Confused or TQ+UQ temperature ratings... Please help.

[ckmaui]

might say that depend each person has his own comfort level is what I would take away and these are all just guidelines



for me its about the top quilt temp I have a 0 under and 20 top and think 20 is the limit and at 10 I would be to cold


to me it comes down to the under being the most important layer and one that will determine the most comfort within reason
mainly cause of fit etc....
meaning say its 50 out and you have a good fitting 50 a poor fitting 20 will not keep you as warm and you will get cold spots

It seems the most important point gathered from this discussion is that a lower rated UQ paired with a higher rated TQ will help to bring the TQ rating lower. In example, a 20* UQ and a 40* TQ will help to achieve 30* or 35* rating. Which could be useful if you're looking to cut ounces and you don't have a 30* setup.

[WalksIn2Trees]

The actual science is that heat will flow from a high pressure area to a low pressure area through a given material at a given rate which is proportional to the differential between the two zones. The equation and most of the variables are available in the course guide for home energy efficiency courses available for study at a college near you....I think they are available through BPI as well. The only variable that isn't readily available is the one for down. I found one on a website for down parkas, but I doubt know how accurate it is, and I had to convert it from metric, so in not sure how accurate my own conversion is. In the equation though, you substitute the down for your house's walls, and your body heat for the output of a furnace. I set mine up so I could numerically try different thicknesses at different temperatures ranges, using some known quantities of equipment I own to determine my personal comfort level. Real world, I didn't get to test against my worst case, but it looks like actual performance might be better than anticipated

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[Just Bill]

There is science- https://en.wikipedia.org/wiki/Clothing_insulation
The basic formula is 1 clo = 0.155 K·m²·W⁻¹ = 0.88 R
Most of us know R-value and CLO is a similar system to rate clothing.

As Mr. Arrowhead pointed out though- the science becomes a bit less scientific when you realize that the key variable in that formula is Met- which is basically the individual metabolic rate. Simplest way to put it- you are a lightbulb.
But are you a 40w, a 60w, or an 80w bulb?
Gear does not create heat, it only retains it. The key here is how much your individual bulb puts out.

Even the "best" most scientific rating system we have (The EN 13537 system) can't manage to spit out a rating; rather they generate 4 ratings. https://en.wikipedia.org/wiki/EN_13537

From the article-
The standard measures four temperature ratings:
Upper Limit — the temperature at which a standard man can sleep without excessive perspiration. It is established with the hood and zippers open and with the arms outside of the bag.
Comfort — the temperature at which a standard woman can expect to sleep comfortably in a relaxed position.
Lower Limit — the temperature at which a standard man can sleep for eight hours in a curled position without waking.
Extreme — the minimum temperature at which a standard woman can remain for six hours without risk of death from hypothermia (though frostbite is still possible).

For the purpose of these measurements, a "standard man" is assumed to be 25 years old, with a height of 1.73 m and a weight of 73 kg; a "standard woman" is assumed to be 25 years old, with a height of 1.60 m and a weight of 60 kg.

So that's a relatively healthy young person in good shape- as in, we can assume their lightbulb puts out a steady bit of Watts to "prime the pump" and keep them warm. Even when the "person" is a lab dummy.

It is also worth noting that the standard clothing worn is a base layer and light beanie (about .5CLO or 4*F worth of insulation).

What this really tells us overall- is a rough idea how gear compares to each other. We as the end user have to adjust for our own personal experience and as a group we can get together on places like this to establish a real world average in conditions that don't involve laboratory conditions.

Now to answer the "unbalanced" rating question-
That's not as confusing as it would seem. You don't have to worry too much about heat rising or the different types of heat loss- though those all matter a good bit. *(caveat below)

In the air- your Underquilt generally covers 2/3rds of your body. It further wraps up past you and up the sides of a typical gathered end hammock. You could make the argument that a decent bit of heat in your UQ then migrates up the sides (rises) and slips right out the top.

