Books and volumes had been written on this one topic alone and I don’t have anything novel to offer. I am just going to illustrate the concept of layering from my personal experience and maybe that helps you to decide on attire on your next trip.
The concept of layering is quite simple, the problem is to find something that work. There are mainly three layers – base, insulation, and protection.
Base layer is what the name suggests, clothes that is next to your skin. The problem with wearing your typical cotton t-shirt is that cotton absorb your sweat/moisture and makes you hot in the summer, but cold in the winter. Thus the purpose for base layer is moisture wicking. In layman’s term, it is your Quick-dry t-shirt that you wear to jog or to shoot hoops. There are obviously long and short sleeve, as well as different thickness that you have to adjust base on weather. Fancier options include merino wool, Capilene and Coolmax (which are both synthetic fibers).
Insulation layer is likewise what the name suggests, a layer that retains heat. Air is a poor heat conductor and therefore the better this layer traps air, the better. Your fleece jacket or down jacket (AKA puffy jacket) will fit the bill. For down jacket, typically the higher the number (500, 600, 800, etc), the more down the jacket packs in and the better it insulates… and this insulation will be gone if your down jacket gets wet. Fleece jacket however will retain heat even when it is wet, though it is not as compressible as a down jacket.
The purpose of the protection layer is to guard against wind, rain and snow but also to let your perspiration to escape, or breathable (which otherwise would condense within and cause you to feel chilled). Also known as hard shell, there are lots of options to choose from, ranging from a nylon poncho (weather-resistant but not breathable), to a waterproof jacket, and to a windproof jacket (which might not be water-resistant). According to ultrahiker Andrew Skurka, there are currently no silver bullet in this department, and over time the water resistance will diminish as the chemical coating on your jacket fades. There are aftermarket wash that you can use to recoat, however.
With that being said, the picture below shows my most used setup. I don’t know if that’s “correct”, but this kept me warm when we were camping out in the snow. Maybe because I accidentally caught on fire, but that’s a different story…
1 – polyester long sleeve shirt, 2 – light to mid-weight fleece jacket, 3 – water-resistant (and fire proof?) hardshell
P.S. What about soft-shell?
Softshell is a type of jacket that combines the protection and insulation layer, as shown in the picture below. I haven’t felt confident enough to use it on a trip yet, though for daily errands it works well. They tend to be more expensive, so I would personally avoid them unless you find a good deal (or receive one as a gift as I did!)
- REI layering basics
- How to layer clothing for each season
- Layering guide at Sierra Trading Post