Does inflating a sleeping pad with your breath really lower it’s R-value ?

[Nicholas P]

He’s at it again. A new Gear skeptic video casting doubt on the long touted claim that repeatedly inflating a pad with one’s breath will lead to a noticeable drop in R-Value .He also addresses the fear  of potential mold growth caused by this practice.
Interesting Video and it seems like it may not be a big deal to go pad to mouth after all, but I think it’s possible more extensive testing of pad performance in sub freezing temperatures over many consecutive nights could yield different results.

https://youtu.be/sb4Y2pE8V18?si=mj7TyDeMjD5UUwCI

[Jerry Adams]

I’ve weighed pads over time and they don’t gain weight.

If they grew a lot of mold they would gain weight.

If there was significant water in them they’d gain weight.

I’ll have to watch that video, thanks

[jscott]

Jerry always runs tests to determine the validity of common sense claims about gear. For example he proved that placing a lid on a pot does nothing to decrease boil time. I and many others found this offensive. My grandmother and my mother placed a lid on their pots when they boiled water for cooking. So it’s down to my grandmother versus modern science.

I choose my grandmother–because I think she was right. But back on topic, I use a schnozzle, not only because where I hike it tends to be low humidity, and so it pumps dry air into the pad; but because it’s much more quick and easy to inflate a pad that way. Inflating a pad by breath at 10,000 feet takes some time and effort!

Human breath is moist. I do wonder about mold growth in a pad overall, and especially as it might be encouraged by warm, moist breath inflating the pad repeatedly.

I’ve never thought of this affecting the R value.

I will stipulate that I’m a bit of a hypochondriac. A bit. And so I worry about the health of my gear. And I hate mold.

I go back and forth between being grateful to Jerry for alleviating my fears through scientific analysis, and saying “science be damned!” I put a lid on my pot when I’m boiling water.

[Todd T]

But back on topic, I use a schnozzle, … because it’s much more quick and easy to inflate a pad that way.

^This.  I couldn’t care less whether or not breath is bad for my pad because I’ll be using my Schnozzel, which doubles as an excellent dry bag for my camp clothes and sleeping gear.

[jscott]

Yep, I think the Schnozzle might be the poster child for light hiking gear. Especially since it works great as a dry bag. I’m easily able to put my sleeping bag in its stuff sack and my down jacket and other essential items inside of a Schnozzle inside of my pack. The damn thing’s brilliant!

[Jerry Adams]

I think you’re confusing me with the gear skeptic jscott : )

I always use a lid, to keep dirt out

I’ve heard that “a watched pot never boils” but the gear skeptic has proved that wrong

 

[jscott]

Jerry, true, when I wrote the above post I made you sound like the Gear Sceptic. Still, you are a welcome voice of reason and measurement when it comes to analyzing gear.

[Jerry Adams]

I finally watched the video, thanks Nicholas

We saw the back of his head a little, beyond just looking at  his hands.  Very interesting.

I’ve had a couple thermarest self inflating pads that delaminated.  I should have cut them open to look for mold.

The reason insulation loses insulation value when wet is it matts – the thickness decreases.  This wouldn’t happen in an air pad filled with insulation.  Another thing is that if the insulation gets wet, you will dry it out from body heat.  The evaporation of water loses heat so that has the same effect as losing insulation, but an air pad is contained so there’s no evaporation.

[Nicholas P]

The point of this video is not to advocate against the use of pump sacks ( relax nobody’s trying to take away your Schnozzels) this video is part of a series of videos by Gear Skeptic that’s goal is to scrutinize the legitimacy of some of these commonly repeated claims in Backpacking that don’t seem to have any real Data to support them.I use a pump sack as well ( nyloflume liner with valve adapter) and I fully intend to continue using it. I also use a lid on my pot because like Jerry said it keeps stuff out of the water, but it doesn’t mean I found that whole series of experiments  of literally watching water boil uninteresting.

I for one did initially start using a pump sack because of the R- value claim and as I understood it , it was only supposed to be a concern for prolonged cold weather camping.The Mold thing I was less concerned about because I remember Thermo-rest saying they use antimicrobials inside of the pad and that they had never had a complaint of mold on the inside. Anyway I have been guilty of perpetuating the R-value claim  with  some people I see that don’t use an inflation device , so I guess at the very least I can stop doing that.

[Terran Terran]

How do mold spores get inside the pad? What do they feed on? Blow in warm moist air and expel cold dry air could possibly lead to condensation and possible accumulation. I cut open an Exped pad after 10 years of use. It was in excellent shape other than some blown baffles. It was always easier to use the schnozzle.
So…speaking of moist breath… if I stick my head inside my bag, how much moisture am I actually dealing with?

 

[Nicholas P]

Haha Jerry ,

maybe he will eventually let another body part slip , come to think of it maybe the true intent of these videos is the worlds slowest and driest strip tease.

Anyway do you think we can say he “handedly” dispelled these myths . After all  I guess it was pretty “heady” stuff . Right!

[Jerry Adams]

I watched his video asking if the head really loses half of total heat loss

I think this is totally just that if you have insulation everywhere but your head, then half your heat loss will be through your head.  It’s not that there’s anything magic about your head, just that you need to have insulation everywhere.

