Primaloft Bags?

[Colter]

I'm a big fan of down because of its light weight, loft, durability and comfort. According to my latest research, many folks are saying Primaloft matches down ounce for ounce as far as thermal efficiency, and of course exceeds down when wet.

I'm fond of the saying "extraordinary claims require extraordinary proof," so I'm skeptical of the Primaloft claims. What do you folks know about the relative merits of down vs. Primaloft?

[Footslogger]

Can speak personally for a bag filled with PrimaLoft but I did purchase a PrimaLoft pullover from MEC last year for my thru-hike. Have never been so warm and comfortable in such a light weight garment in my life. The pullover weighed around 11oz and when I didn't need it for upper body warmth I stuffed it into its own pocket pouch and used it as a pillow. On the coldest of nights I pulled it on over a long sleeve T-shirt and used it for sleeping.

I occasionally hiked in it although it was generally too warm to wear very long. It did often get wet with drizzle or mist on cold mornings but never seemed to loose it's insulating properties.

Based on my experience I can only imagine that a sleeping bag filled with PrimaLoft would be a very nice piece of gear.

[Peaks]

Coulter,

I found that most manufacturer's claims of equal ounce for ounce thermal efficiency compare their synthetic fill to 600 power down fill. Most of the lightweight down bags, like those made by Feathered Friends or Western Mountaineering, use a higher power fill. Thus, Primaloft probably does not have the same thermal efficiency as a Feathered Friends or Western Mountaineering bag.

Does this matter? If you are buying a summer weight bag, probably not, because the difference in weight of fill is very small. If you are buying a winter bag, then there is more fill, and thus it makes more of a difference.