A New Paradigm for Understanding Garment Warmth

Michael,

Thanks for the positive words. You said, "How does Polartec's own "thermal pro" compare to Polartec's traditional fleece at the same fabric weight?" I haven't tested it to verify their claims but their specs claim, Polartec 300 = .007 TOGS g/m2, Thermal Pro #4060 = .010 TOG g/m2, and Thermal Pro #4082 = .011 TOG g/m2.

I've always wondered why people don't also consider the heat sink effect of different materials in clothing. In buildings the R-value of a material can affect the temperature sensation of a room; even though the air in the room may be the same temperature, the materials used in the walls and the floor, when touched, can make the room feel cold or hot. That's why, on a cold day, rooms with wooden walls and floors tend to feel warmer than rooms with stone walls and floors. Some of the jackets that I have when I touch the outer nylon fabric feel much colder to the touch than others. There must be some effect of this heat sink sensation on the outer fabric, contributing to the overall feel of the warmth of the jackets.

Michael,

After waking up this morning, I thought about my response to your question about how Thermal Pro compares to Polartec 300 question some more. I think there is a clearer way to answer it. It is apparently frequently asked because it is one of the Thermal Pro FAQs: What is the difference between Polartec® Classic and Polartec® Thermal Pro®?

“…We have specific thermal data on each Polartec® Thermal Pro® fabric but without knowing which Polartec® Thermal Pro® fabric you are considering, it is impossible to rate it against Polartec® Classic 200 or Polartec® Classic 300. Each Polartec® Thermal Pro® fabric is developed to meet the expected functions needed for a specific use.”

I think the clearest answer is that they specify both Polartec 300 and Polartec Pro at .16 clo/oz/yd2. Polartec 300 is 10.9 oz/yd2. Common Thermal Pro fabric options are 6.9 oz/yd2, 7.1 oz/yd2, and 9.4 oz/yd2. To compare their loftiest Thermal Pro version to Polartec 300 multiply both fabric clo/oz by .16. Comparing the ratio yields 14% less warmth for the thickest version of Polartec Pro. It is a much loftier and compressible fabric and so it LOOKS MUCH WARMER and compresses much better for stuffing in a back pack. I haven’t tested any Thermal Pro garments and so this is theory only.

Tom,

I haven't tested the insulation of Under Amour’s products because they fall primarily into the category of base layers and it is very difficult to get an accurate measurement of insulation that thin. Base layer insulation tends to be of less importance than that of most clothing items, its tactile properties, and the way in which it handles moisture, are of much greater concern since it is in direct contact with the skin.

It is really difficult to get an accurate measurement of base layer insulation based on standards procedures. The usual American Society of Testing Materials (ASTM) method for thickness measurement requires compressing the material by 0.7 g/cm2 (.01 psi). This very mild level of compression is still sufficient to compress the fibrils at the surface of the material and these, although very compressible, do contribute to trapping additional surface air film thickness. If one uses a method where thickness is measured without any compression the measured intrinsic insulation will approximate the insulation predicted using 1.57 clo per centimeter (4 clo per inch).

The insulation of base layers is seldom a major consideration in thermal comfort, since it lies within an already trapped still-air layer between the skin and the outerwear. Indeed, static copper manikin measurements of a clothing system frequently give the same insulation measurement with or without a base layer. Nevertheless, a thicker base layer will contribute warmth in the presence of wind or body motion, particularly if the outerwear is not totally windproof, the closures are not tight, or the clothing is compressed by the weight of outer clothing layers or back pack.

A base layer’s insulation over the torso will generally be close to that approximated from its full uncompressed thickness. This is because of the air gaps between the underwear and the clothing worn over the torso. However, the insulation over the arms and the legs will be closer to that suggested by the compressed (ASTM) thickness measurement as a result of the closer fit of the outer garments.

Jonathon,

I haven't tested any Climashield Green garments but Polarguard Delta is specified at 3.06 clo/inch and Climashield Green is specified at 3.25 clo/inch. We can view them as equivalent.