Right at the beginning of the video the gear skeptic sort of dismissed the case of no insulation on your head and called it an exaggeration, no one doesn’t wear a hat when it’s cold.  But that’s what it is.

He went on to talk about some interesting things though.  Lund and Browder chart.  Head has 4 times as many blood vessels on skin, no vasoconstriction,…

[Stephen Seeber]

Sounds like a perfect question for the chatbot.  Here is his/her answer:

The thermal resistance of a material or substance measures its ability to resist the flow of heat. It is typically represented by the thermal conductivity (k) or its reciprocal, thermal resistivity (R), which is the thickness of the material divided by its thermal conductivity.

For dry air, the thermal conductivity varies with temperature and pressure but is approximately 0.024 W/(m⋅K)0.024W/(m⋅K) at standard temperature and pressure (STP), which is 273.15 K273.15K (0 degrees Celsius) and 101.3 kPa101.3kPa (1 atmosphere). Therefore, the thermal resistivity of dry air at STP is approximately:

Rdry air=1/dry air=10.024 W/(m⋅K)≈41.67 m⋅K/WRdry air​=kdry air​1​=0.024W/(m⋅K)1​≈41.67m⋅K/W

For saturated air (air that contains the maximum amount of water vapor it can hold at a given temperature and pressure), the thermal conductivity is slightly different due to the presence of water vapor. However, the difference in thermal conductivity between dry air and saturated air is generally considered negligible for practical purposes. Therefore, the thermal resistance of saturated air is also approximately 41.67 m⋅K/W41.67m⋅K/W at STP.

It’s important to note that these values are approximate and can vary with temperature, pressure, and humidity. Additionally, when considering the thermal properties of air in practical applications, factors such as convection and radiation heat transfer also need to be taken into account.

In the winter, if I blow up my sleeping pad with my breath, I would have to do so repeatedly because the warm air would quickly cool and lose volume.  Instead, I use a battery-powered Tiny Pump 2.

[Nicholas P]

Cool , thanks Jerry I’ll have to give it a watch.I think I like where he’s  Headed with this – sorry couldn’t help it , last time I promise.

[Nicholas P]

Stephen , great  point about the loss of volume do to the cooling off of warm air .

[Todd T]

So…speaking of moist breath… if I stick my head inside my bag, how much moisture am I actually dealing with?

A lot, in my experience.  I’ve awakened to a sopping wet bag all around where my face was.

[SIMULACRA]

Chat(ro)bot, computer generated intelligent algorithms, are known to give completely made up and blatantly false answers, with no viable proof to its claim. Other than it says so. But then again, it could be right :) fact check the fact checking fact checkers checking facts 5 times fast :)

As much as I’d like to use an inflation sack, it seems like such an unnecessary luxury to me. Space of movement for me inside a 1 person tent is limited, even with a spacious 1 person tent. Need the space to inflate this sack and pad. Not going to do it outside. Usually under heavy bug pressure, so after dinner tasks are done in the tent. Also, hard for me to justify spending $40 on a bag that I potentially find more useless than full.  Then again, every time on trail I think, dang, I should buy one and try it out. Hopeless

[Matt Dirksen]

I liked the video but as Stephen mentioned, he didn’t address the volumetric difference between warm air and cold air, in my recollection, there could be a 15-20 percent reduction in volume (depending RH and altitude). I’m pretty sure an air mattress losing 15 percent of its volume will impact its thickness, especially where it is compressed the most (since one’s body does not compress the mattress evenly.)

 

[jscott]

I blow up my pad just after setting up my tent, so that I can lay out my sleeping bag. This is in the afternoon. (Many through hikers have a different habit.) Just before going to bed…ummm, pad…I usually put a few more puffs or a schnozzle full of air to plump it up again. almost always this is good enough. I think my body warmth helps keep the pad warm and inflated. I also use a thin light pad beneath my sleep pad for protection, mostly. But it adds a few degrees of insulation too.

[Jerry Adams]

I’ve noticed that before

I’ll blow it up with warm air, then in an hour it’ll be deflated a little.

So I’ll put another breath in

[Jerry Adams]

“Where he’s headed with this”??????

Good one

[Jerry Adams]

Same here Todd, I’ve had a large amount of condensation after a night of breathing

I can’t think of a time when I’ve breathed inside my bag that it made anything wet.  Because I never breath inside my bag

Hmmm… maybe an experiment to try

That is the type of old timers advice that is sometimes wrong

[Todd T]

I can’t think of a time when I’ve breathed inside my bag that it made anything wet. Because I never breath inside my bag

I can attest that it’s possible to do it by accident.  I used to be a deeper sleeper than I am now.

[Terran Terran]

A couple breathes in your bag can warm it up. I don’t sleep that way. Conditions may vary. Perhaps it turns a 20* bag into a 22* bag and makes a difference overall. Perhaps in extreme situations. I’m usually not testing it to its limits. Rules are not laws. While often there is a reason, they have exceptions. Do what works for you at the time. Heed the warnings, but be adaptable.
Sometimes my base layer is my midlayer. Yes. I went there.

[Terran Terran]

Put a raft in the cold water, it will always deflate.

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