Coreloft is a synthetic insulation developed by Arc’teryx for their Atom range of clothing. It consists of a layer of ‘fluffy’ polyester which traps heat generated by your body.
Coreloft has several advantages over down insulation, the primary one being that it is a siliconized polyester so does not absorb water. If your Atom jacket gets wet, then it will still keep you warm. This is a massive advantage in damp environments like the UK
The second advantage over down feathers and loose fill insulation is that Coreloft comes in a sheet. This means it can be easily layered inside a jacket without the need for baffles and the meters and meters of stitching needed to stop down feathers all sinking to the bottom of your jacket. This keeps the weight down and the warmth up as wind cannot get in through stitching and there are no cold spots.
Coreloft can be packed down and unpacked almost endlessly as the crimped fibers retain their loft meaning that in the warmer months your Atom jacket can sit in your pack for emergencies.
Coreloft insulation can be found in the new Arc’teryx Atom LT jacket, as well as the heavier, warmer Atom AR and the superlight Atom SL.