Synthetic Jacket
https://www.switchbacktravel.com/best-synthetic-insulated-jackets
1) Arc’teryx Atom LT Hoody ($259)
https://www.rei.com/product/175331/arcteryx-atom-lt-insulated-hoodie-mens?cm_mmc=aff_AL--38931--52463-_-NA&avad=52463_d259ae495
Down insulation consists of either duck or goose feathers. This is a natural insulation that is formed into clusters. Every down jacket has a fill-power rating that typically ranges from 450-900. The fill power rating is determined by measuring how many cubic inches an ounce of down creates. A simple way to put it, the higher the fill power, the warmer the jacket for the weight. Typically, common down jackets will range between 400-500. These jackets are typically lower quality. If you find a jacket that is 550 or higher, then you will be in good hands. The other factor that comes into play is the fill-weight. A lot of people tend to focus on the fill power but neglect the fill weight. The fill weight will tell you how soft or firm the jacket is and how well it compresses. Down jackets have the ability to easily be stuffed into backpacks, so a lower fill weight will make it super easy to pack versus a higher fill weight. Now that you know about fill power and fill weight, it's time to figure out how warm your jacket will actually be. Below are perfect examples by Triple F.A.T. Goose: A jacket with 500 fill power and 10 oz. of down will be warmer than a 800 fill power jacket with 5 oz. of down. With the down weight and down to feather ratio being equal, an 800 fill power jacket will be warmer than a 500 fill power jacket. An 800 fill power jacket will require less down than a 500 fill power jacket to provide the same warmth. Making sense of the fill-power to fill-weight can get confusing but you can see that a jacket that provides 800-fill doesn't necessarily mean it will be warmer unless the fill-weight is the same. This is why a majority of our top performance jackets, for example Summit Series collection, will be at a fill-power of 800 because they can keep the weight low while still offering maximum warmth. The downside to down insulation is that it loses it's warmth when it gets wet. When down gets wet it also cause the fibers to clump together creating cold spots. There is a better solution to this... Synthetic insulation
Synthetic insulation, on the other hand, is typically made of a polyester and is designed to mimic down, but retains warmth even when wet. It is also known to be quick-drying. The price of synthetic insulation also tends to be less expensive. When determining synthetics, you should know whether it is short-staple or continuous filament. Short-staple insulation uses short strands of denier filaments which makes your jacket softer, more flexible, and allows you to compress easily when you decide to pack away your jacket. The downside is that the fibers easily move around and bunch up to create cold spots within the jacket. Then you have continuous filament which is thicker, with more loft and durability. These jackets tend to be a bit stiffer and less compressible, however you don't have to worry about the fibers moving around to create cold spots.
Warmth in synthetic jackets are generally expressed in grams per square meter. They generally range from 40-200g of insulation. 50-100g of insulation are generally great for Spring/Fall weather or when you know you will be layering, while100-200g of insulation are designed for those cold temperatures that reach below freezing. Reminder: There are newer technologies of synthetic insulation where the rules don't always apply (High-Tec insulated jackets) that are built for aerobic activities to stay warm while letting your jacket breath more.
These are the basics when considering your next down or synthetic jacket and its warmth. It is important to stay safe with the proper gear when you are under extreme weather conditions. With the proper, high-quality jacket you will be warm, comfortable and enjoying every moment of your next adventure.