Synthetic Insulation Degradation Part 2: Thermal Performance vs. Compression

[Stephen Seeber]

Companion forum thread to: Synthetic Insulation Degradation Part 2: Thermal Performance vs. Compression

How bad does high-loft synthetic insulation (Climashield Apex and Primaloft Gold) degrade when subjected to repeated compression cycles? What’s the impact on backpacking gear and apparel?

[James Marco]

Well, I pretty much agree with your tests and graphs, but I disagree with the statements made in your discussions. Yes, I understand the data becomes increasingly more cyclic. But, your statement 1 bothered me.
You said:
” Synthetic insulation degradation measured by thermal resistance decreases roughly 2% per compression cycle for Climashield Apex and 1% per compression for Primaloft Gold. Based on the trend equation, Climashield Apex will lose about half its insulation value after 60 compressions. Primaloft Gold will lose about half its insulation value after 164 compressions. The low R2 on Primaloft Gold means this is a very weak estimate. The moderate R2 for Climashield Apex means that trend provides a more dependable estimate.”
OK, even given that the Gold is a weak estimate, it looks to be better in the field. Getting this down to practicality, your tests suggest a half-life of 60 nights for Apex and a half-life of ~160 nights for the Gold. Since I am normally out 45-60 nights per year, I do not expect either to be worth the effort of the additional weight compared to down. (Yes, synthetics are much improved, but still fall well short of good down; normally, a half-life of about 300 nights or about 5 years at my usage.)
You said:
“Synthetic insulation degradation measured by loft decreases about 0.2% per compression cycle for Climashield Apex and Primaloft Gold. Thus, there is little change in loft after the 12th compression for Climashield Apex and the 7th compression for Primaloft Gold.”
I cannot disagree with this. 50 years ago I used some synthetic bags filled with Holofill. They lasted about 15nights, then I started getting cold at their rated temps. Each time I backed them, they got worse. Looked great, but they lost all their loft after one season. I got a pair of 0F bags ($15 each) that just were not worth the dollars. At the end of the summer, they left me cold at 32F.

[Eric Blumensaadt]

This is a good investigation with objective analysis and well documented. Thank you for this body of work. I’ll still take Climashield over Primaloft Gold after a horrible one summer experience with a Primaloft sleeping bag in the ’90s.

[Penny Vann]

Thank you for doing this study. I am wondering in most of the tests you allowed a recovery period between cycles, but how much real-world recovery does a bag get if hikers are using compression sacks? For instance: A hiker puts his bag in a compression sack. At camp, the hiker rolls out the bag and gets in it after dinner. The total recovery time for at least the back of the bag is maybe 1  in every 24 hour cycle times the number of days they are out. So, how does the amount of recovery over time influence the thermal performance?

Sorry if you covered this

Reverse

[James Marco]

Penny Vann:
According to the author(in the last line of conclusions:)
“In our next (and presumably last) installment on this project, we will perform crush tests of insulation that is stuffed into stuff sacks and then crushed. This will investigate synthetic insulation degradation by measuring the impact of bending the insulation fibers during the crushing process.”
I assume that none of the tests were performed on any real life backpacking trips. In fact the first article the author states exactly that, he just compresses stuff laid out flat. He has NOT finished the last test. The last test was stuffed in sacks but not compressed at all, he mentions about 0.88lb/in. This would be stuffing randomly into a stuff sack Most people use some sort of compression sack, either the one that came with the bag or another one (like an eVent 6×14 bag,)then compressing as tightly as possible by hand. Assuming a standard 6″ diameter eVent stuff sack (four straps at roughly 50lbs max which is well under any degradation of down,) will yield about 200lb at ~28.25″ or ~7lb/sqin. This will vary a lot depending on the hiker, of course. I would expect between 3-4 pounds/sqin to be a rough average or roughly a 20-30 pound pull on the straps. I suspect this will really destroy the warmth of any synthetics, but I will wait for his results.

[Stephen Seeber]

Penny:  Typically, I provided 12 hours for recovery.  However, based on visual observation, both types of insulation seemed to fully loft very quickly:  typically, when I took the samples from the crushing location to the recovery location, just that little bit of handling seemed sufficient to get to full loft.    The speed at which the samples decompressed was always impressive.  I don’t really have a specific answer other than that anecdote.  There will always be lots of permutations on abusing insulation that I will be unable to test systematically.

Eric:  When I started this study, I expected that Primaloft would fail faster than Apex.  That seemed to be the common wisdom.  So far, what I have found is that they perform very similarly.    For 6 osy samples, the Primaloft is thinner and more supple and the Apex is a bit warmer.  Things may change in the stuff sack testing that is now underway.  However, at this point, I think one would select one or the other for characteristics other than durability.

 

[Mark Verber]

Do you have an indication the relative impact of the compression itself as compared to the duration that the material is compressed?  For example, if you have a synthetic puffy which regularly gets taken on trips, but only occasionally is used, would it be better to leave it in it’s stuff sack, or compress and decompress after each trip so it’s being stored in an uncompressed state?

[Stephen Seeber]

Hi Mark:  Everyone is asking questions that show how little I have learned from this exercise!  I have reduced the cycling time in the present test but I still don’t think that will answer your question.

[james raynor]

thank yout for good information always

and the summary of conclussion

that would help non-englisher people like me

that made me happy

without it i should spend a lot of time again

i read your last writing do moisture wicking fabric work for 4hours

even with help by chrome

[Author]

Posts