Your TQ only has to insulate a relatively small area across the top third of your body. Further, your TQ is inside your hammock and sheltered from wind- which explains why hammock folks consider an UQ protector a benefit, but nobody is rigging up a TQ protector to minimize wind loss.

On the ground- your TOP quilt takes the brunt of the job, covering 2/3rds of your body while your sleeping pad is neither exposed to wind nor has to insulate as much area.

Experienced ground dwellers will note that they can "stretch" a given sleeping pad much further than it's rating with a warmer Topquilt (sleeping bag) while hammock folks claim the opposite. Mayhap not the place for it here- but at WB or BPL you will find many ground dwellers who use a 20* quilt over a 40* pad successfully to freezing.

While you won't find it in an engineering textbook here's a bit of common sense math:
If 2/3rds of your body is covered by a 20* piece, and 1/3rd is covered by a 40* piece that is (20+20+40)/3= 26.67 degree rating.
Now if we balance that against trusted field reports from experienced folks... I don't care what the science is, that's a good bit of backwoods math you can count on.

However- you can bundle up until you get mistaken for an inuit- but if one piece of your body is cold (ears with no hat, hands with no gloves, etc) then you are COLD. CBS involves one fairly fatty and muscled well insulated posterior on an otherwise warm body- yet prevents sleep.

So while balancing ratings can be an effective tool- if one piece of the system fails then the whole system fails. Weakest link and whatnot if'n you prefer that analogy.

*caveat*-
Unlike a top quilt, which does get to take advantage of warm air's property of rising...
A pad or underquilt does not.
Your warm air is not magically flowing downward and residing in your UQ- farts and such excepted of course.
Further an UQ is also subjected to many more factors likely to strip warmth away. Unlike a pad, an UQ does not rely on foams, reflective barriers, or other things designed to resist that type of heat transfer.
It relies on down and little more than a calendared or DWR shell.

Now- in real life- I went from ground to air, and I make gear. I was stupefied that pads I used on the ground lost 20* or more of performance when used in the air. I was mystified that 2" of down UNDER me- did not work the same as 2" of down OVER me on the ground- that's even counting in the 2/3-1/3 rating scenario.

I am now quite firmly convinced that a given loft of down WILL NOT achieve the same rating in an UQ as it will in a TQ.
Now if you go with some big winter tarp and UQ protector and other tricks to mitigate some of the other forms of heat loss the UQ takes... maybe this gap is not as big.

But apples to apples- hang an UQ in the air or use a TQ and cowboy camp on the ground- I see at least 10* difference in performance. I saw as much as a 20* loss with an air pad like an Xlite by thermarest.

I can't speak for the vendors in biz now or how they calculate their fills.
I do think that in time we will come to find that a new loft chart is needed specifically for underquilts using down.

And I think that you could easily re-run my example above to match field experience in varied conditions:
A 20* UQ, dinged down to 30* in real life... with a 40* TQ works out to (30+30+40)/3=33.33 degrees.

So 20 under and 40 over gets you to freezing in the real world under average conditions?
Yar- I think that scenario matches pretty durned well with what most folks use for freezing who vary the rating of their pieces.

A zero under and 20 up top- Ding the UQ down 10 degrees and you have (10+10+20)/3= 13.3 degrees
Which is also a combo I see frequently here and most would agree is a solid expectation in real life for it.

SO- I would strongly encourage you to mix and match your ratings if you are looking to spare a little weight, cost, etc.

Or even to push a system a bit in total. Don't feel like running the numbers at the moment but:
One might consider comparing a 30* set to a 20/40 set for example...

Even better- we all pack our fears to an extent and get nervous here an there... IF CBS is the big enemy to sleep in a hammock- doesn't a 20/40 combo make greater sense than a 30* matched set? You've literally covered your ***, but not broken the scale or the bank in the process.

Coupled with the fact that spare clothes could be laid on top of you (but not so easily under you)- going a bit light on the top piece seems a very practical winner for the weight conscious hanger.

