Sitka's Kelvin Lite Hoody. Photo credit: Brady Miller
KUIU's Original Superdown Hooded Jacket. Photo credit: Stefan Wilson
First Lite's Cirrus Ultralight Puffy Jacket. Photo credit: Stefan Wilson
First Lite's North Branch Soft Shell Jacket. Photo credit: Brady Miller
Last time I broke down considerations for base layers. You can check out that article here. After you have selected the proper base layers, then you can start building your layering system. It is absolutely essential that you understand that base layers are the most important piece of your system. Don't think that you can buy cheap base layers in order to afford a great outer shell; make sure that your base layers are solid and then begin selecting these next pieces.
The layer that will follow the base layer is your insulation layer. Insulation layers have traditionally been comprised of down jackets; however, interest in synthetic insulation has been increasing in recent years. Here is a breakdown of the two different options for your insulation layer:
Down insulation retains heat very well, which is why it has been the historical staple of insulated clothing. Yet, down is not inherently moisture resistant. Traditional down loses its thermal properties once it gets wet. New technologies in this area have made it possible for down to be coated, which makes it water-resistant/repellent. This has expanded the versatility of down, making it a great option, especially when sitting in one place for a long time when heat retention is critical. One of the drawbacks of down is that it will settle and doesn’t stay evenly distributed. This can be managed through narrow chambers in the jacket construction, but it is still a problem since the down breaks apart over time.
Synthetic insulation is preferable in some instances because it is water-resistant, breathes well, and is capable of keeping its shape (and not breaking down over time). Synthetic insulation is the preferable option when a versatile insulation layer is needed and you are after something that can retain warmth while breathing well under physical exertion. Additionally, synthetic insulation, much like synthetic base layers, dries very quickly. The only downside is that synthetic insulation does not have as good a quality of heat retention that down has (to some degree).
In order to prevent insulating materials (specifically, down feathers) from migrating through jacket layers, insulation fabrics must be coated. This coating causes warmth to stay within the garment, which, essentially, keeps the fabric from breathing. When your body is under stress (hiking in mountainous terrain) you produce more heat than normal. If your insulation layer cannot breathe, you will perspire at a higher rate. Combine this with down that doesn't dry quickly and you might want to consider synthetic if you tend to be active in very cold weather.
When choosing an insulation jacket, you will likely have a choice between a hooded or collared (non-hooded) option. If you hunt in very cold/windy conditions or if you foresee yourself wearing your insulation jacket as a stand-alone piece on occasion, a hooded option might be good for you as the hood offers additional protection and insulation for your head. Be aware that the hood can be annoying under an outer shell. It also adds weight, albeit a very small amount.
If you will be wearing the insulation layer mainly under your outer shell, a collared option might be better since it will be easier to fit under your outer shell.
Your outer shell is not the most important part of your layer system even though most people act like it is based on how much money they spend on it. While an outer shell is important, it's function is not as essential to your comfort and health as you may think. An effective outer shell possesses four qualities: wind-resistance, water-resistance, breathability, and relative silence.
An outer shell is meant to be used to fill the gap between your insulation and rain gear where rain gear is the highest level of defense against rain and wind and insulation is the highest defense against cold. An outer shell should be versatile enough to handle both jobs relatively well in mild weather while also acting as another insulation layer in the severe cold. It is important to note that an outer shell is not 100% water or wind-proof; it will do the job in mild wind and mild rain, but when it gets really nasty, the outer shell will not be able to hold up.
An outer shell is often intended to also be breathable and relatively quiet (especially when developed for bowhunters). It is impossible for something breathable and quiet to also be effective at stopping wind and rain. The types of materials needed to accomplish these respective purposes are just different.
Find an outer shell that does all of these relatively well and you will be happy. There is no holy grail in outer shells; some will excel in one area while others will excel in another. The key is finding one that fits well, is comfortable, is not too heavy, and breathes well so that you are not constantly feeling like you need to take it off during times of activity.