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The Low Down on Insulation

Understanding down and synthetic options for will help you dial in your gear and stay warm on trail. By Sandra Saathoff

Oh, to be a bird! Yes, the ability to fly would be incredible — soaring high, taking in all the wonders our backcountry offers — but that’s not quite what I mean. Birds have another superpower: down feathers to keep them warm. A microscopic view of a high-quality down feather shows the magic. Feathers have spring and hook features that trap warm air and also help stop the feather from clumping. Since I’m not a bird and staying warm on trail is important, I’ve been on a quest to learn more about the advancements in puffy gear. 

When I say “puffy,” I bet most people think about their favorite jacket, but the options for staying warm in the backcountry go far beyond jackets. On cool mornings and evenings, a pair of insulating pants and mittens can make life in camp much more comfortable. Inside our tents, a good quilt or sleeping bag keeps us warm. And, if it’s really cold, a pair of booties can help our feet stay toasty and a balaclava can contain the heat in our heads. There are so many options for gear to keep us warm, all in both feather and synthetic versions.  

When considering what to take on your trips, it pretty much comes down to four things: weight, warmth, packability and price. However, I’m going to throw in a fifth consideration — ethics. So let’s dive into the options on the market.

A hiker sits in the snow and enjoys some sun. Their back is to a snow structure, which they've built. On top of the snow structure are various articles of clothing.
Even in extremely cold conditions, with the right gear (and maybe a clever snow structure) you can stay warm on year-round adventures. Photo by Randy Givens.


Down generally comes from geese or ducks. It’s the small, puffy feathers located beneath the larger, stronger feathers. Down keeps birds warm — they even use it in nests for their young. Industry harvests those feathers for use in myriad bedding and clothing options. But not all down is equal. 

Fill weight-to-warmth ratio: Just about any time you look at the description for a piece of down-filled clothing, you’ll find a number usually in the range of 450 to 950 — that’s the down fill number. This number tells you about the quality of the down inside — its ability to trap warm air. The way scientists get that number is by testing how much one ounce of down can be compressed inside a cylinder under defined parameters. One ounce of down that compresses to 450 cubic inches equates to 450-fill down. Down in the higher range is higher quality, able to trap more warmth for the same amount of fill, and is generally more expensive. 

But that’s not the whole story. It doesn’t tell you how much down is inside each item, thus it’s difficult to determine exactly how warm a jacket is, for example. Sleeping bags, on the other hand, do come with temperature ratings — and that’s helpful when determining what to buy. High-quality down tends to be the lightest option for warm gear, with eiderdown being the gold standard in terms of warmth, weight and packability. But a lower-quality (less expensive) item can be just as warm if it contains more down (weight). This is where a personal cost-benefit analysis comes into play. How much are you willing to spend to decrease the weight of your pack? Or are you willing to carry an extra half-pound or more for a warmer, but less expensive, option?

Down’s shortcoming is its inability to work properly if it gets wet. Feathers clump, which doesn’t allow their structure to trap warm air, and drying them is hard on trail. Ducks and geese coat their feathers with body oils to help them stay water resistant and warm. The tech world has stepped in by introducing hydrophobic down, which is a coating applied to the feathers during the manufacturing process. This coating allows feathers to continue performing in mildly damp conditions, though a full dunking will still get the feathers too wet to plump up and retain warmth.

Packability: Down items are generally recognized as the best in terms of packability. Smashing all the air out of the feather-filled item allows one to really compress it. For a trip where you’re packing up each morning and then setting up again at night, this comes in handy, allowing you to fit more stuff into your pack. 

Price: Lower-quality down will be less expensive than higher-quality down. This doesn’t mean you need to sacrifice warmth on trail, but if your budget is tight, you may choose a heavier item (lower-quality down, but more of it). Another option: Make a list of those items/brands you wish you could afford and then watch for them in secondhand stores, on used gear websites or at end-of-season sales. 

A small dog cuddles in a colorful sleeping bag.
Sleeping bags come in both synthetic and down varieties, and both have their benefits (whether they are keeping you or your canine companion warm). Photo by Vickie Wallace.