40% of the Climashield Green fibers are recycled polyester and they have to be thicker than virgin fiber for the same strength. This is why Green is much less thermally efficient than XP.

Michael F.,

The garment's torso is tested with a guarded hot plate to ascertain its insulation value. I tested a Patagonia down Sweater vest and determined its intrinsic clo was ~2.31. I also tested a Patagonia down Sweater Pullover hoody and determined its intrinsic clo was ~2.31. The insulation, fabric, and construction although slightly different between the garment types, yielded the same ~intrinsic insulation value. Total clo, for each garment, is determined by multiplying the intrinsic clo by the body surface area that it covers. The average body surface areas (BSA) covered by different garment types are as follows:

Hat 4%
Shoes 7%
Balaclava 8%
Pants 43%
Shirt or Jacket 48%
Hoody 54.5%
One Piece Suit 80%
Sleeping Bag 98%

If you want to compare the total clo between two dissimilar garment types (for example the Fugu jacket and the Permafrost Parka), multiply the intrinsic clo value times the BSA for each garment to determine how they compare. The Fugu total clo is .48 * 6.18 = 2.97. The Permafrost total clo is .55 * 5.24 = 2.90. The hood on the Permafrost is huge but a down balaclava, in combination with the Fugu would easily beat it for greater warmth at less weight, save the relative durability issue.

My objective for this thread was to provide a very simple way to understand the relative warmth of different types of garment’s insulation. It was not to provide the total clo value for each different garment type and insulation type. None the less, for any body so interested, the above BSA values allow you to calculate ~total clo.

Adrian,

Thanks for the kind words. The Power Dry and Power Stretch garments are hybrid base layers/insulation layers. They need the stretch fibers to facilitate the base layer functionality only. For use on trips like Erin and Hig's coastal hiking/packrafting adventure the material gets good reviews. It is probably too heavy and warm for most UL backpacking applications.

"Tom,

I haven't tested the insulation of Under Amour’s products because they fall primarily into the category of base layers and it is very difficult to get an accurate measurement of insulation that thin."

Richard,
Many thanks for the information. I am in the process of trying to further reduce the the clothing component of my base weight, and you have likely saved me considerable time and expense. Your insights are always appreciated.
Best regards,
Tom

Tom and Huzefa,

Please post a link to your article after it is published. Particularly in the realm of WPB fabrics you have provided many well researched posts. I have no doubt that your article will be of similar quality.

Comparing options without making things too complicated was indeed the objective of the graph and this thread.

Huzefa – In line with those objectives, I hope that you understand that old forum posts that went into a much higher level of technical detail won't be discussed by me in this thread.

Lynn,

Thanks for the kind words. I have been contacted by a forum member in the Bay Area. He will provide a WM jacket and vest. I will add this info. If someone in the Bay area has a Nunatak Skaha to loan for a test, I will also add that info.

Tom K,

Great question regarding the breathability trade off of increased down density. I don't know the answer but, I will try and check to see if there is any published research that answers that question.

Richard,
That would be much appreciated by the proud owner of a WM Ultralight with 2 oz of overfill. I think it probably was a good idea, but this question has gnawed away at me off and on over the years. I haven't had it out on trips over 11 days and those were in the Sierra in late Sept-Oct, where it worked fine. Winter trips are another question entirely and the results might well be different if I miscalculated the tradeoff.

Chris,

I appreciate your experience based contributions to this topic. I suspect we have more common ground in our insulation views than our respective posts might lead others to believe. The same insulation types and similar densities will indeed thickness correlate with the warmth of garment. It is the exceptions in down density, down fill power, or differences in synthetic insulation types where anomalies occur. I am sure that there are one or more people in the forum audience who will peer-review at least some of the anomalies I pointed out. As these additional peer-review tests are published, we will both gain additional insights that will allow us to achieve more common ground.

Richard, I'm sure we have much in common and I appreciate your posts and information. I am trying to correlate your information with my experience. The down density issue particularly interests me as I have not come across this before.

