Down may have a warmth-to-weight ratio higher than anything more solid than steam, but it also has its problems. Down relies on its fluffy, air-capturing loft, so when it's wet, it's all but useless. Down also tends to get all bunched up in certain areas, leading to hot and cold spots.
Tactile manufacturers have long been trying (but coming up short) to improve upon down. The Zero-Loft Aerogel used in the Champion Supersuit seems to offer the most promising solution, and waterproof down also looks good.
The North Face recently added a new solution: ThermoBall. Essentially a fake down, ThermoBall consists of little balls of insulating fabric that provides for trapped air similar to feathers. The fluff balls are as light and compactable as down, and they maintain their insulating quality when wet.
It's still not quite as warm as down, but TNF does say that ThermoBall is 15 percent better warmth-to-weight ratio than existing synthetic insulation.
The first ThermoBall jacket will debut next summer for $280.
Via Popular Science