Why the obsession over sleeping bag/quilt warmth but not sleeping pad warmth?

[Derek M.]

I'm genuinely curious to know why there seems to be so much attention given to the exact warmth rating of sleeping bags and quilts around here (e.g. "is it a 30 degree bag or a 20 degree bag?", etc…) but such little nitpicking about the precise warmth of sleeping pads?

I'm making a generalization here, of course, but I just see very little obsessing over exact sleeping pad warmth (R-value) here on the forum and I'm wondering why that is?

On the face of it, it seems like the warmth of a sleeping pad would be just as important as the warmth of the sleeping bag or quilt that is used with it, since the sleeping pad is just as integral a part of the "sleeping system" as the bag.

What am I missing?

Obviously I see people talking about pads that can be used in the winter (i.e. on snow) versus pads that are more limited to snow-free 2 or 3 season sleeping, but the attention to detail beyond that seems somewhat diminished (e.g. comparing a pad with, say, R-value=3.1 vs. one with R-value=3.9).

Why is that? Presumably, these differences are significant, no?

[Joel Benford]

Hmm.

I aimed my system at around -5C… -4C pad, -1C bag, partly compressible clothing.

But you don't hear about pad temps so much, I agree.

The only reason I can offer is that I don't want to over-specify a bag because too hot is uncomfortable, whereas rightly or wrongly that doesn't seem to be an issue with the mat. So the bag I want to get just right, the pad only needs to be warm enough. Thus, more attention on the bag.

edit: Perhaps it's also common knowledge that there are lies, damn lies, and American sleeping bag ratings. Whereas only people who read the air mat SOTM in full realise the same goes for mats.

[James Marco]

Only about 1/4 or so of your conductive heat loss is through your pad. A few degrees of variation between a winter pad and a summer pad are generally enough to make up for most of the inbetween temps. I *might* use a thicker bag a bit sooner in fall, but continue to use the same pad.

There is a big difference in the "ground." Dark, wet soils are more conductive of heat than soft dry duff. Rock and ice is more conductive than snow by a large difference. A summer pad (say a NeoAir) may be fine down to -20C when put on top of forest duff. Put the same pad on open rock on a hill top or out in the middle of a frozen lake, and it could not keep you warm at 0C.

There are three forms of heat to worry about with pads: Conductive, Convective and Infra Red. Condictive and Infra Red happen in all directions, but the heat always has a gradient…ie, it always has a tendency to rise(close enough, anyway.) A NeoAir Xtherm has two baffles inside to hold heat next to you. Yet your Down Bag has literally thousands of smaller air pockets. When IR warms something up, it will translate the radiation to conductive or convective heat as a molecule absorbs the energy. It might re-radiate IR or it might simply loose portions to the surrounding area as lower energy condictive processes. So, it is more or less, statistical. Much of the IR will be trapped and released below you warming the air/object you sleep on. Heat rises to rewarm your body. So, critical temps for pads are very different depending on the pad and surface it is on. Most is simply recovered, so, a thin 1/2" foam pad is often enough for most campers on forest duff, right down to freezing. Mostly, I worry about comfort. I need a thicker 3/4" to 2-1/2" pad in summer. Maybe a thick 3-1/2" pad in colder weather.

Lighter, less dense materials will warm quicker (and cool off quicker) than heavy, dense pads. How quickly something does this often influences your perception of warmth, too.

[Matt Dirksen]

" but the attention to detail beyond that seems somewhat diminished (e.g. comparing a pad with, say, R-value=3.1 vs. one with R-value=3.9).

Why is that? Presumably, these differences are significant, no?"

While we will never quite know the answer to your question, here's my take.

1) For ages, it has been drilled into our collective consciousness that the THREE most important pieces of gear to consider are the pack, tent, and sleeping bag. (Listing R values is a relatively new thing in the world of sleeping pads.) Telling everyone there's now FOUR pieces would probably be a buzzkill.

