The best clothing combinations for backpacking or hiking?

[Joshua Mitchell]

If you take a look at the following exchanges, specifically my questions, it should help.

http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=8931&startat=20

Realize that and out put of 1000 (kilocalories per day) = 48-49 watts. (1 820 (kilocalories per day) = 88.1351852 watts)

You're 'average' male has a resting wattage of 80.1 W. This is what Richards graph would likely have been based on. Whatever YOUR BMR winds up being, you can more or less correct the amount of Clo required by inverting the relationship. (aka people with higher BMRs require less Clo to stay comfortably warm)

Of course, this doesn't get into personal preference of what is considered 'comfortable'. These calcs should be used as a starting point.

[Jaiden .]

OK, I think I've got the W/m2 now.

I found:
1 kilocalorie / hr = 1.16222222 watts

So my kcal/day BMR of 1820 divided by 24 hours, times the above gives me 88 and my wife 62. This divided by m^2 gives us 45.2 and 42.75 respectively. Not much difference, but I can vouch for a huge difference in our relative comfort levels.

[John S.]

Touche' mon frere (?sp). Just trying to rile you CLOers up. Don't pay me no attention. I'll be over at the backpacker.com forums if you need me.

John

[Jon Rhoderick]

OK
Sooo I've done know how to do the calculations for the BMR now, but how do you do percentage of surface area? I saw a little of that lab report, but I don't really wanna read through all of it if someone could do the equation.

any help?

PS, we should get a copper mannequin for BPLs birthday or for Festavus.

[Jaiden .]

Well, I put all the measurements into a spreadsheet, adding left/right sides and then added them up for the total surface area. Then for each body part, I did a simple formula which divided the number for each part by the total. this gives me a % of the total, which I'm assuming is relatively standard, even if the actual area isn't. Then I add up the parts that make up a garment.

Here's the table I got, with some examples of items. I guessed that a hoodie with thumb holes covers 60% of the head (not the face) and 40% of the hands (not the fingers).

body part % area m2 % item %
legs 0.1771 0.120157406 pants 0.462107334
feet 0.0883 0.059909085 jacket 0.34968451
thighs 0.33 0.223895787 hoodie 0.415930524
crotch 0.174 0.118054142 vest 0.282515774
head 0.11 0.074631929
hands 0.0791 0.053667142
arms 0.099 0.067168736
shoulders0.1514 0.102720673
chest 0.138 0.093629147
back 0.127 0.086165954
0
0
0
0
0
0
1.4739 1

[Jon Rhoderick]

so is that the mannequin's measurements or yours? I suppose there would be large differences for each person, especially between the genders in the chest region.

[Jaiden .]

The mannequin's… I have better things to do than measure my surface area to 4 decimal places. I figure that though the area itself changes, the proportions probably don't very much. Besides, it doesn't look like she has much up top to skew the chest percentage.

[William Webber]

Basically you seem to be saying you don't need a lot of heavy clothing to keep warm! An R1 and Houdini are pretty minimal. Your chart is supported by my own experience in summer hiking to the High Sierra Camps in Yosemite (near Tuolumne), although I have some variations noted below.

Here are my personal variations:

I never hike in shorts and short sleeves – too much sun exposure for my taste. I use a sun umbrella from Go-Lite to keep the sun off me. This also doubles up as rain protection in a summer shower. I wear a long sleeve, silkweight Patagonia crew neck tee shirt (I think they call this Capilene 1 now). For pants I wear long pants, light Supplex nylon pants from Ex Officio, but hemmed high, about the length of knickers – to just cover the tops of my socks. This lets the air circulate over my legs. The long sleeve tee shirt is theoretically hotter than a short sleeve, but with the umbrella most of the heat is kept off me so it balances out. The "hot spot" I have is under the pack, but I try to use a Breeze from Go Lite and just shift it around to let one half or the other of my back dry out. I've been tempted to try one of the vent panel backpacks, but they are pricey.

The preceding outfit is plenty to keep me warm; on a summer high sierra hike, the only time I need to add anything is heading early out of camp, at dawn, when a nylon windshirt helps – I like the old, discontinued Wild Things Gear nylon windshirt, it isn't too hot.

