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What’s the Difference Between Down and Synthetic Insulation?

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When writing our guide to the best women’s parkas, a big question I came up against was whether synthetic puffers are as warm as down ones. And while the answer is technically “no,” it turns out that a polyester parka is often still a great choice — especially for people who live in rainy climates, want to save on dry-cleaning bills, or are ethically opposed to wearing clothing stuffed with feathers.

The “humble goose” is still warmest

“Despite our efforts, humans haven’t yet been able to engineer anything better than what a humble goose can make,” says Eric Goodwin, outerwear designer and founder of Lathley. Which is why down has been used in clothing and sleeping bags since forever, with goose down being slightly warmer (and more expensive) than duck down. As my fellow writer Jeremy Rellosa explains here, the amount of volume that one ounce of down takes up, otherwise known as its fill-power rating, is crucial. The higher a down jacket’s fill power, the warmer it will be, because that one ounce of down will provide more loft and have the ability to trap more heat. “The fill power will tell you more about the quality of a jacket,” says Goodwin. “And you want to find a company that uses responsibly sourced down and doesn’t support practices like force-feeding or live plucking.”

But synthetic is catching up

Synthetic insulation is made from polyester fibers that have been engineered to mimic the warmth of down, and often its compressible puffiness too. PrimaLoft and Thinsulate are two leading technologies, but some outdoor brands have come up with their own proprietary synthetics — think The North Face’s ThermoBall or Patagonia’s Nano Puff. You’ll also see brands like Save the Duck, which manufactures synthetic jackets specifically for vegan clothing consumers. This is a constantly innovating space, and high-end synthetic-fill products are getting closer and closer to replicating the average warmth of down ones.

Down will stay puffy longer than synthetic

Weight and compressibility should also be taken into account alongside warmth. Synthetic fill is a little heavier than down, and it doesn’t compress as nicely, which is an issue for packable jackets and ultralightweight sleeping bags. Down will retain its puffiness for decades, whereas synthetic fill will flatten over time, slowly losing its insulating powers. The expensive synthetic sleeping bag I purchased ten years ago has thinned out a lot, to the extent that I can no longer use it in cold weather. My parents, meanwhile, are still comfortably sleeping in down bags that they purchased in the 1980s.

Synthetic is better in wet climates (and in washing machines)

Down loses all of its insulating powers the second it gets wet, whereas synthetics will still keep you toasty even when soaked in rain or sweat. So if you live in a rainy climate, a synthetic jacket makes a lot of sense — you might also consider a down jacket with excellent waterproofing, like the Arcteryx Pantera.

Lastly, let’s talk about washing machines. Laundering an expensive down jacket takes a fair bit of bravery and know-how, whereas polyester puffer owners have much less to fear. Is this a serious consideration? As someone with a visibly discolored Canada Goose hanging in her closet, I’d say “yes.”

Some women’s parkas we like

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What’s the Difference Between Down and Synthetic Insulation?