2) Although I see the occasional $$ sleeping pad in my scout troop, there are a handful of boys who don't even use a pad – unless its winter. My son is perfectly content on an 1/8" eva pad… (For now.)

3) As you indicated, I, too, believe it IS a value of diminishing returns. In weather above freezing, there really is little difference between 3.1 and 3.9.

[James holden]

folks understand a simple number and concept … -10F, +10F, etc …

its a simple number that folks believe will keep them "warm" and folks at home "get it" as they understand that more blankets keep em warmer … they dont understand how their mattress and the fact they are off the floor keeps their backside "warm"

until the pad industry comes up with such a simple number, people will always obsess over bags rating over pads

of course plenty of folks get confused by PROPER en-ratings and their differences … how many actually take the time to make sure that the "30F" bag is rated to at least 0C en-lower limit for mens, or 0C en-comfort for women?

simple concept, simple numbers … thats what folks get

its THAT simple

;)

[Jerry Adams]

In addition to other comments

Roger did an article about sleeping pad warmth, there's some interest

You can have a warmer pad and colder sleeping bag or vice versa. So if you have one pad, you can have different sleeping bags to accomodate different temperatures

I think when they rate sleeping bags, there's an assumption that for much colder temperatures you use a warmer pad

Maybe it's partly just because other people are talking about sleeping bags more. In an alternate universe, people might talk about pads more. But, since heat rises, in most of the alternate universes people talk about sleeping bags more, in only a few do people talk about pads more…

[J Mag]

I think it is pretty simple… because one pad will easily cover 3 seasons in 90% of the country (which is when most people are out backpacking anyway).

On top of that, you can add a 3 or 4 oz foam pad to cover winter needs (again for the majority of backpackers) as long as you have an appropriately rated quilt.

[J R]

In addition to what others have said…

My guess, and it is only that, is that bags/quilts are rated by temperature, which is a measurement we can relate to and is directly relevant to the idea of "warmth." Pads are rated by R-value, which we all have a vague intellectual understanding of but it does not directly translate into a particular idea of "warm" or "cold." A 30F bag will keep you warm in what kind of weather? Oh, about 30F (I know, it depends, but that's the immediate intellectual connection). A pad with an R-value of 3.2 will keep you warm to…what? Dunno.

I also think that level of warmth from the bag/quilt is seen as more independent of the pad, while the level of warmth from the pad is seen as very dependent on the bag/quilt. In fact they are two parts of an integrated system, but I don't think that most users think of it this way.

[Dale Wambaugh]

Good question! It is kinda loose, like not including trekking poles in your base weight (looks at ground, clears throat).

My thoughts on the phenomenon:

A basic pad covers most three season use and most hikers are summer campers. Any old CCF pad will do, and it's hard to buy one that isn't 3/8" thick. The thin Gossamer Gear pads are one divergence, and I'll bet the percentage of users for 1/8" pads is tiny.

One of the major gear list divergences from UL canon law is with pads. Basically, people tend to take thicker pads, but for soft comfort rather than temperature.

I think r-value is more significant to quilt users. With all the therorizing about compressing your insulation under, a sleeping bag is still warmer and I'll bet that the majority are still using bags vs quilts, lessening the impact of the pad r-value.

Read up on winter camping and there is plenty of chatter on pads, with many doubling a couple UL pads to get the r-value needed for snow camping.

There's definitely lot more chatter on r-value of the super light air pads than CCF foam versions. I have a dim recollection of some R-value/weight charts, but the discussions seem to be more concerned with "I have chosen x pad for soft sleeping comfort, how low can I go temperature wise?" or "how can I supplement my cushy pad for colder weather?"

Only the SUL lists are really pushing the limits for lowest weight for R-value with many incorporating the pad in the pack suspension, mostly CCF.

I went Gossamer Gear to get the R-values on their foam pads, knowing that they are a leader in light CCF models and lo and behold, they do not give R-values for their pads. That seems to support the OP's point.