With regard to down fill power and synthetic insulation I have come across many anomalies, especially with the latter. And not just between different synthetics but between apparently identical bags with identical insulation. Synthetics are not uniform. Overall I've found synthetic bags – and I've tested dozens over the years – to be over-rated, some scandalously so. I'm a warm sleeper but have yet to find a synthetic bag that keeps me warm at the claimed temperature rating. With many down bags I am warm below the lower temperature rating. I have raised this with synthetic bag makes occasionally – replies I've been given include "we know serious users don't use synthetics so the temperature ratings are just to make the bag sound good", "we know the bag isn't warm at the claimed temperature rating but our competitors claim the same for similar bags so we can't change it" and "we have no idea what the actual rating is – we just copied what other companies said about similar bags".

>If someone in the Bay area has a Nunatak Skaha to loan for a test, I will also add that info.

If no one volunteers, I might consider mailing one to you. The postage costs would be outweighed by the knowledge gained for the BPL collective…

Richard,

Thanks once again for this superlative post that will lead us to many excellent purchases for our gear closets and to the "gear swap" forum to make room for those purchases :-)

I think you covered some of this in your response concerning Under Armor base layers but I'll ask anyway. I use merino wool base layers but, I have some very heavy 320 and 390 weight for winter use. They feel very warm and cozy to me, but I suspect, some of that is due to the other properties (wicking, etc) that you mentioned concerning base layers in general.

My question is, at these stout thicknesses of wool, can you determine their insulation properties, as I have been wearing them as insulation, not as a base layer, although I think they function as both?

Even though these wool garments are heavy, I have preferred them for hiking over my Micropuff or my Montbell Alpine Down as I don't view these as durable enough with their thin shells, or synthetic insulation crushed by the pack, or down absorbing all my sweat. I have limited these "puffy" garments to rest stops and camp or to augment my sleeping bag. But, should these wool garments show that they don't really insulate well, maybe I should reconsider my choices.

Michael,

In summary, don’t change a thing.

The heavier Merino wool base layers, as well as the Polartec Power Dry and Power Stretch fabrics, serve a hybrid role. They address the base layer function plus adding insulation beyond what is required for a base layer. The complex weaves and bi-component nature of the aforementioned Polartec products make simple estimations difficult. On the other hand, the thicker Merino wool base layer’s insulation value can be accurately estimated. Measure the uncompressed thickness in inches and then multiply this value by “4 clo/inch” to determine where they are positioned in the insulation graph.

If you are thermo neutral (not uncomfortably cold or sweating) when hiking in your heavier Merino wool garments that is an excellent combo base layer/insulation solution. When you are hiking, you will be typically average in the range of 7 METS. You will only require additional dedicated insulation when your MET level drops significantly. While hiking, you will subconsciously vary your pace in an attempt to stay thermal neutral (not cold or hot). For the same effective temperature that you were comfortable hiking, you will require ~7/1.5=4.7x more insulation when doing camp chores. That activity is typically the province of the dedicated insulation garments.

Thanks once again Richard!
Now I feel both physically and academically warm in my wool!
:-)

Richard,

As for your Montbell figures,i am a little confused by a former post published by you Nov 28th 2008 (not so long ago)from which i deduce that the MB Alpine jacket CLo would be around 2-2.2 , ie quite lower that what is shown in your nice graph. pls see below

François

own a Mountain Hardware Sub Zero with sewn through construction. It weighs 27 oz in size medium. This is primarily because the external fabric is 55 denier, the liner is 30 denier, and the insulation is 650 fill down. Mountain Hardware doesn’t publish the down fill weight or the clo value of the jacket. Also there is no other independent source that has published the clo value for this jacket. I tested it in my lab and it yielded an intrinsic clo value of 4.477. To put that number in perspective it is more than double the warmth of the Mont-bell Alpine jacket which is Mont-bell’s warmest light weight down jacket. The MB Alpine was also tested by me. The MB Alpine uses 800 fill and box baffles. The MH Sub Zero is an excellent jacket if you require that level of warmth in combination with extreme durability. Equivalent warmth in a jacket using 800+ fill down and lighter fabrics will require ~ 9 oz of 800+ fill

