By the Numbers: Thermal Performance Measurements of Synthetic Insulations

[Stephen Seeber]

Companion forum thread to: By the Numbers: Thermal Performance Measurements of Synthetic Insulations

Stephen Seeber presents measurements of several market-leading insulations along with four performance metrics to help judge their performance.

[Eric Blumensaadt]

My first experience with Primaloft was in the ’90s and it was a VERy bad experience with my bag’s loft disappearing after one season.

 

[Max Neale]

> “Utilization of insulations in garments may have substantial impact on actual thermal performance that exceeds the differences in measured thermal resistance performance.”

The main conclusion appears to be that the lab data generated here should largely, if not entirely, be ignored when making a decision about what jacket to select for a specific application.

Will BPL be updating the synthetic insulated jacket State of the Market Report based on extensive field testing?

[Stephen Seeber]

Eric–From the little historical data I could find, and as stated above in the article, the trend over time for Primaloft has been to increase the share of higher diameter fibers and reduce the share of small diameter fibers.  This should improve the resilience of the matt  but will reduce the insulation value.  I don’t think I will ever have the opportunity to determine whether such objectives might have been achieved.

Max–That conclusion was not my intention, but I can see how it follows.  My point was simply that after you install the insulation between two fabrics, sew, baffle and quilt the insulation into place, it will likely never again achieve the full loft that is present during the guarded hot plate test.  So, the lab numbers are the best I expect you can do, subject to the manufacturing variances that are discussed in the article.

I cannot answer your question about the State of the Market Report.  You will have to speak to management about that.

[Jerry Adams]

when I look at batts of Apex insulation, there are some places with more fiber, and some with less, even maybe a hole.  For the 2.5 oz/yd2 weight.  It’s probably not as bad for heavier weight insulation.  I try to find an area that looks better for my project, and leave the lower density areas as scrap.

I think that’s consistent with your observation.

Maybe one could sandwich two layers which would average out the density.

Nice article, thanks.  You have all the good equipment : )

[Stephen Seeber]

Hi Jerry:

Thanks for doing a lot of reading.  I understand that DIY sleeping bag makers  will  double layers in the hopes of getting better consistency with Apex insulation.  I don’t know how the commercial manufacturers deal with the issue.

[Jerry Adams]

yeah, a lot of things work for DIY that don’t for commercial

[K. Urs Grütter, LL.M.]

Thanks for the comprehensive work! And many thanks for the disclosure of the “starting points”! This is what many “scientific” reports are badly lacking. You can prove everything scientifically if you choose the proper starting points –  which may be vastly irrelevant in real life, but the sponsor/buyer of the study wants a certain result.

A little real life example: My wife used to be a bit chilly under our MYOG synthetic quilt, and continually tried to wrap it tighter and tighter around her, until I really explained her how the quilt is supposed to work and that she has to leave it loose in order to give it as much loft as possible. Problem solved.

Looking forward to the wet/damp analysis! I am quite astonished at how much perspiration I exude into my insulating layers even if I am chilly. And if it’s cold, this perspiration condenses inside my quilt. This is my main problem, and this is why I am converted to synthetics. I do use a western mountaineering nano lite down quilt on top of my synthetic one for additional warmth, but I would never consider going on down alone. Therefore, a comparison of down and synthetic when damp would be quite interesting…

Thanks again!

Urs

[Stephen Seeber]

HI Urs:

Thank you for reading the article.  I am working on the issues you raised.  It will be a while before down gets incorporated into these studies, but the method I have come up with for the article that I am now writing will work well on down.  The challenge going forward will be to distinguish between degrees of “damp” and “wet” and loss of thermal performance.  So, stay tuned.

[Peter S]

Interesting to read that one of my favorite jackets; the Rab Alpha Direct is such a dog in testing.

[Stephen Seeber]

Hi Peter:

Thanks for your comment.  Rab has been selling that jacket for years, so, I think there are many thousands of people around the world that share your opinion.  My comments were based on use on fast winter hikes in the Adirondacks.   It turned out to be too much jacket for that activity for me.  What I wrote was not based on lab testing, it was based on use.  I am working on an article on “Active Insulation” jackets.  When that article is published, and in comparison with other active insulation jackets, it will be seen that the numbers explain my experience.  But, enough about me.  Any of these garments that have a long sales record are meeting the needs of a particular constituency and understanding what works and when is why we participate in these discussions. If you want to share your experience with this jacket, it will provide readers and me conditions under which this jacket is working well.

[Stumphges]

Fantastic!

What a tremendous amount of work. Thank you, Stephen.

 

Quick note about the rendering online and in converted PDF format: At least on my end, Table 6 is too wide, with one or more columns of information lost off the L margin of the page. When I convert to PDF view those columns are indeed lost off the side of the page.

[Stephen Seeber]

Hi Stumphges.

Thank you for reading.

I understand your concern about the tables.  They are hard to read as published.  I am hoping this issue will be corrected in time for my next article. It is being worked on. Kind of hard to see, but there is a scroll bar on the bottom which provides horizontal scrolling.

[Geoff Caplan]

Stephen – hearty thanks for an outstanding effort! I’ve only just found the energy to roll up my sleeves and work through it. This is the kind of work that makes BPL uniquely valuable.

On Alpha Direct, I agree that encasing it in a shell fabric doesn’t make much sense.

My understanding is that the original brief from the Army was for a mid-layer that infantry could leave on in a wide range of conditions – I’d imaging that changing clothing in combat is something you’d rather avoid!