[sidvicious]

i haven't read all the replies...........so.........

the UQ is the key to hammock warmth, all things considered. on cold nights the TQ can be a non-factor if the UQ isn't "proper".

my continued suggestion to folks is, if they can only get one quilt set, and they'll be camping in below freezing conditions, get a full length 0* UQ. you cannot get too warm when its cold, at least not from the UQ end of things.

sv-

[hlee00-05]

Are you sufficiently warm in your home bed? Are you as warm sleeping with those sheets and blankets on top of you, on the kitchen floor? Are you sufficiently warm in your bed, all night, without any blanket?

The answers to these questions are all "maybe." We are not dealing with objective scientific observables. We are dealing with comfort. You might as well be asking "how long is a piece of string?" That said, you are more likely to stay comfortable, for the entire night, if ALL of your insulation is rated to the temps you are experiencing- and is used correctly. Are there people on either end of the spectrum? Yes, some will be cold at 50F with 0F rated equipment. Others will be hot at 0F with 20F rated gear. So, will YOU be comfortable without some gear, or with under rated gear? I don't know, but I really believe "that it is better to have and not need than to need and not have..."

[WalksIn2Trees]

If you know anything about plumbing, or electrical systems, this functions similarly. if your quilt was a tube, and the mass of your body wasn't blocking the flow, it would function the same. actually it's a lot more like electrical wire than plumbing because it leaks radially.

For the most part, the complexity of real world use is far more detailed than can be accommodated by simple scientific formulas. My father, when designing his energy efficient SIP home, used software to calculate how robust of a heat source he would need. It had calculations for things like: the interaction of the surface friction of his proposed siding type with the molecules of air as the passed in high wind during extreme winter conditions (this friction creates a sort of skin of air next to objects which adds to the insulation. You can see it when cooking on your grill, is what makes your Coleman fuel lanterns mantel work, and is the same reason that your Bug-net makes your hammock a little warmer, even though it's full of holes.) It took him a week to enter all the data into the software but even with the inclusion of such tiny influencers, he still ended up with different (better) results and unforeseen consequences... His house was too efficient for his outdoor wood furnace. This sounds like it should be good, but what it meant was that he was burning wood just to keep the furnace running when the thermostat wasn't calling for heat. On a sunny winter day, he has to open windows because it gets too hot.

So with that in mind, consider our situation. Assume for the moment they both TQ & UQ match. Yes heat rises. But only as long as that's the only differential involved. Once you're in a cocoon of down, you're changing that differential, slowing down the heat transfer rate. That cocoon is acting like a lantern mantel so you end up with equal dispersion... Except for the effect of gravity which means heat goes out the top, and cold comes in the bottom... But your body isn't just losing heat, it's PRODUCING heat... Which means that the inside of your cocoon is a constant positive pressure zone. This works against the cold that would be coming in, but only as long as the differential is in your favor. If the wind is stronger than your body produces heat you get a cold back. If the temperature differential is colder than the amount of heat you produce, you also get a cold back. If the wind hits you from the side, you get higher pressure of cold on one side, lesser pressure across the top and bottom, and low pressure on the other side.

The way down itself works, you have incrementally less pressure difference from the outside to the inside, meaning the outer air pockets lose more heat than the next inner air pockets because the outer one helps insulates the inner. This insulating effect adds up as you go further in until eventually it equals out and the loss rate becomes a constant, at which point that constant becomes the rate of heat flow for goose down. Also known as down's "Heat Transfer Coefficient".

Mind you, I'm no expert... This is based on what I remember from my Home Heating Energy Efficiency courses that I took in 2008, most of the focus of which was split between insulation and furnace/duct efficiency. FYI...One thing I learned is that you reduced heat loss MOST by improving insulation, not by buying new windows... The amount of $avings you get from new windows is tiny compared to what you get from plugging up the other holes. You definitely should plug your insulation before considering replacing windows. Most people focus on windows because that's something they can SEE, but plumbing and electrical chases contribute to stack effect along with places where rodents have tunneled through insulation and places where insulation installers cut corners or left gaps unintentionally... In that case, buying new windows actually adds to stack effect which costs you $ because it increases the airflow up through the middle of your house from your basement through your roof.

