Pad on top or bottom!
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wiiawiwb wiiawiwb
(wiiawiwb) - F
Pad on top or bottom? on 11/15/2013 19:38:17 MST Print View

I have a RR Solar that I will use with a DownMat. I've read conflicting suggestion about whether the RR Solar should be used on top or underneath the DownMat.

In one thread, it was suggested to use it below an air mattress to stop conductive heat loss. Other threads people have recommended using it on top.

1) What is the correct way, the RR Solar on top or below the air mattress?

2) I've seen several Youtube videos where people put the RR Solar inside their sleeping bag. Is that a good idea?

Edited by wiiawiwb on 11/15/2013 22:06:02 MST.

jerry adams
(retiredjerry) - MLife

Locale: Oregon and Washington
Re: Pad on top or bottom! on 11/15/2013 19:57:24 MST Print View

I put my pad inside my sleeping bag, but

There is an air space on each side of you, just on top of the pad, that allows drafts

In a way, it's better to have the sleeping bag against you all the way around

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
re on 11/15/2013 21:12:41 MST Print View

Below:

its more comfy, protects from thorns getting to air mat. R-value diffrence (if any) is negligible imho.

Roger Dodger
(RogerDodger) - F

Locale: Wess Siide
Re: Pad on top or bottom! on 11/15/2013 21:29:04 MST Print View

not saying it's the best and only right way, but here is my reasoning:

RR or Z-lite (or blue foam) on the bottom, to protect the air pad, and act as a barrier.

air pad in the middle, about 75% inflated, because then the cushion gives comfort.

sleeping bag on top.

ok now to eat my words:
some sleeping bags such as Big Agnes, have an empty sleeve on the bottom and no insulation. product description: "Underside insulation has been eliminated and replaced with a sleeve for a Big Agnes 20 in. wide rectangular pad (sold separately)"

those are designed to slide a pad in the sleeve.

Now to eat my words again:
I own Ridgerest, and Z lite and Exped air pad. if it's one summer night, I'll take my chances with the air pad only, if it deflates I'll complain but I'll be ok. For winter I'll pair the z-lite with the air pad.

for snow and multi nights, RR on the bottom, Air pad middle, sleeping bag on top

Edited by RogerDodger on 11/15/2013 21:31:11 MST.

Matt Dirksen
(NamelessWay) - MLife

Locale: Mid Atlantic
Re: Pad on top or bottom! on 11/15/2013 21:30:44 MST Print View

Personally, I always prefer the firmer, more durable pad under an air mattress; to reduce the possibility of damage to my air mattress, and because it feels more comfy - to me.

However (technically speaking) the shiny surface of the RR Solar will only provide an aid to your "R" value if it is pretty much against your skin or perhaps inside the sleeping bag with you where your radiant heat can be reflected back onto you. The shiny surface won't do much to resist conductive or convective heat loss, the primary way we become cold while in a sleeping bag.

In my opinion the "increased R value" of any reflective stuff is more marketing glam than anything else. (Fwiw, the FTC is finally getting their act together, at least in the building industry: http://www.greenbuildingadvisor.com/blogs/dept/energy-solutions/ftc-cracking-down-false-r-value-claims )

Matt

Chad Poindexter
(Stick) - F

Locale: Wet & Humid Southeast....
CCF on top IME on 11/15/2013 21:48:50 MST Print View

In my personal experience, I found that I was warmer with my 1/8" Thinlight pad layered on top of my NeoAir. And this was a noticeable difference.

I cowboy camped. The ambient temps were about 16-17 F, not sure about the ground temp. There was no snow on the ground, and the ground was not wet, however, at night the leaves and anything on the ground had a layer of frost on them.

As I said, I used a GG 1/8" Thinlight pad at full size, and a regular size original NeoAir. I was also using my Marmot Helium sleeping bag.

I started the night out with the ccf under the Neo. When I laid down, I immediately felt cold beneath me, however, I assumed that this was because everything was cold. I hoped that as I laid there my body warmth would heat it all up, and all would be good. An hour later I was not so sure.

I was still noticeably cold beneath me when I got up to pee (and to get some blood pumping and try to warm up. Before laying back down I put the ccf pad on top of the Neo. As soon as I laid down I could tell a difference. I was warm again. However, for these conditions, the original Neo and the 1.8" ccf pad was at it's limits. I noticed that if I moved around much I would feel a little cold under me for a moment, but it quickly warmed back up once I got settled back in.

So, for me, ccf on top = warmer; ccf on bottom = more protection for air pad. So, if I happen to be carrying both, how I layer them depends on the condition.

There are other threads about this on this forum, among others, and reading through them you will find that some like it better one way while others the other way. My suggestion is to take it all out, try it for yourself and see what you like best...

