For a NOLS Rocky Mountain course this summer. Synthetic is required for use over 60 - 70 nights under a tarp-like setup at high altitude. NOLS asks for 5 - 10 degrees, 6" to 8" of loft, 3 pounds of synthetic fill.

I understand why they require you to have this specific setup compared to a down bag. But I have no experience with this kind of bag. I have never done a high altitude multi week trip like this. What is the smart light synthetic setup? Mountain Hardware Lamina? Integral Designs North Twin? Big Agnes Yellow Wall or Savery? Or some other bag?

I need to decide and get this bag in here ASAP. Any ideas would be greatly appreciated. If you have personal favorite, a bag you have your eye on, or a second hand bag to get me by, let me know.

I'd get something with Climashield XP. It's almost as warm per pound (highest CLO value) as Primaloft One (PLO), and warmer per pound than than Primaloft Sport (PLS). But XP will be more durable (retains loft) better than both PLO and PLS after stuffing it into a stuff sack 2.5 months in a row. And, XP doesn't need to be quilted to scrim to stabilize it like the 2 Primalofts do - so total bag weight is often about the same for XP as PLO.

On the other hand, Primaloft is a short staple insulation, whereas XP is a continuous fiber, so PL stuffs to a smaller size and this could be critical if you are carrying all the NOLS food, gourmet cooking setup, books, etc. PLO also drapes a bit more (is less stiff) than XP, but XP is no worse than 3-D was.

When I compare bags from different manufacturers, I'm usually looking at similar shells, shoulder / hip girth, and zipper lengths since I know how worried I am it will get wet (ie: tent vs tarp) and how hot it will be (no zip vs full zip). So, the difference in weight is essentially due to the amount of insulation (ignoring small variations in the curvature going from the hip to the feet different bags use). If they are the same type of insulation, then it's simple to compare the bags, otherwise you can use the CLO values for each type of insulation and calculate comparative warmths (search on CLO and you'll find lots of info, or goto thru-hiker.com and read the sales paragraphs on the insulation pages).

The primary reason the NOLS course requires a synthetic bag is for insulation maintenance when wet: down looses ~60% of its insulation when wet; Climashield looses ~40%; and Primaloft One looses less than 10%.

Edited by richard295 on 05/07/2008 09:57:46 MDT.

Richard,
Have you seen any tests on CLO retention after repeatedly stuffing XP vs PL One into typical stuff sacks &/or compression stuff sacks ? I wonder if PL Ones lesser loft retention "after repeated stuffing" would make up for the 30% difference in "CLO when wet" pretty quickly.

Edited by JohnG10 on 05/07/2008 10:12:50 MDT.

John,

Scientific studies showed the correlation between loft reduction and insulation loss was ~ linear in Primaloft. Also other synthetic insulations, using a mix of thin and thick fibers, had similar degradation patterns to Primaloft. By contrast, the thick fiber Polarguard variants lost less insulation value for a commensurate loft reduction.

Climashield achieved its increased insulation value versus Polarguard primarily by adding fine fibers to the exclusively thick fiber mats it previously used. Secondarily the mats are now wavy shaped. Theoretically, Climashield’s correlation between loft reduction and insulation loss should now be similar to Primaloft's because the thick fiber / thin fiber ratios are about the same.

By not tightly stuffing either insulation, their loft reduction should be inconsequential during the NOLS course.

HI E.H. check out Integral Designs synthetic sleeping bags North Twin model is rated to about 10F and has about 4.5" of insulations (I assume it's the top half they're measuring)

too bad Moonstone doesn;t make synthetics anymore, they used to have a fantastic 10F model which was a cooker...

Mountain Hardwear Ultralamina series Ultralamina 15?

Edited by LithiumMetalman on 05/07/2008 12:26:40 MDT.

Richard,

Do any of the scientific studies that examined CLO vs loft loss state how many compression cycles and how much compression force was used ?

Several people have posted replys to other questions saying that they estimate that their Primaloft bags lost about 35-50% of their loft after 1 year of sporadic normal backpacking enthusiast uses. However, I didn't get the impression any of them actually measured the before/after loft, nor did they accurately record the number of nights they went backpacking...

I'd be really interested in Primaloft and probably recommend it to all the Boy Scouts & college students if it retained 90% of it's warmth after 5 years of "sporadic normal backpacking enthusiast use". Since that amount of use varies, let's define it as 430 compression cycles (5 years of two 3-night weekend trips per month plus two 7 night hikes per year).

John,

Scientists generally measure loft degradation using an industrial washing machine set to a heavy duty cycle. They make up approximately 1 ft2 samples of each insulation type including its face and lining fabrics and use the same quilting method. They use a large cotton towel in the washing machine to act as the compression force. Every x number of complete washing cycles they measure the loft reduction in the samples. My recollection is that using this methodology, the class of synthetics using a coarse fiber, fine fiber mix, similar to Primaloft or Climashield loose approximately 30% of their loft after 10 wash cycles and then tend to stabilize at this level. My personal experience tightly compressing a Polarguard Delta bag one year and Primaloft Sport bag another year during multi-month kayak expeditions yielded the same results… each insulation type’ loft was reduced approximately 30% and then stabilization. After the washing machine loft reduction, the guarded hot plate clo tests showed that the coarse / thin fiber mix insulations loss is in general proportion to their loft loss. In other words they loose about 30% of their initial clo value after extended use. The Polarguard insulations are comprised of all thick fibers. This yields poor IR blocking and a relatively low initial clo value. After the Polarguard loft breaks down by 30%, the IR blocking improves enough to largely offset the conductivity loss resulting in only an approximately 10% clo loss after extended use.

Down or Polarguard, with reasonable care, should meet your criteria for 90% clo maintenance over five years use by a scout. Neither Primaloft nor, theoretically, Climashield will limit its clo loss to 10% after five years of use.

Thanks for all the quick replies. I spoke to Evan Jones at Integral. He actually recommended we get the lighter Renaissance and use it with the Integral Primaliner we already have. The combo is just a little heavier, warmer, and will give more options to use it later, at lower elevations this summer, and individually after the course. They are designed to work together and you can use the Primaliner as a pillow otherwise. The combo is warmer than the North Twin and well within the NOLS constraints.

Skip Clemmons

Edited by sclemmons on 05/07/2008 19:34:09 MDT.