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[sidvicious]

If you know anything about plumbing, or electrical systems, this functions similarly. if your quilt was a tube, and the mass of your body wasn't blocking the flow, it would function the same. actually it's a lot more like electrical wire than plumbing because it leaks radially.

For the most part, the complexity of real world use is far more detailed than can be accommodated by simple scientific formulas. My father, when designing his energy efficient SIP home, used software to calculate how robust of a heat source he would need. It had calculations for things like: the interaction of the surface friction of his proposed siding type with the molecules of air as the passed in high wind during extreme winter conditions (this friction creates a sort of skin of air next to objects which adds to the insulation. You can see it when cooking on your grill, is what makes your Coleman fuel lanterns mantel work, and is the same reason that your Bug-net makes your hammock a little warmer, even though it's full of holes.) It took him a week to enter all the data into the software but even with the inclusion of such tiny influencers, he still ended up with different (better) results and unforeseen consequences... His house was too efficient for his outdoor wood furnace. This sounds like it should be good, but what it meant was that he was burning wood just to keep the furnace running when the thermostat wasn't calling for heat. On a sunny winter day, he has to open windows because it gets too hot.

So with that in mind, consider our situation. Assume for the moment they both TQ & UQ match. Yes heat rises. But only as long as that's the only differential involved. Once you're in a cocoon of down, you're changing that differential, slowing down the heat transfer rate. That cocoon is acting like a lantern mantel so you end up with equal dispersion... Except for the effect of gravity which means heat goes out the top, and cold comes in the bottom... But your body isn't just losing heat, it's PRODUCING heat... Which means that the inside of your cocoon is a constant positive pressure zone. This works against the cold that would be coming in, but only as long as the differential is in your favor. If the wind is stronger than your body produces heat you get a cold back. If the temperature differential is colder than the amount of heat you produce, you also get a cold back. If the wind hits you from the side, you get higher pressure of cold on one side, lesser pressure across the top and bottom, and low pressure on the other side.

The way down itself works, you have incrementally less pressure difference from the outside to the inside, meaning the outer air pockets lose more heat than the next inner air pockets because the outer one helps insulates the inner. This insulating effect adds up as you go further in until eventually it equals out and the loss rate becomes a constant, at which point that constant becomes the rate of heat flow for goose down. Also known as down's "Heat Transfer Coefficient".

Mind you, I'm no expert... This is based on what I remember from my Home Heating Energy Efficiency courses that I took in 2008, most of the focus of which was split between insulation and furnace/duct efficiency. FYI...One thing I learned is that you reduced heat loss MOST by improving insulation, not by buying new windows... The amount of $avings you get from new windows is tiny compared to what you get from plugging up the other holes. You definitely should plug your insulation before considering replacing windows. Most people focus on windows because that's something they can SEE, but plumbing and electrical chases contribute to stack effect along with places where rodents have tunneled through insulation and places where insulation installers cut corners or left gaps unintentionally... In that case, buying new windows actually adds to stack effect which costs you $ because it increases the airflow up through the middle of your house from your basement through your roof.

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you typed all this on a phone?

you're a monster, man

sv-

[WalksIn2Trees]

you typed all this on a phone?

you're a monster, man

sv-

It's a tablet, Sid, but even so...

By the way, to anyone using a Samsung... Do yourself a favor and switch from Samsung's on screen keyboard to Google's... The swipe detection is way better, much less frustrating to use in regards to its choosing the word you're actually trying to spell. Plus you can add to your own dictionary, with shortcuts to words you use a lot for instance, if I type "bn" that's my shortcut for "Bug-net" which it offers in the suggested words bar for me to click if that is indeed what I want to use.

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