Dustin Short
(upalachango) - MLife
Re: CCF on top IME on 11/15/2013 23:59:45 MST Print View

We have this weird simplistic view that R-Value is additive but rates rarely are, especially when dealing with complex thermodynamics.

The simple way of stating it is that CCF more efficient at insulating than air. So it takes more energy to push heat through a CCF than it does through an air mat (convection sort of requires you to heat up an entire air mat at once while conduction in a CCF allows more local effects to take place).

This is because the different R-values and insulation properties have greater effects in different phases of heat loss. That's not very intuitive. Let a bullet represent our heat output (we want to slow the speed of the bullet) and different materials represent insulators. Imagine air and steel are our two insulators. If we shoot a bullet through 100 yards of air and 1/8" of steel, the bullet will (ideally) lose the same amount of energy regardless of what order we place the air and steel in relation to the gun barrel. The bullet however behaves dramatically differently based on the order. If the bullet penetrates the steel first, most of the energy is dissipated right at the bullet source (ie the energy is kept near the source). If the bullet encounters air first, it travels a great distance before dissipating energy when it hits the steel plate.

Similarly think of traffic jams on a freeway. We want a jam (represents extra warmth/insulating value). So which seems slower to you in your immediate perception as you drive, a traffic jam right as you enter the freeway or at the very end as you try to exit? As you enter, even if the overall traffic is identical. Your body thinks the same way.

"Warmth" is as much a physical function of heat transfer as it is perception. A ccf causes a local buildup of warmth next to our skin which increases our perceived temperature before it is "eventually" lost to the environment. With the ccf on the bottom we pump all of our heat into the air mat first where it freely flows (which in a 3d world is also less efficient due to heat loss from the sides as well). Makes most sense to keep the heat as close to the body as possible as quickly as possible (an underlying reason for why VBLs work so effectively too at increasing temperatures).

That said, CCF on the bottom protects the air mat from damage which if you factor in the low R-value of a flat pad evens out in the long run. So unless you have a nice cushy bed of snow, it tends to make more pragmatic sense to put the ccf on the bottom. If snowy, your pad is safer and the cold is usually enough to warrant the extra warmth.

wiiawiwb wiiawiwb
(wiiawiwb) - F
Lean-to on 11/16/2013 07:15:20 MST Print View

In my case, almost all of my colder-weather hiking will end up at a lean-to where I'll stay for the evening/weekend. So my pad will be on a controlled, flat surface. If I understand you correctly, that argues for placing the CCF on top or even in the sleeping bag.

I would be using a .2mil exterior-window plastic to place below the Exped DownMat to help prevent contact with any burrs or other sharp items.

Ian Schumann
(freeradical) - M

Locale: Central TX
Re: top or bottom on 11/16/2013 09:21:29 MST Print View

I'm with Dustin on this, at least from a purely best-insulation perspective.
Caveat: as others have pointed out, there is a substantial benefit to placing the CCF under the air pad -- you get an added layer of protection / insurance against your air pad going flat. That's certainly something to consider.

But to answer your question from purely a warmth perspective ... and phrasing it a bit more simplistically than Dustin ...

Consider the problem in the same way as you'd consider insulating your body with clothes, such as a puffy jacket, or in the same way as a sleeping bag surrounds your body. In the BPL community I think we're a little more familiar with the scientific perspective on that issue because of the detailed articles that have been published here over the years covering that topic.

The primary idea with insulating garments / sleeping bags is that you create a cavity of air around your body. The body pumps heat into that air mass, slowly raising the average temperature. Hopefully the layer of insulation that is directly outside that air mass is doing its job and preventing the air mass from losing that heat to the outside world -- that would be by preventing radiative, convective, conductive, and sometimes evaporative heat loss.

Most critically now, consider this: hopefully the air mass around your body is not so large that your body struggles to heat it up efficiently. This is why it's important that our sleeping bags are cut trim enough that there isn't a bunch of extra unused air space inside the bag with you -- that would make you COLD even if the bag was good otherwise. The same is true for puffy jackets -- even if the seal is good at the cuffs and the hem, if your jacket is sized way too large for you, you'll feel noticeably colder inside, because the internal air mass that you're heating up is larger than it otherwise would be.

Make sense so far?

Now then ... consider an air pad. For the sake of demonstration we'll consider a purely air-filled pad such as a Big Agnes Air Core or that kind of thing. Basically this is a large, shaped, plastic ziploc bag full of air. It has almost no insulative value, because the air inside the pad is free to move around, rather than being kept still. If we were to consider an analog to an air pad in the clothing world, it would be something like a pool floaty -- a plastic inflatable jacket-like thing, filled with nothing but air.

Conversely, consider a CCF pad. Very different! A CCF pad also has tiny air pockets in it, but since those pockets are CLOSED (CCF) the air is held very still, and the insulative value-per-thickness is much higher than with an air pad. To what can we compare a CCF pad if we want to find an analog in the clothing world? My best guess would be like a thin neoprene wetsuit.

