By The Numbers: Fun Findings For Five Fuzzy Fabrics

[Stephen Seeber]

Companion forum thread to: By The Numbers: Fun Findings For Five Fuzzy Fabrics

Five fuzzy insulations get measured head-to-head: Polartec Alpha Direct, Primaloft Evolve, and three Teijin Octa builds. See how structure drives air permeability, MVTR, drying rate and energy, directional R-value, and durability. Results highlight Alpha’s breathability and efficiency, Evolve’s resilience, and Octa’s structured, durable use cases for high-output backcountry layering systems.

[Jerry Adams]

Interesting, thanks

When you measure the R value, do you put the fabric between two plates?  Or over a plate with air on the other side?

That is, does the R value include the air layer outside the fabric if it’s worn on the outside?

These fabrics have a raised grid with a void between.  That void gives a lot of insulation.  Do you have an idea how much insulation a void produces compared to a volume that’s occupied by fibers, like down or synthetic or fleece?

[Stephen Seeber]

Hi Jerry:  I use a guarded hot plate.  This device is open to the air, and the test fabric is laid on its heated plate. I measure the watts required to maintain the plate temperature during the test. This is divided by the difference between the plate temperature and the ambient temperature.  From the resulting number, the air film R-value is subtracted.  I measure the film R-value using the guarded hot plate.  If calibration and room conditions are consistent, this number won’t change.  The film R-value is .56.  If you want to know how this works, you can read about it here.

If you look at the data tables, you will see that some of these fuzzy fabrics have measurable differences in R-value depending on orientations. The difference is the way convection impacts heat loss depending on whether the open spaces are open to the air or contained by, in this case, having the open space toward the guarded hot plate.  In the real world, I don’t expect these open spaces to insulate as I measured them because they can be subject to moving air with every step you take.  The differences can be larger than the differences in the data table for fuzz up/down per gram of fabric weight.

[Robert Langer]

Hi Steven, thanks for the interesting tests!

I would have loved to see a comparision to a non-fuzzy conventional fabric in the charts. The charts help me to understand the differences of the fabrics discussed here. But they do not help as much to decide whether it is time (and worth it) to swap my current fleece. Maybe you could integrate a “standard conventional fabric” for reference next time? (I am aware that there are lot’s of standard conventional fabrics to choose from but I trust your expertise to pick a relevant one.)

One more question: how do typical “grid fleece fabric” (like in the former Patagonia “Non-Air” R1 pullover compare to the Teijin Octa fabrics? (If you have already covered this somewhere, please feel free to point me to it.)

[Jerry Adams]

” In the real world, I don’t expect these open spaces to insulate as I measured them because they can be subject to moving air with every step you take. ”

another study? : )

The R value of an air film drops about 25% at 2.5 MPH, a typical walking speed, so maybe it’s still a factor in the real world.

If you had the fuzzy fabric as a mid layer then it would be effective.  Like fishnet fabric.

That’s reasonable you subtract out the 0.56 R value of the air film.  Like you’ve said before, it’s confusing whether other measurements of R value take this into account.

[Stephen Seeber]

HI Robert:  Here is a discussion of fleece vs fuzz. The primary benefit of fuzz vs fleece is warmth per ounce of fabric. A secondary benefit is the vast air permeability for vapor removal. Of course, this is effective only if all your layers support moisture removal.  Fleece may be more resiliant that fuzzy fabrics.  Fuzzy fabrics do not resist crushing well.  When the loft is crushed, fuzzy fabrics no longer perform as expected. The loss of loft can lead to increased vapor condensation and wet fuzzy insulation. I have not studied this performance aspect enough and have not compared resilience between fuzz and fleece.

[Stephen Seeber]

Hi Jerry, the various standards for guarded hot plates use handle air-film subtraction differently. I subtract it out.  Leaving it in would greatly inflate R-value claims, especially for base-layer fabric, where the air-film thermal resistance can be much greater than that of the base layer.  You can read more about this issue here.  This discusses the concept of “intrinsic” thermal resistance, which is another way of saying to subtract out the air film.  Also, I would not rely on the thermal resistance of large air spaces in baselayers to remain stable.  Every time you move, pumping disturbs these air spaces in your layers.