If temperatures have been trending cooler, I will wear a zip neck, lightweight (Capilene 2, nowadays) long sleeve as my base layer, and back it up with either a Capilene short sleeve, crew neck tee shirt worn over in lieu of a vest, or a tank top Capilene (they have these from time to time). Finally, the windshirt. As you noted, it doesn't take much to increment the comfort level back up. If I am in an urban environment and its cold, each incremental layer has to be a lot thicker, but when I am hiking the incremental levels are a lot thinner – and the "warmth" generated by the higher metabolic level triggered by hiking tends to carry through after I reach camp, at leas for a while.

I end up carrying a second windshirt, a Houdini, as my rain gear. I try not to wear this unless it is raining, to preserve its water repellency. It isn't perfectly waterproof, but I follow the theory that while hiking I'll just be evaporating off any wet through anyway. This approach might not work in the fall in New England, but it's been fine so far at Yosemite.

I end up carrying a THIRD windshirt (good thing these are light!) as a "vapor barrier" for sleeping. I use one of the original Patagonia Dragonflys, notorious for their poor breathing, which in this context is a big help. It has a hood, and I wear this over my head, with or without a watch cap. I find the Go Lite Snow Cap a little hot in summer.

The one part of the equation I haven't nailed yet, is what to wear to bed to "up" the temperature rating of my quilt. I like to wear enough go to sleep with the quilt just over my legs, and then adjust the quilt up higher as it cools off during the night.

Quite frankly, the R1 hoody sounds very appealing as the "missing link" in my kit. It would obviate the need for a watch cap and Snow Cap; it looks good at the dinner table; and I could wear it under my windshirt around camp in a drizzle, or over the windshirt when sleeping (for the vapor barrier effect). So far I have been experimenting with synthetic fill vests and pullovers, and with heavier Polarguard like the Body Rug from Patagonia (a very high loft, equivalent I suspect to 300 but lighter in weight).

The only conclusion I have come to over five seasons of hiking, is that you need a different "kit" and approach for "active" trips and "take it easy" trips.

If you are going to be very active, with little time spent idling around camp outside of a sleeping bag, then every item of clothing needs to be much thinner. Silkweight for baselayer, R1 for insulation, a Micropuff Pullover for extreme insulation.

If you are going to go to Camp Curry in the dead of winter and rent an unheated tent cabin – as I have done – every item of clothing needs to be MUCH thicker – mid-weight zip neck tee, R2, down parka or thick synthetic parka. Otherwise the cold weather coupled with the inactivity will gradually suck the heat out of you and leave you miserable.

In any setting, though, layers seem infinitely better than just wearing a tee shirt for the sunny hike and carrying a thick down parka for camp, which is the main point of the post, I suspect.

Still, I like the elegant simplicity – lighweight baselayer, midweight (R1) hoody, windshirt. That's a slick analysis.

[Phil Stetz]

Richard – This is great work. I've been following the thread for a number of days now and I've learned a lot about the details and science of staying warm. I have a few comments / questions:

1) Would you consider publishing the actual spreadsheet? Or re-posting a larger graph w/ a different background? I'm having a hard time reading some of the details.

2) What about wind chill? Would this factor into any of the equations? Or do we assume this is not a factor due to the wind shirt?

3) Gloves? Or do they only contribute to 'comfort' level since they are only covering extremities and not insulating the core? Same for a fleece hat. I suspect this would contribute more to warmth than gloves due to the blood vessels in that area. Or do we assume this is covered by the hood?

Thanks again for the great post. You saved me a lot of discomfort this weekend! I generally consider myself to be warm natured, but now I will bring some extra clothes for insurance.

[Jon Rhoderick]

another two to add to that list of questions

4) what about lower legs, I dont think youd be very warm with a down jacket and supplex pants?

5) is the down jacket's loft single layer or double?

This thread is really starting to grow on me.

[Richard Nisley]

I will go through the posts and try and answer the outstanding questions in a subsequent post. But first, I wanted to address the common high level abstraction question. In other words, FEED A MAN A FISH, FEED HIM FOR A DAY. TEACH A MAN TO FISH, FEED HIM FOR LIFE.

The most practical way for a backpacker to determine the dry Iclu clo value for an ensemble is to measure the thickness of each garment component; multiply the thickness by 4 clo; and then multiply by the percentage of an average body it covers. Add these individual garment calculations together to calculate the Icl clo for your clothing ensemble. For high loft garments, the materials actual clo per inch can be used for a little higher accuracy but is not normally necessary for base layer garments.