Francois

The most recent chart I published showed the intrinsic clo for the MB Alpine jacket to be 3.769. The Mountain Hardware Sub Zero tested in the same battery of tests yielded and intrinsic clo of 4.521 versus 4.477 in the earlier November test. This makes the Mountain Hardware Sub Zero approximately 20% warmer than the MB Alpine not 200% warmer as was stated in my November 28, 2008 post. I made a mistake in the November post. Thank you for a great job of consistency checking. I have now corrected the November 28, 2008 post to reflect the correct warmth relationship.

The updated November 28, 2008 post is located at http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=16819

Richard,

MH quotes 261g of down in a size L in the Sub Zero jacket and 364g in a size L of the HOODED Sub Zero jacket.

Since they don't offer hood/jacket breakdowns, how much of that 103g difference is placed in the hood in a logical opinion?

Also….are these SubZero jackets warmer than the Phantom (197g size L x 800)?….

I also wonder if a 200g Primaloft jacket could compete with these jackets for warmth…..I keep reading about people using these jackets in 0F degree weather YMMV of course…..

David,

To recap, my laboratory tests showed that the MH Sub Zero jacket with 9.2 oz of 650 fill down was approximately 20% warmer than the MB Alpine jacket with 6 oz of 800 fill down.

The down, normally allocated to a hood, is in proportion to the average body surface area increase. A jacket covers approximately 48% of your body surface. A hood covers approximately 7% of your body surface area. 7/48 = 15% anticipated increase in the amount of uniform coverage down oz by adding a hood. The fill values you quoted are approximately 28% higher for the MH Sub Zero hooded jacket. This infers that additional insulation was also added to the jacket. In other words, 300.15g of down, not 364g is required to add a hood with equal warmth to the rest of the jacket.

The MH Phantom uses approximately 9 oz of 800 fill and so it will be warmer than the MH Sub Zero jacket using 261 g (9.2 oz) of 650 fill.

200g Primaloft One insulation equals 6 oz/yd2 and 1” of loft. The theoretical clo value, based on the insulation manufacturer’s spec would be 5.040 clo. The laboratory tests I conducted on two different manufactures garments, using this insulation, yielded about 2.52 clo. By contrast, the MH Sub Zero tested 4.521.

Your reading about people using 200g Primaloft One jackets in 0F weather means nothing unless you at least know there average MET rate for the rating period in addition to the their core temperatures before and after the rating period. For example this winter I spent a full day out in -30F wind chill temps wearing only a Power Stretch hoody and hooded wind shirt and was comfortable. Although the preceding sentence is true it is of no value to your ability to gauge the warmth of a Power Stretch hoody. Only if you knew I was that my average MET rate for the day was 7 could you approximate the relative warmth of what I was wearing.

Richard,
Thanks for your very insightful response. Good info.

QUESTIONS:

Does "laminating" (instead of quilting) Primaloft Sport substantially improve the warmth, waterproofness and longevity of this material (per a mfgrs. statements)?…

BTW, isn't 650 x 261g fill (MH SubZero) warmer than 800 x 197g (MH Phantom) (MH quoted me 7 ounces instead of ~9oz.)?…

I am not sure there is much advantage in laminating Sport. Sport has minimal quilting requirement so seam stabilization may be sufficient depending on the pattern. Seam will be there even in a garment made of laminated sport. Difference in warmth will be minimal.

Lamination is done to liner.. so waterproofness will depend on shell fabric, zippers and whether it is seam sealed.

Longevity? not sure. synthetic insulation do not have much of a life anyways.

Richard, did you get my PM?

David

You are correct on the fill amount for the Phantom. I was going by memeory. I looked at my files this morning and the Phantom was listed at 197 g or 6.948 oz for size L.