Pad on top or bottom!
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Misfit Mystic
(cooldrip)

Locale: "Grand Canyon of the East"
RE: Clear cut pad on bottom on 11/18/2013 14:02:39 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"

Ryan, and possibly Roger, have spoken quite compellingly on this subject before on the site; I believe it may be in an article. The conclusion: from a thermodynamic performance perspective, using a ccf on TOP of an inflatable, even an insulated inflatable, provides significantly better performance. The reasons have been related by posters above, Ryan's comments reflected the actual application of thermodynamic principles to the question.

That being said, there are very good reasons for using the ccf on the bottom that have nothing to do with thermodynamic performance.

Chad Poindexter
(Stick) - F

Locale: Wet & Humid Southeast....
Re: RE: Clear cut pad on bottom on 11/18/2013 21:11:50 MST Print View

"The conclusion: from a thermodynamic performance perspective, using a ccf on TOP of an inflatable, even an insulated inflatable, provides significantly better performance"

^^^^^^

I totally agree with this, and realized it through experimentation... and I also agree that it was significant...

As far as using the ccf pad under the air pad, so long as you clear the ground of anything sharp, this should not be an issue. But, if it is not cold enough to need that extra warmth, then under the air pad is a good option.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
science says warmer on top, but... on 11/18/2013 21:37:20 MST Print View

Okay so it's warmer if the CCF is on top, point taken.

Thats one reason (its warmer) but it still doesnt outweigh all the benifits of the CCF going on bottom.

I guess if you are pushing the limits of your sleep system so much that having the pad on top will help you get through the night, then try it out.

CCF Pad on bottom PRO's:

1. Comfort
2. Pad wont slide around as much, ccf is sticky.
3. protects from thorns

Franco Darioli
(Franco) - M

Locale: Melbourne
Pad on top or bottom! on 11/18/2013 21:52:19 MST Print View

Call me crazy but this is how I would solve the problem.
I happen to be rich enough to have a floor at home for my exclusive use.
So, in my case, I would turn off that air conditioning system (well it is already off...) put the two mats down on on top of the other, get my sleeping bag out and sleep on it.
The next night I would reverse the order of the two mats.
After a few nights I will end up with enough in house information to make my own mind up.
But yes , I am a bit odd....

jeffrey armbruster
(book) - M

Locale: Northern California
"Pad on top or bottom!" on 11/19/2013 10:37:10 MST Print View

Over the years (!) I've read enough commentary on this topic by knowledgeable people to assume that the pad on top is the warmest way to go. But I still would like to know: don't you end up with a very much colder inflatable this way?

With no ccf pad under an inflatable, the inflatable will trend towards ground temperature through convection--cold. This is especially true if you put a ccf pad on top of the inflatable, since this will block any body heat from entering the inflatable.

But with the ccf under the inflatable to block convection loss, and a warm body on top warming the inflatable, especially a downmat, it would seem intuitively that you'd have a warmer set up.

Edited by book on 11/19/2013 19:01:08 MST.

Larry De La Briandais
(Hitech) - F

Locale: SF Bay Area
Re: "Pad on top or bottom!" on 11/19/2013 11:50:32 MST Print View

"don't you end up with a very much colder inflatable this way?"

I am sure you do, and that is the point. The inflatable provides a large area to loose heat from. The less heat you pump unto it from your body the less you will loose.

jeffrey armbruster
(book) - M

Locale: Northern California
"Pad on top or bottom!" on 11/19/2013 13:31:09 MST Print View

Except that, with my old Exped downmat, using a thinsulite underneath, the pad would actually warm ME up--I would often unzip my bag and use it like a quilt, with the downmat staying warm underneath me.

Granted, I'm talking about three season use, but I often used this downmat to below freezing (with my bag zippered up) and felt that it stayed warm.

I thought that the whole idea of a downmat was to keep you warm; or at least, retain heat. If not, why pay for the down?

I may be missing something here...

Edited by book on 11/19/2013 15:15:42 MST.

Larry De La Briandais
(Hitech) - F

Locale: SF Bay Area
Insulation (such as down) on 11/19/2013 14:51:26 MST Print View

Insulation NEVER warms you up. There is no exothermic reaction within insulation. It's purpose is to "trap" heat, to keep it from transferring from one side of the insulation to the other. When we use it to keep us warm we are attempting to keep too much of our body heat from away from us. We are "trapping" our own body heat next to us.

