Do these CLO values look right to you?

Yeah, that makes no sense. It is a non-specific down jacket and parka so not very useful regardless, but a .55 clo down jacket would have, like, no down in it : ) They did seem to correctly convert between clo and m2K/W though

engineeringtoolbox has some other tables that seem pretty good

The wikipedia table is similar, but has fewer items

http://en.wikipedia.org/wiki/Clothing_insulation

Confusingly, Wikipedia lists the values in the table as being:

Icl (clo)

…which I read as both Intrinsic, and Total (for garment) CLO.

As those two measurements are quite different, I find this odd. I thought that Iclo didn't factor the garment's coverage (to use it, you'd have to assume a human was completely wrapped in said insulator), and CLO did. As I understand it, you should be able to add all the separate CLOs in your ensemble to determine your overall/total CLO.

Notice also that Wikipedia considers a CLO of 3 (what many of us would consider a typical down jacket by itself) a "polar equipment" outfit?

My point being, I'm getting wildly different values and ranges for garments from different sources.

I agree, lots of confusing info about insulation

They don't define the term Icl(clo), but maybe it's insulation of clothing in units of clo, not intrinsic clo

I think the terms clo and intrinsic clo are sometimes intermingled. I think clo = intrinsic clo * amount of body area covered, but a lot of times people just use the term clo when, technically, they should use the term intrinsic clo. In a way, it doesn't matter, because if you're selecting a jacket with a specific intrinsic clo, you're also going to be wearing pants and hat of similar intrinsic clo.

If you take Richard's chart http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/9378/index.html, for sleeping, a clo of 3 is good down to about 62 F – not polar. But, if you're walking at 3 MPH level (MET = 3.3), you're good down to maybe -30 F – off the chart but just eyeballing it – that could be considered polar.

Delmar,

iClo is the intrinsic measurement of the insulation only at its areal density. Clo and iClo measurements are the same for sleeping bags because the insulation covers ~100% of a person's body surface area (BSA). But for other garments with a thermal dummy measured Clo value of 1, that insulation's iClo will be ~ as follows for each garment type made from the same insulation:

Vest = 1/.36 = 2.77 iClo
Jacket = 1/.48 = 2.08 iClo
Parka = 1/.52 = 1.92 iClo

Thanks for the help. I really do need to figure this out. I'm helping a friend prepare for a singlehanded circumnavigation of the Americas. Last trip (in the Pacific) he was miserably cold, days on end, as he sailed toward Alaska — he thought he'd packed plenty of insulation, but apparently did not (and he came from the South Pacific which made everything seem colder than it was, by contrast).

He wants to methodically select and carry sufficient clothing and sleeping bags, yet, like all of us, his space is limited (a sailboat isn't so big once you provision it for several months of sailing). I've been telling him that understanding CLO is the way to do this (semi-)scientifically, or at least, methodically. Yet every time I try to explain CLO to him, I get tripped up by things such as a down jacket being either .5 or maybe it's 3.5, who knows, no explanation for the difference.

For a user of the system, Iclo is kinda academic, and only useful to compute CLO, which is what you want and need to make estimates.

I have Richard's posts to thank for what little I understand of CLO, (thanks Richard). What I need is a "CLO for Dummies," I guess.

So — no resolution on the tables at Wiki and Toolbox, vs the numbers we see here at BPL? Choices:

– Discard all the numbers in the tables, they're wrong. Hunt through all the BPL posts and use those.
– There's a misunderstanding or conflation of what the numbers in the columns are; eg, Iclo vs CLO vs whatever
– The numbers in the tables are close to correct, on average; the numbers we get from manufacturers are vastly inflated;
– The numbers in the tables are close to correct, on average; there are a few errors for heavier clothing;
– Other?

> I think clo = intrinsic clo * amount of body area covered

I sure hope so; that's my understanding also.

So if you are levitating in mid air, completely covered in a sleeping bag, the two are the same. I recollect the calculation changes when you're on the ground, because you're compressing the insulation beneath you.

if hes on a sail boat, humidity may well be a real issue … fog, storms, sleep, rain, etc …

remember that normal high fill down gets affected by high humidity …

synthetic or a least the new fangled water repellent down may be a better bet

;)

You're correct, it is, and heretofore he's been mostly a "synthetic fill" kind of guy, but I know he picked up a resistant down recently.

But putting that aside, can you help me understand the discrepancies in the CLO lists? Or point me to better ones? I really want (need) to understand CLO better.

"They" don't normally use the term clo when talking about down.

I don't think you'll be able to resolve inconsistencies in those lists.

One thing is, all your base layers and under clothes and such have very little clo, so you can just ignore.

If you're doing synthetic, maybe just get a 5 oz/yd2 synthetic bag, which would be 4 clo. If you wear some insulated clothing inside, that should be good down to 32 F. And if you think minimum temperature will be less than that, use Richard's chart to get idea how much thicker you need.