[Michael Gunderloy]

A bit out of date, but here's a start at a comparison chart.

[Greg Mihalik]

A chart with manufactures numbers no less, some to be taken with a pinch of skepticism –

NeoAir XLite Womens – 3.9

[Woubeir (from Europe)]

"Roger did an article about sleeping pad warmth, there's some interest"

Do you have a link or so because I can't find it ?

[Jerry Adams]

http://www.backpackinglight.com/cgi-bin/backpackinglight/testing_thermal_insulation.html

[John Klinepeter]

Here is an old gem from 2009 that I bookmarked. It is useful as a starting point for figuring out insulation requirements, both pads and other sleeping gear, when viewed in total. See Richard Nisley's table about 2/3 of the way down the page.

Reference

The conclusion that can be reached is that sleeping pad insulation is important. It doesn't answer your original question about the obsession but maybe provides some insight. My guess is that many more insulated inflatable pads have been available for the last several years vs. the uninsulated R 1.0 swimming pool pads that were common. It is my perception, another guess, that there are fewer "my sleeping bag is cold" threads in recent years due to the availability of warmer pads.

May everyone have many more vexing obsessions (myself included)!

[James holden]

I went Gossamer Gear to get the R-values on their foam pads, knowing that they are a leader in light CCF models and lo and behold, they do not give R-values for their pads. That seems to support the OP's point.

for their evazote foam pads … you can simply look up the equivalent on MECs website … they give R values for all of em

http://www.mec.ca/shop/sleeping-pads-foam-pad/50050+50877/?h=10+50050

of course for canuckleheads, buy it from MEC as the ones they sell are made in CANADA

;)

[Don Selesky]

"There is a big difference in the "ground." Dark, wet soils are more conductive of heat than soft dry duff. Rock and ice is more conductive than snow by a large difference. A summer pad (say a NeoAir) may be fine down to -20C when put on top of forest duff. Put the same pad on open rock on a hill top or out in the middle of a frozen lake, and it could not keep you warm at 0C."

Interesting. I wasn't aware of the large difference between ice and snow, or that rock was a heat sink.

About where would still air fall in the spectrum? I'm thinking specifically about hammock camping, and ignoring the issue of air movement under the hammock.

[James Marco]

Yeah, you can think of ice as a rock like substance. It has little or no air space. Snow may be as much as 90% air space. It is an excellent insulator. Sleeping on ice may cause some ice to melt from pressure. This will suck heat a lot quicker than just snow. Sleeping out on a lake is NOT recommended (I was cold for two nights on Racquette Lake in the ADK's.)

Air (still or confined air) is generally considered to be an R value of around 1 per inch. This will depend a LOT on the shape doing the confining, ie: concave vs convex. I tried hammocks, but with the breezes, it was likely less than R.5 and cold, even at 50F. Most people in the NE use some sort of heavy underquilt or padding. The weight stays the same as a bag and a pad. No benefit here…(well, sometimes it is better, sometimes it is worse. Hammocks are just a bit more variable.)

[Aaron Sorensen]

If I take a quilt I am normally a little cold in at 30 degrees and 3 ounces of down, I will be warm.
There is no possible way to do this with 3 extra ounces of pad.

This is why I usually carry a 10 degree warmer quilt and an 1/8" closed cell pad.

[Jerry Adams]

If you look at clo/oz/yd2, or R/oz/yd2, or Rsi/g/m2, pad is much less than sleeping bag. The pad has to hold up your weight without compressing too much so it is much heavier. Down, or even synthetic is way lighter.

Perhaps another reason for "obsessing" over sleeping bag instead of pad.

[Miner]

Given that I spend <$30 for a lightweight pad and over $300 for a good lightweight sleeping quilt/bag, I think it should be obvious why many spend more time thinking about it. And in my case, since my pad weighs under 8oz while even the lightest 20F quilt can be at least 18oz, there is more weight reduction potential in the quilt/sleeping bag.