The simplest thickness measurement is done by placing the garment on a table; placing one wooden ruler on top of the garment; measuring the double thickness with the other wooden ruler; and then dividing this value by 2 to determine the single fabric thickness.

The key standard mannequin values are 80% BSA for a one piece suit; 54.5% BSA for a hoody; 48% BSA for a jacket; 36% BSA for a vest; 22% BSA for a PFD or singlet; 7% BSA for shoes; 7% for complete head coverage; and 5% BSA for gloves.

Malden Mills makes 25 different variants of Polartec 200 fabrics. Malden Mills specs range from 13.5 oz per liner yard to 20.5 for the different fabrics. Compounding this variance is that each manufacturer can use different face fabrics and combinations of fleece types in the construction of a single garment. The overall thickness is critical in determining the thermal resistance of a garment.

The only completely accurate way to measure a garment’s dry Iclu clo value is on a thermal manikin in a lab. Each manufactures garments would have to be tested because each of the various combination of fleece and face fabrics used. A single garment test costs on the average of $600. Even if a manufacturer goes to the expense of measuring a garment’s Iclu clo, they rarely release that information. The manufacturers marketing department prefers to be differentiated on more defensible features such as brand name, colors, or styles. The North Face lists in their “Fleeces and Softshell” products 30 unique models for men and 33 for women. Every one of these garments would have unique clo values as would the range from every other manufacturer in the world.

The ISO 9920 international standard’s data base is excellent for conventional street clothes but is worthless for technical clothing used for backpacking. For example, the ISO 9920 standard lists the Iclu clo value for a down jacket as .55 Iclu clo. Even the 650 fill down jackets used by the Air Forces averages about 1.05” thick and are manikin tested at 2.2 Iclu clo. The 1 ½ thick 800 fill jackets are the standard for cold weather backpacking. The only way you will get the Iclu clo for the ensemble in your closest is by calculating it yourself.

[Jim Sweeney]

Here's a website that lists the definition of ICL (CL0), many other terms, and gives a program for computing required insulation (though this might be the site that Richard considers not that useful for backpacking):

http://wwwold.eat.lth.se/Forskning/Termisk/Termisk_HP/Klimatfiler/IREQ2002alfa.htm

I think this is an extraordinarily valuable thread, and many thanks to Richard, though I confess I'm not at all up to speed.

[Richard Nisley]

Joshua M. –

Q1: IB Nomad clo value?
A The short answer is the Ibex Shak is 390 g/m2 and measured .080 loft. The IB Nomad fabric weight is 320 g/m2 and measured .080”. 320 / 390 * .080” = .066” or a Iclu clo value that is 18% less than the Shak, which is the same as the R1 hoody.

The long answer is that determining the clo value of a stretchy technical base layer such as Merino wool, Power Dry, or Power Stretch is a little more complicated than other conventional insulation pieces like jackets and vests. For the R1 Hoody, the applicable ISO 9920 formula is Iclu = .43 X 10-2Acov + 1.4 Hfab x Acov which would yield a clo of .4. Acov is the body area percentage as a whole number and Hfab is the thickness in meters. When older style base layers, like cotton or wool, are tested on manikins, they closely match the formula. If you want to be conservative, just use this formula for your base layer.

I used an Iclu clo value for the R1 Hoody of .539 in my chart. I did this because my testing showed that the R1 hoody’s stretchy material and unique cut resulted in no fabric compression and an optimal uniform air gap at the skin. Also the uniquely tailored balaclava style hood was far better tailored and warmer around the neck and head than any other style I tested. Manikin testing doesn’t reflect the fact that the vessels in the neck and head don’t vasoconstrict like the rest of the body. So real world testing would be higher than the manikin test showed.

I kludged this formula for use in my chart to represent what I experienced.

So if your IB Nomad fits every part of your body, including your neck and head perfectly, then adjusting from the high .536 Iclu clo value of the R1 Hoody makes sense. If not, use the more conservative ISO formula I provided above.

My testing showed that the Smartwool hoody’s hood and neck area had large billowing air gaps and so the standard ISO formula is applicable. My Ibex Shak was designed similar to the R1 for similar warmth. My Ragged Mountain hoody has a bad fitting neck area. The air gap fit is only an issue in the base layer. Having the rest of your layers fit with gaps doesn’t generally reduce the thermal comfort level.

