What jacket is the best for the winter?

What winter jacket has the highest warmth-to-bulk ratio?

• In particular, what is the thinnest jacket that is still warm enough for a Boston winter? I recently discovered that jacket warmth and bulk are not as tightly correlated as I once thought.

• Answer:

  Warmth-to-bulk is a difficult metric, given that conditions vary. There are a number of factors: 1) temperature - the colder it is, the colder it is. To stay warm, you need insulation that will keep your body heat from seeping out past your jacket and heating the environment. Seeping out occurs when your body transfers its heat (kinetic energy) to something that is not your body (the air, your jacket, whatever). The best insulation creates a dead space between you and the environment, which is why down is so awesome. Unfortunately, down is only awesome when it's bulky - when you compress it, all that dead space goes away and the heat leaves more quickly. Other good insulators include heavyweight fleece, multiple layers, a vacuum, and double-paned glass. 2) wind - the windier it is, the colder it feels. Since I live in Boston too, I definitely appreciate the value of having windproof technology - especially on those days (like today) when the wind chill drops the subjective temperature by 10 degrees. The most windproof thing you can get is some sort of impermeable layer, like a rubber sheet, but those tend to be uncomfortable. Goretex (there are multiple different levels of Goretex, so do your homework) or something equivalent (Schoeller Dryskin, eVent, etc) provides a "waterproof, breathable" shell that repels both wind and rain. There are also Windstopper fleeces, which basically have a less porous layer bonded to a thicker polypropylene fleece layer. They're good but insufficient on a day like today. And there are soft-shell technologies, which are a hybrid between fleece and hard shells - they're one piece jackets that look kind of like really heavyweight fleece, except they stop a substantial amount of wind and rain. They're great for most conditions, particularly if you're being active. But if you're waiting for the T for an hour, you'll probably get cold. 3) rain - the wetter you get, the colder you will be, since water conducts heat better than air. Cotton loses all of its insulating power when wet; polypro (fleece) still insulates when wet but if you're wet you'll feel miserable (and catch pneumonia and die, if you believe my grandmother). Again, waterproof breathable fabrics are great for this - although you can also use coated canvas or oilskin, if you really want to look like a New Englander, and you can use yellow rubber if you want to look like a lobsterman. And again, there are different levels of waterproof - many (like North Face's HyVent) have what's called a DWR (durable water repellent) finish, which is a chemical layer that's sprayed on to the fabric and eventually wears off. Other fabrics are intrinsically hydrophobic, so repel water until you poke holes in the fabric itself. 4) coverage - a coat only warms the parts of you that it covers. There are lots of long coats available, and if you're generally a cold person you might want to consider one of those. Also, wear a hat. So to answer your specific question, I basically recommend layering. Unlike Darby, I don't really get to choose my work attire based on warmth, so I start layering above my shirt - thick fleece, good shell, hat, gloves. Lots of people wear softshells (they're definitely less bulky), which I've never tried but which looks like it's too cold judging from the amount of blowing into hands and shivering that i see. Most of my female friends who are done pretending that how they look is more important than how they feel have long (at least knee-length) coats and spend a lot of time laughing at the twenty-year olds whom they see waiting for the T wearing skirts that don't cover their rears.