And get a similarly thick blanket or quilt or whatever to go on top just in case. If you're on sailboat, and you're cold, you won't easily solve in the middle of the ocean. Even though you have limited space, there should be room for an extra blanket.

And get a similarly thick jacket and maybe pants. And hat. And maybe double up on everything just in case. Get some fleece clothing too?

Aren't there forums for boaters that cross the ocean? Probably there are types of clothes more appropriate for boating than lightweight backpacking. Like rain/wind wear. When waves hit your boat and you get drenched, different clothing would be appropriate?

I find when people bring a lot of insulation and still get cold the issue is almost always one of nutrition and hydration. Clothes do not make you warm, all they do is keep you from cooling off. If he's not generating enough heat (inactivity, illness, hunger) then virtually nothing will keep him warm.

Given the maritime environment, I would probably just rely on synthetics to make sure he maintains some warmth in a stormy situation. Being at sea you don't have the real opportunity to hunker down and make a fire for warmth, or hike back to civilization if things go south. Look at what British and Scottish climbers wear for winter and your friend should be safe. Those are similarly harsh, cold, wet conditions that should be roughly the same as what your friend will experience.

As for clo specifically, I would trust the stuff on this forum far more than the sites you mentioned. I checked them out once too and basically realized they are based on old rules of thumb far more than any scientific analysis. Also for centuries "down" meant duck feathers which aren't in the same league as goose down of even the lowest quality.

> Aren't there forums for boaters that cross the ocean?

Yes, Jerry, you're absolutely right. I didn't mean to make this a discussion about staying warm on a boat, which is way off topic. Just wanted to underscore my desire to understand CLO — it goes beyond intellectual curiosity.

> I would trust the stuff on this forum far more than the sites you mentioned. I checked them out once too and basically realized they are based on old rules of thumb far more than any scientific analysis.

OK, Dustin, thanks. That's basically what I needed to know. I'll go back and re-read Richard's main posts on CLO (for the third time). Thank goodness that Richard posted the "loft times four times coverage" rule; at least we can make some independent guesstimate of CLO based on a measurement of loft–that's helpful, to be sure.

So…it looks like our own Richard Nisley is on the forefront of CLO science, then! The money I paid for my subscription to BPL is cheap tuition.

PS: Does anyone remember the factor used to compensate for compressed insulation? The down/fill you're lying on doesn't compress to zero, but it compresses a lot. And I imagine it compresses differently for down, synth fill, and pads…

If it's compressed, it's basically worthless since clo for puffy insulation is based primarily on how much air is trapped. Once compressed you're relying on the insulation materials resistance to conduct heat away which can be wildly different than on expects. If compressed fairly tight, I would just say it's negligible and rely on another source of insulation (like a CCF or insulated air pads).

I think if you lay on down or synthetic, it compresses to essentially zero insulation. You need a pad.

That's just where you touch the ground like your hips, shoulders, arms, legs. Other places are insulated at least some, but there's enough area on the ground to be cold.

Well, I'm getting confused so here is what I got now:
first basically clo/oz/yd2
then clo/oz/yd2*oz/yd2 = iclo
then iclo * bsa = clo (of a single garment)
then sum of all clo's per garment = tclo

Am I wright ?

Someone: I think general confusion is evident by the fact that a month passes and nobody answers.

The one I'm most dubious about is your calculation of iClo….I'm guessing the two main terms are divided not multiplied. I do know that iClo = CLO when the insulator completely covers the body. Which is another way of saying that the surface area of the insulator is removed (or "normalized") for the measurement. iClo is a measurement divorced from how much area of the insulating material there actually is. For practical purposes, the surface area of your body [BSA] covered by the insulating material has to be accounted for, which is why we calculate CLO. I think of iClo as similar to a Z-score in statistics, which is a measurement "without units." (Sort of. The units are standard deviations from the mean.) If you know the iClo, you can calculate CLO for any range of garments made of that same insulator.

In thread 18950, the seminal thread on this topic, in the main graphic, Nisley is giving iClo values for specific clothes, not CLO values. Deep in the thread he states: "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." Yet it seems most people read Nisley's iClo chart as a CLO chart, which causes people to fabulously overestimate the warmth of their gear.

Your other definitions match my understanding. The important, "non-theoretical" number for calculating your comfort level at various temperatures is Total CLO.

I've yet to see a discussion of how that must be balanced. I can imagine wearing a 3" loft parka and no pants, having a good tCLO, and still freezing to death. I'm curious of there are ideal proportions: 75% on the trunk and head, 25% everywhere else, or something like that.

I think clo = iclo * fraction of body area covered – they both have the same units because fraction of body area covered is unitless – no ounces, yards, watts, or anything

I think it's best to have about the same clo over your entire body

Except maybe less on your head so you can see, breath, and move your head around (minimize Michelan Man effect)

And maybe a little less on arms and legs to minimize Michelan Man effect, and also, since the skin temperature is a little less, the insulation is a little less efficient at reducing heat loss

I mailed Richard several weeks ago about my assumptions and he replied they were correct. I forgot to update that. Sorry for that.