It's not that many don't consider the pad, its just that most of us have something good enough where the ground isn't the first thing that makes us cold at night though campsite selection can be a factor here as well (eg.a thick layer of duff is warmer then hard bare ground). Though some here do obsess over pad comfort more then others and willingly pay the weight penalty for it. There are plenty of threads related to pad comfort floating around here.

[Don Selesky]

I generally use a pad underneath me in a hammock, a tarp that extends below the hammock, and possibly a nylon "sock" to prevent breezes from directly touching the hammock bottom. I'll often double up on the pad in winter, just to be sure I don't get cold. Haven't had an issue with being cold down to at least 0F so far.

[Derek M.]

Hmmmm.

Some good comments so far.

I have to say I'm still not fully convinced of this idea that a 3/8 inch thick foam pad somehow just hits a magic warmth value that allows nearly everyone to sleep warmly in nearly all the conditions commonly encountered by 3 season backpackers in the US. This just seems very fishy to me. Way, way too convenient.

Why can a pad never be too hot in practical terms but a sleeping bag can? This just doesn't really seem logical to me.

My suspicion is that while people seem to always blame their sleeping bag if they are too warm or too cold, the sleeping pad probably plays nearly as important a role in determining this outcome.

It's just my hunch, which may be wrong, but this "one-warmth-fits-all" idea of sleeping pads just doesn't pass the smell test for me right now.

If someone has data to resolve this issue, please do share.

[Roger Caffin]

> this "one-warmth-fits-all" idea of sleeping pads just doesn't pass the smell test for me

Well, how many different mattresses do you have at home? Or do you sleep on the same mattress summer and winter, just vary the amount of covers?

I wonder what the R-value of a typical home mattress is? Probably up around 20 or more?

Cheers

[Derek M.]

Roger,
I have one mattress at home. I'm sure it's R-value is quite high, and I am often very hot on it. Like, wake-up-sweating hot. There have been times where I am cold from not enough sheets but hot on my back from the mattress warmth.

Again, this argues for exact sleeping pad warmth being somewhat important.

I think that just because it might be impractical, or too much of a bother to change out pads for different conditions, doesn't make this effect any less real.

For some reason, it seems that we have simply accepted sleeping pads being either too warm or too cold, while at the same time focusing quite intensely on the precise warmth of sleeping bags.

I still find this very interesting.

Maybe it's because we are so used to our backsides being too warm due to many of us sitting in well padded (and highly insulative) chairs all day?

Now that I'm focusing on it, my backside is rather warm right now as I sit in my chair. Hmmmm…

[Matt Dirksen]

"I am often very hot on it. Like, wake-up-sweating hot."

The mattresses "R" value probably contributes very little to this experience in relation to the air temp, relative humidity, what you ate before you went to bed, and your blankets over top of you.

With the exception of hammock & winter camping:

Precisely matching the "R" value of a sleeping pad is simply never going to be as important as having the right system over top of you while you sleep. Remember, the pad is nether "hot" or "cold", you are. One could bring a super "warm" pad and forgo some insulation over top, but its highly unlikely that this approach would ever offer any weight savings. Again, the quickest & most efficient way to maintain warmth, is from regulating the conductive & convective heat loss – over top of you. It takes a good number of freezing days to cause the ground to start to freeze, where the temperature difference between you and that ground becomes an important consideration.

In our homes, the code required R values of our walls and ceiling are significantly higher than the required R value under our floors. Moreover, a square inch of air gap in a home is equuivilant to eight square feet of no insulation in a wall. That's how siginifcant convective heat loss can be.

Having sold a ton of sleeping pads in my past life, I can assure you that sleeping pad comfort always took precidence over warmth. If someone needed more insulation, they'd buy both the comfy pad and grab the blue foam pad next to it and be done with it. Buying a sleeping bag typically took a serious shopper hours, days, and even months of deliberation. Usually the pad was a fifteen minute decision.

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