You know you need warm layers when the temperature drops. But not just any jacket will do. Choosing the right insulation for the conditions is the key to enjoying cold-weather adventures—and staying safe.

　　Number one, you want a good warmth-to-weight ratio, and that means apparel made with either natural goose down or synthetic polyester fill. Both types of insulation are packable and warm, because they trap air and create a lightweight, heat-retaining buffer between your body and the outside elements. But beyond that, they have different properties and benefits, so choosing the right insulation for your needs depends largely on conditions and personal preferences. Do you want something that’s more water-resistant or more compressible? How do you prioritize sustainability, durability, and affordability? Here’s how to understand the differences and make the best choice.

　　Down insulation, which uses the plumage found underneath the exterior feathers on ducks and geese, offers an excellent warmth-to-weight ratio. It’s breathable, packs well, and can last for decades if it’s cared for properly. Trade-offs? Down does not perform well in wet conditions, as the feathers tend to clump in bunches, losing the loft that keeps you warm, and it’s hard to dry. Some down is treated with a water-resistant coating, but it’s still not ideal for wet weather. Also, you’ll want to check that any down used is harvested in a humane way.

　　Synthetic insulation has always been a top choice for anyone expecting wet conditions, because it still insulates when wet. There used to be a wider gap in packability, but more and more adventurers are turning to synthetic insulation for their warmest layers because innovative companies like Thermore are making huge strides in creating synthetic fibers that are sustainable, durable, and high-performing in the field.

　　Not only does synthetic insulation maintain its ability to keep you warm even if it gets wet, but it also dries quickly, making it a superior choice in harsh conditions. Synthetic insulation is also typically less expensive than goose down.

　　The Italian brand Thermore was founded on this very principle and has continued to be a pioneer in sustainable, high-performance synthetic fill. The brand was established in 1972 by Lucio Siniscalchi, who saw the rise of winter sports like skiing and knew the discipline would demand more technical apparel than what was available at the time. Thermore has been pushing the envelope ever since, developing the first recycled synthetic fill in the early 1980s. Siniscalchi saw how used bottles were being melted to create solid plastics and recognized an opportunity. He decided to have those same bottles melted to create fibers that could be used to insulate jackets. Currently, 98 percent of Thermore’s products are made from recycled content.

　　“Providing sustainable insulation and down alternatives is part of our mission and something I’ve grown up with,” says Patrizio Siniscalchi, managing director of Thermore and son of Lucio Siniscalchi. “My father pioneered the use of synthetic fibers for apparel because those fibers provide more flexibility and higher durability, and we’re still working to ensure our entire portfolio is as sustainable as possible. We aim to blend performance and sustainability with everything we do.”

　　Consider Thermore’s recent launch of ECODOWN, a 100 percent recycled insulation that has proven to be more durable than traditional down, making it a win-win for anyone who wants a jacket that’s both sustainable and performs beautifully in the field. Stio’s Skycrest jacket uses 60 grams of Thermore’s ECODOWN, for a lightweight “shacket” that’s perfect as a shoulder-season outer layer or a midlayer in colder temps. Karbon’s K3552 Epic is an even warmer option, ideal for winter sports, with 120 grams of ECODOWN in a hooded jacket with a snow skirt.

　　And that’s just one of Thermore’s innovations. The company also developed EVOdown, a hybrid tech that blends the high loft of blow-in insulation with the ease of use of rolled insulation, which is great news for consumers because it provides similar benefits of down but is more cost-effective to manufacture. Result: high-performance, more affordable garments.

　　Invisiloft is another new product that promises to revolutionize insulation for hard-charging, adventure-minded consumers thanks to its high warmth-to-thickness ratio. The new, condensed fiber is incredibly thin without sacrificing insulating properties, which will allow manufacturers to minimize bulk when making technical garments. Ultimately, with Invisiloft, brands can make a thinner jacket or sleeping bag that is just as warm as a thick puffy, in a package that’s easy to pack and wash. And yes, this new fiber is also made from 100% recycled poly that comes from used water bottles.

　　“Our RD team continuously travels to experience the latest trends and technologies,” Siniscalchi says. “It’s a process that does not stop and is constantly evolving. The goal is to provide a real benefit to the consumer, not just a cool marketing story.”

　　Translation: No greenwashing here. Since there are no federal laws regulating sustainability claims, some companies use terms like “eco-friendly” and “natural” to prey on well-intentioned consumers, making vague and misleading claims. It’s false advertising, and until the government steps in, it’s going to continue. The most common form of greenwashing is lies of omission—like claiming to use recycled content but not stating how much. Thermore provides all the details you need to understand how sustainable practices are incorporated into its products.

　　“It is our moral duty as suppliers to not just ensure that our products are meeting elevated sustainability standards but also to educate consumers on what to look for in the marketplace,” says Siniscalchi. “That’s why we are investing in initiatives to both obtain gold-standard environmental certifications and use language that is honest and clear in all of our marketing materials.”

　　“We love our job and are completely focused on both the brands that work with us and the end consumer,” Siniscalchi adds. “We want end users to better enjoy their everyday life or sporting activities to the highest level—sustainably.”

　　Based in Milan, Italy, Thermore specializes in the research, development, production, and marketing of high-quality thermal insulation for performance apparel. Through its global sales network and its production facilities in the Far East and Europe, Thermore caters to the best brands in the outerwear industry. Thermore was the first company to launch a recycled insulation and is now highly focused on sustainable innovation, using post-consumer waste such as PET bottles.