Franco Darioli
(Franco) - M

Locale: Melbourne
Pad on top or bottom! on 11/19/2013 15:52:40 MST Print View

Insulation NEVER warms you up

Yes technically correct HOWEVER on the practical side I understand and agree with what Jeffrey is saying mostly because I have a DM and know how it works for me when I use it as opposed to when I think about it in front of my computer...

jeffrey armbruster
(book) - M

Locale: Northern California
"Pad on top or bottom!" on 11/19/2013 16:24:20 MST Print View

All right fine it doesn't warm me up. But my downmat is a far sight warmer than other inflatables that I've used. But I doubt that it would be if I had a blue mat on top of it. It seems that a blue mat on top would make all inflatables equal,in terms of warmth. So again, why pay for the down?

Edited by book on 11/19/2013 22:50:36 MST.

Larry De La Briandais
(Hitech) - F

Locale: SF Bay Area
On top or bottom... on 11/19/2013 17:07:01 MST Print View

You want whichever is more insulating next to you. If the down mat is more insulating than the foam pad then that is what you want on top to keep you the warmest. Many of the air mats (non-down ones at least) are not very insulating and therefore you want them on the bottom.

Based on a quick google search the OP's pad appears to have an R value of 3.5 while the Exped Downmat has an R value of 8. Therefore, the pad belongs on the bottom for that combination. That gives the best thermal performance and protection for the Downmat. :)

Edited by Hitech on 11/19/2013 17:14:01 MST.

Franco Darioli
(Franco) - M

Locale: Melbourne
Pad on top or bottom! on 11/19/2013 17:14:23 MST Print View

WWWWW (the OP) has a DM XP9, R8

Misfit Mystic
(cooldrip)

Locale: "Grand Canyon of the East"
RE: Pad on top or bottom! on 11/19/2013 17:26:07 MST Print View

OK, here's a simplified explanation as far as I understand it. I make no claims of being as eloquent or educated as Drs. Jordan and Caffin. as I understand it:

An insulated, inflatable pad's primary contribution to insulation is through the prevention of heat loss through radiation. The best means for this is thick insulation to trap air and limit it's movement. Down is quite efficient for it's weight for this purpose. Notice I said limit air movement rather than prevent. There is still air moving within the down, due to the temperature gradient between the top and bottom of the pad, and this is carrying heat away from your body through convection. This convection is greatly mitigated by the down in the pad, but it is not completely eliminated.

By placing a layer of ccf between your body and the pad, these air currents can no longer come in contact with your body surface. This does not eliminate the insulative capabilities of the down in the inflatable. The thin layer of ccf will fail to retain enough body heat in cold conditions, thus the down provides for further insulative loft; the purpose for inflating the pad is to preserve this loft beneath the pressure of your body weight. Without any insulation value in the inflatable, the ccf probably won't be enough. It seems a couple of members tried using BA Clearview pads with ccfs a few years ago with poor results.

This may differ regarding the XTherm, as it uses very different principles to provide insulation.

wiiawiwb wiiawiwb
(wiiawiwb) - F
Oh boy.... on 11/19/2013 20:04:09 MST Print View

....now I don't know whether I'm afoot or horseback.

Both sides have provided convincing arguments, both scientific and practical, why the above method vs. the below method is preferred.

We've come full circle.

michael levi
(M.L) - F

Locale: W-Never Eat Soggy (W)affles
on top is warmer on 11/19/2013 20:29:20 MST Print View

What about the neoair xtherm? It uses reflectors instead of insulation like the microfiber of a exped synmat.

Tad Englund
(bestbuilder) - F - MLife

Locale: Pacific Northwest
Re: Pad on top or bottom? on 11/19/2013 21:20:46 MST Print View

After trying many different pads and combination of pads and what combination of pads go on top or bottom; even without a PHd I came to the conclusion the the CCF is better on top:
1. Technically it is, as stated above.
2. More important- for me, it is far more comfortable on top. A pad on top fills in the "rolls" or voids in the inflatable and makes for a smoother, more like my bed at home feel. And thus, I'm more comfortble and if I'm more comfortable, I am warmer (inside and out). It may be all in my head, but that is all my body needs to be warmer; or the tought of such.
I think it, thus I am.
Tad