The ISO formula above generally works well for base layers and conventional street clothing. For high loft insulation layers, the formula I previously provided works best (4 clo per inch x loft in inches x BSA%). As I mentioned previously, the accuracy is improved if you know the actual clo per inch for the material type and use this value.

Q2:…should one adjust these values if it's likely to be wet?

A2: For Merino wool and Polarguard, you should build in a safety tolerance. For polypropylene or polyester base layers and Primaloft insulation it isn’t necessary.

[Richard Nisley]

Johnathon R –

Q: Where are the clo values coming from?
A: For street clothes, the ISO 9920 data base. For technical base layers, the ISO 9920 formula for determining the clo value from the body surface area % (BSA%). For exceptionally engineered base layers such as the R1 Hoody, my testing showed that they were warmer than the ISO formula would indicate and so I created an additional formula. It should be noted that the ISO formula shows a .080 base layer hoody should provide .4 clo. The manikin tests ran by the Armed services on their clothing showed that there best base layer top tested .4 clo without a hood. So I don't think it is too much of a stretch for me to estimate the R1 hoody at .539.

After you have figured it out for your chosen clothing ensemble, please share with us how the numbers come out and how they compare with your real world experience.

[Richard Nisley]

Matt F. –

I agree with you that 99.9% of hikers don't know the clo values of their gear and don't care. I would love to understand why they don't care. I suspect that it is because they believe that there is no EASY way to get the answer. What are your suggestions for how to better present this type of information so that more than .1% would find it beneficial?

[Richard Nisley]

Bill –

Clo is the insulation provided. Clo is normally used for clothing insulation because it is relatively easy for people to understand that 1 clo is the warmth provided by a mens business suit.

1 MET is the amount of calories you are burning and consequently the amount of heat you are generating when you are in a prone rest position. All other activities are represented as multiples of this calorie expenditure / heat expenditure. You are only comfortable when the heat generated is the heat lost.

Thanks for helping me understand that I should have started by defining these terms.

[john flanagan]

Richard – I can tell you why I don't pay much attention to this level of detail, especially with regards to clothing…

Primarily, there is a limit to how much obsessing about gear that I want to do. The CLO value of base layers as an example goes beyond that threshold. It's the same reason that I have no aspiration to be super duper uber light – I don't have the patience for it.

I want a flexible clothing system that meets a wide range of conditions with a reasonably small gear closet. My (possible mis-)perception is that you take a more honed approach and (my guess is)have invested more to create options that meet more specific environmental conditions.

You ask the engineering question – what is the optimal solution? I ask – what do I have that will get 'er done? You conclude that hoody plus windshirt is an optimal solution for hiking in dry cool to cold weather. I concluded a long while ago that a baselayer and windshirt works great most of the time when it's chilly. Not having a hoody and owning a few wool caps – I conclude "good enough". Different process – similar solution.

It's not that I don't learn from you and others who plan in greater detail… I just don't invest as much in finding the "best" solution.

[Richard Nisley]

Jaiden – MET values are available at for almost all activities. Just pick a number from this data base

MET Database

I answered your clo calculation question in a prior post answering another person with a similar question.

The average clo per inch for insulations is 4. 800+ down fill is 6.562 clo per inch if it is fully fluffed. You need to use clo/inch and not clo/oz for the Iclu clo calculation. If you don't know what the actual clo per inch is, just use the average which is 4 (3.906 to be more exact).

[Joshua Mitchell]

Richard,

Thanks for the reply, I'm pretty sure I follow it, but if you'd stick with me I want to paraphrase it back to you to be sure I understand.

1) From a purely material point of view, 320 g/m2 Merino is approximately equal to R1 material when it comes to material Iclu clo calculations.
1 alt) An alternate reading of your sentence would be that 390 g/m2 = R1 (aka Shak = R1)… so from a materials point of view 320 g/m2 ~ 88% R1

2) ISO specifies a standard hoody BSA% for use in the clo calculations. These calculations Smartwool hoody conforms to this pretty well, as the SW Hoody fits much like a standard ISO Hoody. However because of superior design the Shak and R1 Hoody outperform ISO Hoody predictions (one could consider this to be an increase in effective BSA%).

3)If the Nomad fits better / closer than a standard street hoody, treating it as a Smartwool hoody would be 'conservative'. If it's more loose-fitting around the neck (as is the SW Hoody), treating it as a SW would be 'equivalent'.
3 note) By my recollection the SW Hoody is ~ 320 g/m as well. If this is not the case (aka the nomad fabric is lighter than the SW Hoody fabric), then I would replace 'conservative' with 'equivalent' and 'equivalent' with 'optimistic'.

