Rab TILT and Similar Reflective Coatings Reducing Radiant Heat Loss in JACKETS

I suggest you start with this:  https://backpackinglight.com/forums/topic/evaluation-of-omni-heat-performance/   and this:  https://backpackinglight.com/forums/topic/by-the-numbers-if-you-carry-a-space-blanket-buyer-beware/

Hi Stephen,

thanks for the recommendations. I’ve reviewed the information you shared and it makes sense to me. I’m not a physicist or engineer but the logic and experiments seem sound.

Why do reputable companies continue to advertise this technology if the work you’ve done indicates it is not worthwhile? Do your experiments exhaust the subject? Why would they spend money on R&D for this if it is so apparently irrelevant to the performance of the garment?

Truthfully, I didn’t think much of it when columbia and others put shiny stuff in their coats, but as RAB as committed to this tech more it has made me wonder about it anew. In particular, RAB specifically claims to have tested the location of the IR barrier (closer vs farther from skin, facing in/out etc.) and they found that having it be closer to the skin was more effective. This contradicts your work, as I understood it. As a laymen, it leaves me confused.

Any thoughts on this?

I have no objective data, but my New Balance Fugu has shiny coating on the inside and it is a dang warm jacket. It also uses high fill power down, so that’s probably a bigger factor.

Hi Erik: There are lots of unfounded claims made by the active wear manufacturers.  I do my research and write about this all the time. I think it is called marketing.

Radiant barriers can work.  If they could put a low emissivity coating on the outside of a garment, it would function.  Sort of.  Inevitably, it would get soiled and become increasingly less effective.  Inside a garment, it is impossible to avoid contact with underlying layers.  Contact eliminates radiant transfer.  Further, the interior radiant barrier will deteriorate from exposure to body oils and other contaminants.  So, perhaps it is possible to develop a functioning radiant barrier. For example, a wearable Thermarest.  Seems pretty impractical.  When I find one that has any useful function,  I will happily write about it on BPL.

Stephen,

I think that makes sense. I don’t take manufacturers at their word, and I expect marketing spin and exaggerated claims, even logical fallacies. Perhaps this is a naive position, but I like to think it is less common for companies to completely fabricate claims.

What makes this such an egregious case is the surprising amount of detail   provided, including such things as: “After extensive R&D we found that positioning the layer of TILT as close to the body as possible maximised heat retention.”Normally marketing spin is more vague! I still find it interesting that they’ve claimed to have found differing results.

I suppose my question to you, Stephen, would be whether you can theoretically think of a way to understand these results? Or whether your position is simply that it is all more or less BS.

It is worth noting that the IR barrier is behind a 10D liner, protecting it from the skin, but not far enough, I’d guess, as to prevent conduction. Given that it does not appear vulnerable to wearing out, flaking off onto other layers, etc., I think my approach to such garments is to more or less ignore the layer. In the case of the rab jacket, it still seems like a nice coat regardless of the “TILT”.

I just watched this tilt jacket video.  In the video, they claim that the TILT scrim reflects up to 15% of body heat. (It is totally unclear what is meant by “body heat”. This is not a useful term to define performance of a radiant barrier.) Let’s assume they mean it reflects up to 15% of available radiant energy, which suggests an effective emissivity of, at best 85%.  Aluminum foil emissivity  can be around 5% (reflects 95% of incident IR energy).  The TILT scrim seems pretty crappy by comparison.  Of course, we don’t know how they came up with this value. Is this measured for the scrim fabric itself or the scrim in the jacket?  Now, they say “up to”.  So, how much reflectivity is present in normal use?  I would guess closer to zero.  In normal use, the scrim will be in contact with the liner fabric on one side and down on the other.  The scrim encapsulates the down.  The inner liner fabric provides an additional trapped air layer relative to conventional construction.  I would not be surprised if the additional air layer adds more warmth than the scrim.    If you look at their 20F sleeping bag that uses TILT, the EN standards testing does show very good performance for the listed fill weight and overall bag weight.  The Mythic Ultra 360 saves significant weight by using a 1/2 length #3 zip and 7D fabric.  Both the bag weight and especially the fill weight is strikingly low for the resulting EN temperature measurements.  If the published values are all correct,  this bag does show excellent EN results for its fill weight.  Is this because of TILT or some other construction technique.  I cannot tell.  I sent Rabb an email requesting some clarifications.    How can TILT work in a sleeping bag?  Not clear to me. The emissivity of non-oxidized titanium is greater than 50%.  So, it is not a great reflector in IR.  (Remember, a material that looks shiny to the eye, is not necessarily a good reflector in IR.) It is directly in contact with both skin and down, so it should have very limited performance as a radiant barrier.    Rab is going to make one available to me, perhaps next week to look at (no actual testing).  I will post whatever I learn.

Interesting to hear your take on it! I’m interested to hear if/what you learn from looking at it.

A few years ago, I spotted a Columbia wind jacket with the omni-heat dots. It was on closeout and it seemed like a cheap and easy way to compare to my existing wind shells. I wore it running and casually, to see if I felt a difference. I couldn’t. Even if it could have delivered 15% on some measure, it wouldn’t have made much difference to me. It might be slightly more wind resistant/less breathable due to the dots blocking some of the fabric. I’m glad I didn’t pay full price for the experiment.

Dear Experts,

apologies for somehow hijacking this thread but speaking about RAB’s new Mythic series (same of the new TILT jacket) how much warm in your view would add this new down jacket Mythic Alpine Down Jacket in respect to Arcteryx Cerium LT?

140 grams of 900 fill power down, no TILT (https://rab.equipment/eu/mythic-alpine-jacket)

I own the cerium lt but I find it pretty much useless for the my use-cases and the temperatures in the Alps.

Thank you and apologies again in case I shouldn’t have added here this question.

Hi Indrit:

I have no idea.  The Arcteryx website does not even provide the amount of down in the jacket and to complicate matters farther, they use two different weights of synthetic insulation in addition to down.  I have never tested one to measure R value.  All we do know is that the weights of the jackets, with hoods, are similar. They both use 10 Denier face fabrics.  Based on that, I would guess that you should not expect a significant performance difference between the two jackets.

I have seen charts indicating the cerium lt has 102g of down in a size medium. That is in addition to the synthetic insulation. So a bit more down on the RAB jacket, and slightly higher fill, but likely not a night and day improvement.