I thought this was an interesting explanation of the military PCU layering system. It would be expensive for most civilians to own all the pieces listed but it's a nice way to look at your clothing system. The same can be replicated with commercial clothing. The thing to remember that not all layers are really layers that are worn together. They are a system that you mix and match depending on conditions.
Seven levels of PCU
Wearing the PCU is a matter of mixing and matching the gray garments according to the anticipated conditions and activities of the user. Comfort levels range from -50°F to 45°F, and although there are seven levels of protection, clothing in each level is not progressively added or removed the colder or warmer the environment.
A durable, silkweight Polartec Power Dry fabric worn next to the skin wicks away moisture and dries fast. It consists of a crew neck T-shirt and boxer shorts, or is available in long-sleeve top with invisible zipper and pants, built for comfort and minimal weight.
A long-sleeve shirt and pants made from Polartec Power Dry fabric are worn next to the skin for extra warmth in extreme conditions, but still wicks away moisture quickly from skin and dries fast. An inserted side panel of Polartec X-Static fabric enhances fit and flexibility. The top has a front 15-inch zip for extra venting and a soft lining around the collar. Comfort features include an articulated side seam on the pants to minimize chafe on the kneecap.
An insulative mid-layer jacket made from Polartec Thermal Pro High Loft fabric is water-repellent yet breathable. It is worn as an outer jacket in mild temperatures or as a heavy insulative layer in extreme cold. Seamless shoulders minimize chafe, which are then lined for extra warmth and padding for heavy pack straps.
The soft windshirt is made from an encapsulated microfiber that repels water but also breathes for a variety of conditions. It is designed to pair with a next-to-skin layer for intense activity in cooler temperatures or with the Level 5 soft shell as a mid-layer. It stuffs into its own pocket for easy packing.
The key to the entire system, this soft shell fabric jacket and pants are made with fibers encapsulated with silicone that are highly stretchable, windproof, water repellant and breathable (EPIC by Nextec). They are paired with Level 1 or 2 next-to-skin layers, ready for any cold weather aerobic activity.
A lightweight waterproof and coated nylon hard shell is slightly oversized to fit easily and quickly over gear. The jacket features water-resistant zippers and armpit zips for maximum ventilation, pocket openings to quickly access inside layers and a hood that incorporates a stiff brim. The pants borrow the same design from Level 5 but provide waterproof protection.
For extreme conditions, this lightweight, loft-insulated level in a jacket, vest and pants has the feel of down but retains its warmth when wet. Silicone-encapsulated fabric sheds water and is paired with Primaloft insulation for maximum warmth while the liner pulls away moisture.