Ethics: The issue with down is that it comes from birds and some of the ways it is harvested may not sit well with you. Most of the commercial down produced each year — more than 270,000 metric tons — is a byproduct of goose and duck meat industries in Europe and Asia, according to an article written by Audubon Magazine. Some of these birds may be live-plucked or force-fed for foie gras before being slaughtered. 

In order to help consumers make ethical and informed purchasing decisions, standards have been developed that track all parts of the supply chain, from hatcheries to slaughterhouses to gear manufacturers. Looking for one of these standards may help alleviate some ethical discomfort: Global Traceable Down Standard, Responsible Down Standard, Downpass, and International Down Standard. Each standard is slightly different and, if this is important to you, you can read up on them before making purchases.


For those who would prefer to avoid purchasing down, there are many synthetic alternatives available. Like with down, the options vary in their warmth-to-weight ratio, features and price. 

Synthetics try to mimic down’s warmth ratings while improving its performance in wet weather. There are two form factors for the insulation: sheets (continuous filament) and strands (short staple). Continuous filament insulation uses a sheet that is lofty, strong and durable. The insulation stays in place, preventing cold spots. Short staple insulation is made up of strands of finer filaments that are packed together to minimize heat loss. These items require pockets or baffles in order to keep the insulation in place, while continuous filament insulation does not. Short staple insulations act and feel more like down and are more compressible, while continuous filament feels somewhat stiffer and less packable but are generally warmer. 

A hiker sits in their puffy under a tarp in the snow.
Having solid insulation allows you to slow down and enjoy the fresh air. Photo by Sarah Vaughn.

Fill weight-to-warmth ratio: Synthetic manufacturers often make it more difficult for consumers to determine the warmth rating. It’s often hidden in the product spec sheets, rather than being listed on each product or website. For synthetics, this number is called the CLO and measures the amount of clothing needed to keep someone comfortable while sitting in a room that is 70 degrees and 50% humidity. A value of zero is assigned to a naked person, while a value of 1 is a clothed person who is perfectly comfortable. Most of the brands we are familiar with have ratings for jackets in the 0.65 to 1.4 range. Sleeping bags and quilts have the same temperature rating system used with down. 

Weight: Generally speaking, synthetics will be heavier than down-filled items. However, some of the newer options in synthetics are approaching the light weight of down. For example, a quick look at insulating booties found that both the down and synthetic versions are approximately 2 ounces per pair. And one of the most popular jackets worn on the PCT is just under 8 ounces, lighter than many of the down options. 

Packability: Packability very much depends on the style of insulation, with short staple packing smaller than continuous filament. Short staple insulation offers compression similar to down-filled items.

Price: Lower-quality synthetics will be less expensive, but you can find items that perform well for middle-of-the-road prices. And, again, check thrift stores, used-gear websites or sales for bargains.

Ethics: Synthetics have their upsides in terms of animal welfare, but there’s no ethical free pass. Critics of synthetics point to the facts that the materials don’t last as long as down, are often made from polyester (petroleum industry/plastic-based) and can shed microfibers when washed. A 2019 study by the International Down and Feather Bureau looking at a lifecycle analysis of polyester vs. down fill reported that the environmental impact of down is 97 percent lower than that of polyester. 

Care & Storage

Regardless of which type of insulation you settle on, care and storage is more or less the same. Clean your items when needed, following manufacturer’s recommendations, and store them in a temperature-controlled, dry area where they can be fluffy — an indoor gear closet, for example. Dirt, oils and long-term compression are the death of your items’ ability to loft and trap heat when you most need them. 

A person sits in their sleeping bag while wearing a jacket. They are enjoying chocolate candy while looking at a beautiful view.
The right insulated gear — like a jacket and sleeping bag — can keep you warm while you enjoy a spectacular view. And Peanut M&M's don't hurt, either. Photo by Ryley Haveman.

Until humans develop the gene to grow our own down feathers, we’re always going to need to sort through clothing and sleeping gear options to stay warm when adventuring. Now that you know more about down and synthetic options, you can dive into shopping from a more educated perspective. Regardless of your choices, one of the best ways you can practice sustainability in the long term is to choose quality items that will last a very long time. 

Stay warm out there while you enjoy the view!

This article originally appeared in the Spring 2023 issue of Washington Trails Magazine. Support trails as a member of WTA to get your one-year subscription to the magazine.