I created this chart to graphically demonstrate why I believe a lightweight hoody and a windshirt is the optimal clothing combination for most backpacking or hiking. For backpacking, this combination allows an effective 46F on-the-fly thermal comfort adjustment in the general range of 46F to 0F. For hiking, this combination allows an effective on-the-fly 25F thermal comfort adjustment in the general range of 69F to 44F.

Chart Label Descriptions:
Hot Ensemble – Hot weather ensemble consisting of briefs, light shorts, short sleeve Capilene crew shirt, socks, and trail runners (Icl clo = .30)

Mid Ensemble – Middle temperate ensemble consisting of briefs, long Supplex nylon pants, long sleeve Capilene crew shirt, socks, and trail runners (Icl clo = .60)

R1Mid – The Mid Ensemble with the long sleeve Capilene crew shirt exchanged for the R1 Hoody and a wind shirt. The R1 hoody can achieve the same clo as the Capilene long sleeve crew when the sleeves are pushed up, and the zip is at the lowest point (Icl clo = .60 – 1.10)

R1Mid+Vest – The R1Mid ensemble with the addition of a Polarguard Delta Micropuff vest (Icl clo = 1.80)

R1Mid+Pull - The R1Mid ensemble with the addition of a Polarguard Delta Micropuff pullover (Icl clo = 2.02)

R1Mid+P+V - The R1Mid ensemble with the addition of a Polarguard Delta Micropuff pullover and vest (Icl clo = 2.68)

R1Mid+DJ - The R1Mid ensemble with the addition of the New Balance Fugu down jacket which has 1.5” loft (Icl clo = 4.29)

3 Season SB – The REI Sub Kilo, which is a representative 3 season sleeping bag (Icl clo = 8.00)


The backpack MET is a range that varies between 7 and 9.

The light area between the Mid Ensemble’s MET line and the R1Mid’s ensemble MET line represents the dynamic adjustability afforded by the stretch fabric, the hand warmer function, and the deep neck vent.

High loft insulating options are only used for non backpacking or hiking functions.

The hot weather ensemble is suggested for backpacking in effective temperatures greater than about 45F and hiking in effective temperature greater than about 78F.

Substitution with other brands of hooded windshirts will not effect the clothing ensemble Icl value

The dashed horizontal clothing ensemble clo lines can be adjusted for different hoodys using the following adjustment factors:

Ibex Shak (0 clo)
Smartwool hoody (-.035 clo)
Ragged Mountain or Wild Things Polartech Powerstrecth (+.050 clo)
Any brand Polartec 100 (+.068 clo)
Any brand Polartec 200 (+.115 clo)
Any brand Polartec 300 (+.170 clo)

If a clothing ensemble is worn in a sleeping bag, the sleeping bag's temperature rating is increased by the ensemble's Icl clo value. For example, wearing the R1Mid+Vest ensemble in a 3 season bag with a clo value of 7.32 will increase it to 9.12 yielding a 17F improvement best case. This assumes enough space in the bag such that the clothing ensemble loft is not compromised.

Edited by richard295 on 09/02/2007 22:10:14 MDT.

Any chance you could do this in celsius/metric ergs.[just kidding]
This is a very nice piece of work which I've cut and pasted and blown up a bit.
We really need people like you a lot more then we need people like me explaining to the newbies, I'm way too much from the let's through some clothes on and get going/what do you mean your cold school of hiking. Again, nicely thought out.

Thanks for putting this together Rich. You state that the best combo is the r1 hoody and a windshirt. However, your R1Mid+Vest or R1Mid+Pull, etc do not mention a windshirt. Is that thought that if it's windy, you simply complement the R1 "package" with a wind shirt?

I'm thinking this is what I'm going to try for my next Fall trip where temps are going to be 70-80s during the day and then dipping into 40-50's at night.

- Capilene 1 Tshirt
- R1 Hoody
- Micropuff vest
- Houdini wind shirt

Your thoughts?

Frank - The windshirt is present in all configurations starting with the R1Mid... thanks for pointing out the omission. I will edit the original post for the R1Mid description to add the words "and a wind shirt".

Your clothing list looks ideally suited for your trip.

Edited by richard295 on 09/02/2007 15:58:09 MDT.

Can you please provide two URLs, one for your chosen R1 Hoody (which I have not heard of before) and the Windshirt you used?

Thanks!