[Jerry Adams]

I was just re-reading that the other day

“We can see there are different treatments of clo calculation and different definitions of intrinsic clo or intrinsic insulation. No wonder people find this topic confusing!

Why does this matter? The short answer is the potential for double-counting the air film resistance. Double counting will inflate the expected performance of the insulation for multiple ounces of insulation.”

Good points.  You are the only one I’ve found that deals with this explicitly.

Another question, I’ve always been confused by the term intrinsic clo.  I find places where they multiply the clo of a garment by percent of body area that it covers.  So, you can add up the intrinsic clo of pants, jacket, and hat, for example, and that will give you the average clo over your body.  But if you add to that the intrinsic clo of a mid layer then you risk double counting the air film.

So, intrinsic clo is affected by the air film, but intrinsic clo does not completely account for air film.

What you’re doing seems better – use clo (or R value) without air film, then add the air film insulation at the end.  Or better, you could have total body R value with and without air film so you’d know how it performed in calm and windy conditions.

[Stumphges]

Thanks, Stephen. Excellent.

[Stephen Seeber]

Hi Stump. You are welcome. I am glad to see you are still following things at Backpacking Light

[Paul McLaughlin]

Stephen – did you consider testing all these fabrics for insulation value with a shell layer over them?

[Stephen Seeber]

No.  The measurements are taken in still air.  Real-life use adds all kinds of thermal complexity to performance. The shell, in real use, would help provide somewhat still air.    So, kind of a wash. The shell provides a negligible increase in warmth, in terms of added R-value. Of course, if you are walking rapidly, or subject to wind, the shell will dramatically reduce convective losses that would occur in a bare fuzzy fabric.  I don’t know if that gets to your concern, so let me know if I am missing something.

[Eric Blumensaadt]

I faintly remember Polartec having a pile with hollow core fibers what were supposedly warmer. If I remembered wrong IS there a company making hollow core pile?

I know my alpaca socks are definitely warmer than equally thick sheep’s wool socks B/C alpaca fibers are hollow. I would therefore assume hollow core fiber pile is warmer than very similar pile without a hollow core.

[Eric Blumensaadt]

I wish a lightweight alpaca fabric could have been tested here. BUT alpaca must be combined with a synthetic fiber for ease of knitting due to the “difficult” nature of alpaca wool fibers working in weaving/knitting machines. That means if nylon is used it will hold more moisture than if polyester is used to make the weaving or knitting feasible.

[Terran]

I was using buffalo wool socks. They’d wear thin and the buffalo wool would dissipate leaving the synthetic knitting. I’ve read the same about the Hollow socks. Soft and warm, but wear out quickly. I’m wearing possum now, but I don’t expect them to last.

[Stephen Seeber]

Eric, as far as I know, there are no fuzzy fabrics made with Alpaca or Alpaca blends. I do have a fuzzy blend shirt made with wool and polyester. It was sent to me, and I don’t know much about it. I have spent a lot of time wearing it.  It is a 90 gsm fabric, and the performance characteristics that I can measure without cutting up the shirt are nearly identical to those of 90 gsm Alpha Direct.

I have never measured superior warmth from a hollow fiber.  Why is that? Consider that the volume of air in base layer fabrics is over 75% of the fabric volume.  The rest of the volume is made up of fibers. The base layer fabrics I am working with at the moment range from 80% to 92% air.  So, how much more air will you trap by adding a micron-sized hollow space in a fiber that might be 15-25 microns in diameter, constituting less than 25% of the fabric volume?  I don’t know the answer, but so far I haven’t been able to measure an impact on fabric R-value.

[Jerry Adams]

are you saying hollow fibers are a marketing thing?  : )

it’s never made sense to me like you said

[Woubeir (from Europe)]

I faintly remember Polartec having a pile with hollow core fibers what were supposedly warmer.

Funny enough they called it …. Aircore

[Terran]

I wouldn’t call hollow fibers marketing hype though there is hype in every market. Exaggerated perhaps in performance. Other factors come into play. I prefer the fluffy fabrics in most cases. I restrict the hollow fibers to my feet. Even then, they’re mostly a high percentage of moreno and synthetic.

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