Thought I’d just share my experiences with RBH designs new cuben vapor barrier jacket (I am in no way affiliated with them – other than having purchased a few products from them)
I’m a big fan of a vapor barrier system and have loved their NTS jacket. This cuben model is fantastic. I’ve had it about 2 weeks now – used it for early morning runs and hikes. Lowest temp so far 29 F. It’s so light weight and feels so good against the skin you don’t even know it’s there.

I’m not sure what weight of cuben fiber this is – it's fairly delicate though. The total jacket with detachable hood weighs 4.8oz on my scales. I had them customize the venting zips a little as I often find myself engaged in high output winter activities (ultra marathons, Arrowhead etc) I highly recommend these options to anyone else thinking of a vapor barrier since they greatly increase the flexibility of the product. Basically I had them extend the pit zip all the way down the sides of the jacket and also extended the forearm vents to run almost the full length of the sleeve. This allows me to dump heat really quickly if I begin to sweat – without having to take the jacket off. With that kind of ventilation one can use this jacket in the summer as a rain jacket too. All in all a very flexible piece.

Very easy to layer over this one and basically stashes in your pocket when you don’t need it. This is a fantastic bit of winter protection.

However, because of the light weight of the cuben this is NOT the jacket for bush whacking. I suppose one could layer over it in rough situations.

And, RBH has great customer service and probably be able to customize almost any request. I'm very happy with my purchase.

Doug

Very nice!

+1 on RBH customer service and quality.

i was intrigued by these products too. What temp would you say they would keep you warm while hiking-less intense than running..

Ike

Many facets to your question. Kind of depends what you layer over and under the VB. Usually I go with a thin wool or Brynje polypro layer underneath. Everyones "comfort" experience is going to be a little different as well. And finally, probably the biggest factor is exactly what kind of energy expenditure occurs at your hiking pace. The body produces a phenomenal amount of energy while you are active - you can kind of adjust your "furnace" by adjusting your pace and energy output.
Having said that I used a single wool underlayer and RBH's NTS vapor jacket (slightly thicker than the cuben) during a 120 mile"race" in Northen Yukon last winter. I was doing a combination of very slow running and brisk walking and the temperatures went down to 50 below - warmest was 30 below and I was relatively "comfortable" with this. Of course the moment you stop moving that's a different story. So I wouldn't be too concerned with the lower end. The key is to adjust your energy output so you don't get too cold - or too hot and sweaty (that is where good vents make a world of difference). I wouldn't use the VB ABOVE 30F while hiking though- that would just be too hot.

Doug