I have the Rab Flash (picked up in a sale – the price is painful) which is a jacket using “naked” Alpha Direct. The only shell is a couple of patches over potential wear points, because it’s not the most robust of fabrics.

https://rab.equipment/uk/alpha-flash-jacket

I find it works very well.

It’s half the weight of an equivalent fleece, as you say, it wicks like a champ and it dries very fast.

When it’s moderately warm, I use it uncapped and because it’s so impermiable I don’t overheat, even toiling uphill. Mind you, hear in the UK there’a almost always a bit of cooling breeze around.

When it gets chilly, I cap it with a windshirt or hardshell and walk very comfortably into sub-zero temperatures with just a thin baselayer.

So in anything short of blazing heat I can wear it continuously through the walk.

Which is just as well, because it’s quite a “clingy” fabric and not the easiest to get on and off over a baselayer.

[Geoff Caplan]

Oops – can’t see a way to edit. When I said that Alpha Direct is impermeable, I of course meant permeable…

[Stephen Seeber]

Hi Geoff:

 

Thank you for the kind thoughts.  I know these articles take some work to get through and I am glad you found it worthwhile.  I suggest when you find the time you go through the first deep dive article.  It discusses a lot of fundamental issues with synthetics and provides performance numbers for market leaders.  Concerning clingy:  It can be annoying to put Alpha on or remove it,  particularly over a base layer.  My take on clingy also includes this thought–When you put it on it clings to you as well.  It seems to eliminate air spaces between itself and you.   This makes it feel really cozy in a way that typical synthetic batt insulations garments cannot.  This feature was important in my decision to start using this as a mid layer, and occasionally, an outer layer where conditions permit.

 

I see the edit function is now working.

[Geoff Caplan]

Hi Stephen – not stalking you – you happened to post just as I was checking in!

Interesting thought about the clinginess of Alpha Direct – it’s clear now you’ve pointed it out. It drapes better than any jacket I’ve ever used.

Batted insulation doesn’t drape nearly as well, obviously. So as you move there’s quite a lot of air circulation between your base or mid layer and the batted garment. I’m no engineer, but I suspect that must be moving heat away by convection, especially as you have leaky seals around the wrists, neck and waist.

With the Alpha, it’s about as snug a fit as you can get. So the warm air is trapped right against the lower layers provided it’s tightly capped.

Combine that with the fact that it wicks *far* better than any batted garment which helps your base layer to function, and it starts to be clearer why it seems to give such good warmth for weight despite it’s wispy appearance.

Or am I misunderstanding something? This isn’t really my field.

[Indrit S]

Hey @StephenSeeber,

I just got the upgraded premium membership to have access to your articles and posts. 😊

Thank you very much for these. Please continue to share your views.

Indrit

ps: I’m still waiting for your membranes MVTR article though…😊

[Stephen Seeber]

Hi Indrit.  Thank you for the kind words.  There are three MVTR articles in the pipeline.  One, on the importance of MVTR performance,  was just submitted.  On the other two, I am adding more garments to each article.  So expect lots of product specific data on this subject.

[Scott W]

A lot of great work here! One note, it does not look like you have any moving air over the test subject. I think specs require .5 to 1 m/sec air flow. This helps keep radiation from being very dominate. A simple house fan will work. Put the scrim side up to block the air flow or better yet a light ripstop over the insulation to block the flow if you are worried about air entering the insulation. – Scott

[Scott W]

I have conducted similar tests as you have and have done similar calibration checks with various materials like cork and different foams, some as thick as 2 inches to confer my method. It looks like Primaloft uses ISO 11092 for their testing. That method does correct for air film resistance so it should be ok but I too cannot come close to their claimed numbers. I get close to an R value of 2 for my 6oz/yd**2 sample.  This is lower than yours but my sample is about 1 oz/yd**2  lighter than yours with scrim and was severely compressed by being shipped in a vacuum pack for shipping. Its thickness is only about .52 inch under about a .0023 psi load after being released from the vacuum pack for about a day. Going to the TESTEX website it gives the general nature of ISO 11092 testing . It shows that corrections are needed for samples over 5mm in thickness. My method also uses a correction for thickness. Because the thickness of the Primaloft material is much harder to define than that for a foam or a cork I am wondering if this is part of the problem. Your method is a little different since the test sample fits into a cavity and does not lay on a plate so the spreading in the test sample is different. It looks like your plate is around 9×24 inches so spreading would be different than my setup with a 10×10 inch heated plate. Still a mystery

[Jerry Adams]

if there is no wind, then there’s an air layer on the outside that adds a fraction of an R

1 m/sec is about 2MPH which I have noticed is enough to mostly eliminate that air layer

it wouldn’t be correct to measure the apex and include the air layer.  In the real world it’s windy so you don’t have the air layer.

[Stephen Seeber]

Hi Jerry:

The guarded hot plate method measures heat loss from the bare plate, before measuring insulation with the insulation placed on the plate.  This accounts, more or less, for convective and radiant  losses to the ambient for the test setup.  This value is subtracted for heat loss for the insulation mounted on the plate.  This subtraction provides the inherent R value of the insulation only.   There are standards that incorporate both moving and still air.  This can be done either way and should yield about the same results as long the tests are done consistently.

[Jerry Adams]

I was just adding to what Scott said on March 1.

I see what you mean about subtracting the bare plate temp.  That makes sense.

[Stephen Seeber]

Hi Scott:  I sent a reply and it disappeared.  In any case, let’s continue this discussion by PM.  Just drop me a  line.  The discussion is clearly bound for the weeds and may not be of much interest to most people.

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