The R1 hoody is made by Patagonia. There was an original version with an offset zip, and then the present one which is at this link... http://tinyurl.com/2o9uzr

I used a Patagonia Houdini windshirt and a Patagonia R1 hoody for my analysis but, the brand isn't critical to the thermal performance concepts. The Patagonia URL is Patagonia

There are other combinations of garments which will provide comparable thermal performance flexibility. For example, the Montane Litespeed windshirt, in combination with the Ibex Shak wool hoody, would be about the same.

Edited by richard295 on 09/02/2007 19:04:22 MDT.

Great graph and well thought out clothing system!

I would note that some people run hotter or colder depending on their personal physiology. The graph look spot on for the people I know who run on the cool side (mostly california natives).

Provided I have had adaquate food and water the clo indicated on this chart would have me overheating. I use very similar clothing system, though mine is roughly 1/2 the clo of Richard's, but I wear mine in similar conditions / activity levels.

My substitutes are

R1 Hoody --> LS Featherweight PowerDry Zip Neck
Houdini = Houdini
Micropuff Vest --> Thermawrap Vest + PolarBuff
Micropuff Pullover --> Thermawrap Jacket + GoLite SnowCap

For example, at sitting / talking activity level I am good with just my featherweight shirt and a windshirt to around 55F. If I add a vest and a hat I am happy to around 30F.

Richard,
Sorry, I don't understand your graph, but I want to.. Does it show the temperature range for comfort at some constant clo? Because it seems to have lines of constant MET, not clo.

It plots temp vs clo, and there is a line of with constant slope for each clothing combination.. This seems to show the clothing is suitable for some constant MET (eg 1.5) at the combinations of temp and clo. But the MET line tracks along a range of clo values, which should be constant, right?
Shouldn't each clothing combination line be at constant clo and show the MET to be comfortably warm at each Temp?

I know.. there are no stupid questions, only stupid people, I hope I phrased my question ok.

Mark - I alway appreciate your input! I frequently reference your Web site for information and also point others to it.

You are representative of the younger and/or more fit individuals will need less insulation than the theorectical average used by all International Standards. I designed my chart for the International Standard male. This guy is 154.3 lb, 68.9" tall, 30 years old, a body surface area of 19.86 ft2, and a BMR W/m2 of 44.5. This is the same standard that most of the 50 thermal dummies in the world use for all thermal testing and standards work. For those people wanting more customization in the values, they can adjust them for their unique BMR.

Based on some of the questions that preceeded yours, I added some additional information to end of my original chart explanation prior to this post. Hopefully that information and this post will make this topic easier for people to understand.

The graphs shows two trends:

1) That the higher the level of activity (MET) the less insulation is required

2) The the lower the temperature, the more insulation is required.

I believe the way to use the graph is select a temp (say the low temp you expect to see on a trip). This selects the X axis. Next select an activity level (say sitting/talking). Find where the line for activity crosses your selected temp. That gives you the Y axis position which would suggest according to equations Richard has been working with how much insulation you need. The right side lists CLO. The left side is the clothing combinations that Richard uses to achieve the CLO values.

Hmmm... I wish was was a younger / fitter individual than the theoretical average... but I am more than 15 years older and 25lbs heavier. Actually the younger / fitter folks I backpack with seem to need more insulation that I do. Perhaps the additional body fat makes it easier for me to keep warm. Seems to work for the Inuit.

Brett - Question 1) Does it show the temperature range for comfort at some constant clo?

Answer 1. No. Temperature and METs are the two input variables, the clo value is the dependent output variable. Each yellow line uses a constant MET value (shown on the line's label) in combination with the temperature variable to generate the yellow line plot.

Question 2) ...the MET line tracks along a range of clo values, which should be a constant, right?

Answer 2) No. The clo values are the output values for the input values of MET and temperature. Each dashed red line lists the clo value for a representative clothing ensemble. The calculations for the dashed red lines are an independent set of calculations.

In summary the charts yellow lines shows the temperature dependent clo required for each of the 7 levels of exertion (METs) typical of backpacking trip. The red dotted lines show the clo provided by common backpacking clothing ensembles. The intersections of these lines show you what activity and what temperature the clothing is adequate for. You need to have a clothing ensemble clo value that is equal to or higher than what is required for a given MET level and temperature.

It is easy to make things look complicated; the difficult part is to explain things in the clearest and simplest terms. Your questions show me that I need to do a better job of communicating.

Edited by richard295 on 09/02/2007 22:01:55 MDT.

