SUL Climashield jacket
The SUL (super ultralight) series garments are aimed at pushing weight as low as possible without compromising function. The SUL Climashield is the synthetic version in the line-up. It is a warmer than fleece, lighter than fleece, breathable, fast drying, wet environment, active insulation layer with good ventilation that can be put on (backwards) without removing a backpack, won't get compressed under the pack or it's straps, and won't purge as many micro plastic fibers into the environment. It has an Argon 67 outer shell, Climashield apex insulation, and a breathable mesh inner layer.
Fill - 2.5oz/yd Climashield APEX
Total weight - 6.9oz (small)
Climashield synthetic insulation is great for wet/moist environments as it holds it's loft, doesn't absorb much, and dries fast. It's clo/oz value (insulation) is more than double the best fleeces and soft shells and it's continuous filament construction loses very few microplastic fibers. A mesh inner "shell" feels soft against the skin when moist instead of the sticky/clammy nylon shell materials. It allows for extremely fast dry time, as moisture can pass right through the mesh uninhibited. Since air can pass right through the mesh and the Climashield insulation, the only thing really inhibiting air transfer is the Argon 67 outer shell, which has been tested to have a CFM rating of almost 50. This is close to the air flow rating of windblock fleeces, but with over double the insulation value per weight in the APEX batting. The Argon shell also has a DWR finish that causes rain to bead up and run off.
Wearing with a pack -Typically, to put on your insulation, you have to remove your pack, put the item on and put the pack back on over it. Then once you do this, the insulation in the garment gets compressed under the pack and under the pack straps. These areas tend to get wet with sweat and the long term compression combined with the sweat oils pressed into the insulation degrades it heavily. The SUL snap front design adds less than 2/10ths of an ounce to the jacket and allows the garment to be put on/taken off over backpack straps, without removing the pack. The jacket is put on backwards and snapped at the top behind your neck/over the straps and snapped at the bottom by your lower back/below the pack. This leaves the pack against your back and the jacket cinched along it, but never under it. No compression and no sweat and oils pressed into it.
If I had to bring just one insulating layer for most environments, this would be it. Super light, breathable, good ventilation, holds up in wet weather, dries extremely fast, and has enough insulation in the 2.5oz/yd APEX to provide inactive warmth too.
Selecting a dark outer shell can speed up dry time even more as you can set the dark side in the sun and moisture moves right out through the mesh....fast! If even more breathability is desired, an uncalendared fabric can be used at a small weight penalty.