Of note using the ISO Formula the SW Hoody comes to about a 0.50 Iclu?
Also, so clarifications on the ISO Hoody Forumla:
A) Which is the correct placement of parenthesis.
Iclu = (.43 X 10)-2Acov + (1.4 Hfab x Acov)
Iclu = .43 X (10-2Acov) + (1.4 Hfab x Acov)
B) "Acov is the body area percentage as a whole number and Hfab is the thickness in meters" what you mean is that for Acov, is should use MY body's total surface area (found from the BMI calculator page) x the ISO '54.5% BSA for a hoody', the Hfab I can measure with rulers.

EDIT – I just realized that those numbers presume a certain body size (total surface area) do they not? Though of course, if I simply wanted to estimate it, as long as I adjust the Clo needed for my BMR compared to the average male BMR thatn I'll have a pretty good 'starting point' for estimating my ensemble needs.

[John S.]

Richard, anybody that knows me..knows I am full of bull much of the time and joke around alot. Some of my posts are of the brutal honesty type that do not necessarily go over well with others.

I honestly had not heard of clo until you had mentioned it in the past. I guess I'm like Jack Flanagan who doesn't worry much about that part. Not that it doesn't have meaning, and it does, because it allows someone to calculate how much insulation the gear provides. So, it is important.

Why do they not care? Maybe only because those numbers are not provided easily up front on purchase for the average person to educate themselves on the meaning so they can compare the values with other gear they own or are shopping for.

As for suggestions on how to better present the information? I don't see how anybody could present it better than you have. I do appreciate when someone like you takes an interest in an area that many do not understand. Keep up the educating posts.

[Jaiden .]

I'm still really lost here, as none of my calculations ever come out to match yours. I'm sure I'm misunderstanding something. It seems that the more I dig into this, the harder it becomes. I hope you don't take any offense if I've misquoted something.

As I own a Shak, I've tried to duplicate your numbers for that.

Attempt 1)
Per an older post, wool is clo of .08 per oz
.08 clo/oz* 17.5oz *.545 = .763
(.545= 54.5% body coverage in a hoodie, 17.5 being my measured weight on a crappy and probably incorrect scale)
This one is wrong, you already told me not to use this way

Attempt 2)
"If you don't know what the actual clo per inch is, just use the average which is 4 (3.906 to be more exact)."
"The short answer is the Ibex Shak is 390 g/m2 and measured .080 loft"

.080 * 4 *.545 = .174… much lower than the numbers quoted for the shak elsewhere.

Attempt 3)
"Iclu = .43 X (10-2Acov) + (1.4 Hfab x Acov)
Acov is the body area percentage as a whole number and Hfab is the thickness in meters"

Iclu = .43 * (10-2(.545)) + (1.4 (.080*.0.0254) x (.545))
this gives 3.83, and a negative value if I express Acov as a "whole number" (54) instead of a decimal. Both clearly very wrong.

I'm sorry I'm so dense on this matter, but it seems that the information on the subject is scattered in many places and is sometimes contradictory. (I'm not putting this on you, I mean the ISO, EN, etc.)

Perhaps we can add a column to the gear guide for the actual clo of the item? At least a list of common items all in one place would be nice. I think a lot of us have identical or similar gear.

Thanks again for all your efforts in attempting to educate my concrete filled head.

[Phil Stetz]

I would like to add on to Jaiden's suggestion. Repackaging all the information that is available in this post (and a few related ones) would go a long way in making this topic clearer. I think Richard has done an outstanding job in presenting the information, but I think some of the clarity has been lost due to it being jumbled around in the forum posts. I think this would be an excellent topic for an article.

[Steve .]

Would be nice if the clarified version would turn into an article for general consumption.

[Aaron Sorensen]

It's weird how all of Richard's charts go in strait lines, (meaning they should be easy to understand)???

I wonder how many mets I'm burning while you're trying to figure out your clothing and met rate to see what you need for a certain temperature and then trying to figure out what articles I need to put on when I stop thinking about it, aahh, I'm getting cold.

[Jon Rhoderick]

Coming soon

THE COMPLETE IDIOTS GUIDE TO CLO!!!

[Author]

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