So I can enter the chart with my forcast day and night lows and get the required clo's as output; (at the METs for day hiking and night resting, etc..) Got it. This chart is another keeper.

Richard,

Using an IB Nomad, I'm getting a clo value of 9.4379279 (320 g/m2 converted to oz/yd2) * .08 = 0.755034232, which would put it roughly on par with the Smartwool Hoody, correct (aka a correction factor of -0.35 clo below the R1)?

Also, something I haven't heard asked before, but other than the obvious need for staying dry as much as possible, should one adjust these values if it's likely to be wet (if nothing else, under most 'wet' conditions, you'll have some wetting due to condensation)? Aka, should one allow for a bit of extra clo to account for any clo reduction from the wetter weather?

Edited by jdmitch on 09/03/2007 10:59:28 MDT.

Where is the base data (clo values) for all these clothing types coming from? I was considering asking a really obnoxious question for everything I own, but I hope I could figure it all out on my own.

99.9% of hikers don't know the clo values of their gear and don't care. Just bring clothing to stay warm and dry and you should make it through your trip.

Matt, your post makes sense if we were on the backpacker.com forums.

I'd like to understand what the chart is saying but I don't know what a ClO or a MET is. I know what gear works for me to roughly what temp. range.

For instance. I can start out at a trailhead in mid 70 deg's with a s/s wool t-shirt & long softshell pants. By the time I'm sitting on a summit, it can be 40 deg. w/ a 40 kt wind and I'm still ok at long as I have a Houdini. If I plan on lingering in a windy spot for a while, I'll need a light hat & gloves. Any colder and I'll put on my Cocoon pullover & possibly a shell.

While I didn't need to know what a CLO or a MET was to figure that out, I'd still be interested in learning. Any help would be appreciated.

Richard, count me in as another who devours your posts eagerly. I'm a total newbie and am enjoying your "classes." Please don't anyone else rely in the information I give in an effort to ask my questions.

I understand this graph, but I have a few questions about the calculations needed to create one of my own.

First, in calculating MET (based on the url you gave out earlier), I get a BMR of 1820 for me and 1281 for my wife. I divided by 24 (hours) which gave me 42.1 and 35.6 respectively. If I'm correct, this means that neither of us are as "warm" as the average person. This doesn't surprise me for her (I swear she's a reptile), but I'm always warm, so it makes me suspect that I did something wrong. When I do get the right value, does this just become a linear scaling factor for the graphs you post? In other words, how do I know how much more clo my wife needs than the average person?

Second, I am a little confused at trying to calculate the clo of garments that I own. Since I have some of the same items you do, I should be able to get things to line up better than I do. Here's how I'm calculating clo for an item:

Take the item weight, subtract noninsulating weight, or otherwise calculate the fill weight. Multiply this insulating weight by the clo/oz factor from your other post. Multiply this value by the percentage of the body that is covered by the item. Please let me know if this is wrong.

I do find different numbers from this url http://repositories.cdlib.org/cgi/viewcontent.cgi?article=1046&context=cedr/cbe than I see in your posts for the percentage covered.
I get:
body part area m2 %
legs 0.1771 0.120157406
feet 0.0883 0.059909085
thighs 0.33 0.223895787
crotch 0.174 0.118054142
head 0.11 0.074631929
hands 0.0791 0.053667142
arms 0.099 0.067168736
shoulders 0.1514 0.102720673
chest 0.138 0.093629147
back 0.127 0.086165954

Which when I figure a hoodie covers 60% of the head and 40% of the hands gives:
item %
pants 0.462107334
jacket 0.34968451
hoodie 0.415930524

These aren't big differences, but I thought I'd share my calculations.

Third, I recently bought a Nuptse vest for my wife. http://www.altrec.com/shop/detail/13916/
which I'm guessing is around 14 oz of 700 fill down. I see that you have 850 fill listed in your table of clo/oz, but not the lowly 700 fill, and I can't seem to find that information anywhere. Do you have it?

For those that missed it, here's the table I'm using, courtesy of Richard:
clo/oz
Cotton 0.04
Merino wool 0.08
Polartec 100,200, 300 0.16
Polarguard 3D 0.63
Exceloft 0.68
Polarguard Delta 0.68
Climashield HL 0.68
Down (550 fill) 0.7
Primaloft Sport 0.74
Climashield Combat 0.79
Climashield XP 0.82
Primaloft One 0.84
Down (850+ fill) 2.53