Finally ... let's consider that if we had an all-inflatable jacket, made of the pool toy kind of material, and we also had an all-neoprene jacket, made of wetsuit material ... how would we want to layer these? For the sake of experimentation, let's assume that (somehow) the fit for these two garments is the same ... regardless of how we layer them, they will fit properly.
So do you put the neoprene on the inside or the outside?
For anyone that's ever put on a wetsuit before, the answer is pretty easy. Putting closed cell foam next to your skin makes you VERY WARM, very quickly. That's because the air mass trapped next to your skin is minimal, so it takes almost no time for your body to raise the temperature of that air mass.

By contrast, if you were to put the pool toy jacket on the bottom, next to your skin ... your body would be heating up 1" or 2" of surrounding freely-moving air space, quite a bit more than what was trapped by the wetsuit. It would take much longer to feel warm in that getup, because it would be so much less efficient for your body to heat that larger air mass.



Whew ... this post grew long quickly. Anyway, I think I've gotten the idea across. Having CCF next to your skin should feel noticeably warmer, and faster.

Edited by freeradical on 11/16/2013 09:22:24 MST.

wiiawiwb wiiawiwb
(wiiawiwb) - F
Wow... on 11/16/2013 10:01:58 MST Print View

Thanks everyone. It is heartwarming to digitally rub elbows with so many insightful people. We all have our strengths and it's quite something to be able help others and, in turn, be helped by others.

You're the best!!

jeffrey armbruster
(book) - M

Locale: Northern California
"Pad on top or bottom!" on 11/17/2013 13:55:24 MST Print View

It seems to me that having the pad on the bottom cuts/stops the warmth from your inflatable pad from conducting to the ground. Also, having a thinsulite on top of your inflatable prevents your body warmth from warming said inflatable. So with the pad on the top wouldn't you end up with an inflatable at basically ground temperature--cold--and a thin insulite on top of that; versus the thinsulite on the ground and an inflatable slowly warming from your body temperature.

In any case, protecting my inflatable is the most important thing for me, so the thinsulite goes on the ground.

I appreciate that actual science may trump my intuitive analysis.

Edited by book on 11/17/2013 20:18:15 MST.

Stephen Parks
(sdparks) - M

Locale: Southwest
Re: Pad on top or bottom? on 11/17/2013 18:37:26 MST Print View

Very timely for me as I was just wondering the same thing, just having bought a 1/8" pad to go with my UL7. One other possible advantage (though I haven't tested it yet) to having a ccf pad on the bottom is it might keep the air pad from sliding around.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
clear cut pad on bottom on 11/17/2013 19:03:35 MST Print View

Its super obvious that a ccf should go under the inflatable. Even if there is ONE reason for it to go on top that will not outweigh all the benifits for it going on bottom.

Desert Dweller
(Drusilla)

Locale: Wild Wild West
Pad top or bottom? how bout both? on 11/17/2013 19:18:06 MST Print View

How about making an envelope (short, like torso length) of 1/8 CCF and inserting the pad, and sleeping on top of that? Then you have to protection of the CCF on top and bottom. :-)

And E
(LunchANDYnner) - M

Locale: Pacific Northwest
Pad sammich on 11/17/2013 19:26:30 MST Print View

Ooooh, the Sleeping pad Sammich, or rather, the Sleeping pad Pita Pocket!
If you use a 1/8" one, that would be a good option without adding all that much weight.

Lawson's pads would've been great for that since his pads came pretty wide (which i cut down to 20" wide for myself), but sadly, he's out of stock, and probably won't be making anymore.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
lawson on 11/17/2013 19:43:51 MST Print View

Why do you say he wont make any more? I cant imagine he makes much money selling these products for so cheap + free shipping.

And E
(LunchANDYnner) - M

Locale: Pacific Northwest
No more Insulite pads per Email update from lawson on 11/17/2013 20:53:50 MST Print View

Lawson stated in an email update to subscribers:

"After the foam pads and grills are gone, they will not be re-stocked. I have decided to focus my attention moving forward on cord, tent stakes and shelters."

Desert Dweller
(Drusilla)

Locale: Wild Wild West
Thin pad on 11/18/2013 09:14:46 MST Print View

GG thinnest works perfect, so light a '"pocket" would work dandy.

jeffrey armbruster
(book) - M

Locale: Northern California
"Pad on top or bottom!" on 11/18/2013 10:13:06 MST Print View

Wouldn't a pad on top prevent your body heat from warming the inflatable?

Edited by book on 11/18/2013 10:13:52 MST.

John S.
(jshann) - F
Re: Pad on top or bottom? on 11/18/2013 13:34:16 MST Print View

I like it on the bottom.