and remains resilient through many uses.
  • Thermolite® Micro is less bulky than other Thermolite® products, but provides excellent softness and warmth. It’s also the most compactible.
  • Thermolite® Plus is designed for use in extreme conditions and is the most water resistant of any Thermolite® product. It also holds up exceptionally well after multiple washings.
  • Thermolite® Active is light, breathable and ideal for high-energy activities.

Other Synthetic Materials

  • Dryloft® is a two-ply laminated shell fabric designed specifically for insulating parkas and sleeping bags. Dryloft® is twice as breathable as Gore-Tex®, but not as waterproof.
  • Hollofil® is a basic polyester insulation used in some sleeping bags and apparel.
  • Liteloft® is a polyester and olefin blend used in sleeping bags and outerwear.
  • Quallofil® high-loft polyester insulation has a soft, down-like feel. It’s used primarily in sleeping bags.
  • MicroLoft® is a polyester insulation made of fibers thinner than a human hair. The dense structure traps heat more efficiently than most basic synthetics of equal thickness. It’s also highly water resistant.
  • Thermoloft® medium-loft synthetic insulation combines solid-core polyester fibers with hollow Quallofil® fibers.

Some outerwear and sleeping bag manufacturers also have their own registered brands of synthetic insulation. A few examples are ThermaWeb® from Spyder and MarmaLoft® from Marmot.

The Final Word

Can we declare a winner in the down vs. synthetic debate? Like many things in life, one is not strictly better than the other in all circumstances. Two decades ago, down was clearly the better overall option. As technology has improved, however, synthetic has made significant headway. In order to find your best match, keep these points in mind:

  • Down works well for just about everyone, unless you frequently find yourself in extremely wet conditions or you’re on a budget. Down has the highest warmth-to-weight ratio, and is the least bulky.
  • Synthetic insulation is better in wet conditions, and is easier to clean. It’s also a good choice for casual outdoor enthusiasts who only use their gear a handful of times a year and for people who prefer to save money.

Thanks for checking out our guide! Have fun and stay warm out there.

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