Stacking sleeping pads

[soumodeler]

When using 2 sleeping pads during cold weather, does the order matter? Inflatable on top of foam, highest r value on bottom, etc? My foam pad is smaller than the inflatable, so my first thought was to place it on the bottom, both for comfort and for protection of the inflatable.

[nsherry61]

This has been discussed extensively on this site. There are arguments both ways. However, for maximum warmth you want the closed cell pad on top and the inflatable on the bottom. It's not super noticeable until it's getting cold enough to stress the system. But, in really cold weather, the difference and improvement with the closed cell pad on top is substantial!

[DownEaster]

The thicker inflatable has more surface exposed to the air, on the sides. Place the pad which is going to lose more heat further away from your body.

[Leo L.]

In really cold conditions, CCF on top is the way to go, for double reason if the CCF has a reflective surface.
A third reason might be, that if camping in open snow, pieces of snow don't get that easily stuck between the two mats if the bigger sized CCF is on top.

[cmoulder]

This has been discussed extensively on this site. There are arguments both ways. However, for maximum warmth you want the closed cell pad on top and the inflatable on the bottom. It's not super noticeable until it's getting cold enough to stress the system. But, in really cold weather, the difference and improvement with the closed cell pad on top is substantial!

+100

I have personally tested this a few times and CCF on top is the clear winner. I also concur that if you don't notice a difference it simply isn't cold enough.

It also matters what's under the air mat. Ice/snow is a giant heat sink, as is frozen ground with a lot of water content. Dry vegetation such as leaves provides some insulation and changes the equation. In an emergency, the decidedly non-LNT practice of using evergreen boughs could actually be a life saver.

For me, a plain ol' 3/8" EVA mat with an Xtherm max works fine down to about -10°F, and below that a RidgeRest is required. (Full length for all.)

[wordstew]

How about throwing a car windshield sun protector or some relectix on top of an air pad

[Cheyou]

How about stacking a xterm short with a Klymit ultralight V it’s r4.4

[russb]

It does also depend on the type of inflatable. The xtherm mitigates loss of heat via radiation, so should be on top of ccf. Any other inflatable mitigating loss via conduction should be under ccf.

[Leo L.]

And then, if the CCF is a thick and stiff one, the more reason to put it on top - due to spreading the pressure on the inflatable a bit thus preventing it from getting locally compressed.

We should write down a whole matrix of cases, conditions and solutions.

[soumodeler]

I have an XTherm max and a z rest ccf. So put the XTherm on top?

[Leo L.]

I have an XTherm max and a z rest ccf. So put the XTherm on top?

The reflective one on top, if both are reflective, the CCF on top.

[jjozgrunt]

Is there a need if you have a mat with a R value of 5?

[DownEaster]

Is there a need if you have a mat with a R value of 5?

R-5 is the baseline used to establish EN (European Norm) temperature ratings for sleeping bags. If your bag isn't adequate to the actual temperature you encounter, you need more insulation. That could come from a second sleeping bag, a quilt, a bag liner, a bivvy sack, extra clothing, or a second sleeping pad.

[cmoulder]

Is there a need if you have a mat with a R value of 5?

At -25°C, yes.

[Leo L.]

It depends on several factors, especially personal ones.
When I was (much) younger I slept on a single sheet of plastic, in lack of any CCF.
Later I slept fine on a double CCF at -20°C.
Nowadays I'm using the same double CCF and a Prolite Plus as soon as the temps drop below -10°C, and I find it very uncomfortable if the matress is not adequate. I can help myself if the bag is on its limit, but really hate any cold coming up from the ground.
(If this is the only constraint that comes with age, thats OK for me)

[nsherry61]

It does also depend on the type of inflatable. The xtherm mitigates loss of heat via radiation, so should be on top of ccf. Any other inflatable mitigating loss via conduction should be under ccf.

This is a reoccurring statement that doesn't make a lot of sense to me, and I suspect is speculation and NOT reality. The IR-reflectivity can only increase heat retention by somewhere around 5-10%. So, although it may contribute to the effective insulation an X-therm and X-Lite pads, I don't think it can account for as much as the hype suggests, and is minor compared to the effectiveness of the internal baffling system they use.

Secondly, if one is using a reflective CCF pad like a RidgeRest Sol or a Z-Rest Sol, then the IR reflectivity is already taken care of by the CCF and the IR reflectivity of the X-Therm or X-Lite being on top is irrelevant, whereas the loss of heat through the sides of the inflatable (if that is truly why the inflatable on bottom works so much better) is still relevant.

[Leo L.]

Reflection does no additional good if there is tight contact to the heat source at the same time. It works best if there is a small distance (air gap) between source and reflective surface - something in the reality of hiking is hard to achieve.
Also, reflection has much better effect if the temperature difference is high, the reason why the reflective surface should be as close to the body as possible. But even done in an optimized way, the gain by reflection is not all that high.

I think the good insulation effect of, say, an X-Lite is mainly due to their finely sub-divided baffles which minimizes convection inside the baffles.

[russb]

This is a reoccurring statement that doesn't make a lot of sense to me, and I suspect is speculation and NOT reality. The IR-reflectivity can only increase heat retention by somewhere around 5-10%. So, although it may contribute to the effective insulation an X-therm and X-Lite pads, I don't think it can account for as much as the hype suggests, and is minor compared to the effectiveness of the internal baffling system they use.

Secondly, if one is using a reflective CCF pad like a RidgeRest Sol or a Z-Rest Sol, then the IR reflectivity is already taken care of by the CCF and the IR reflectivity of the X-Therm or X-Lite being on top is irrelevant, whereas the loss of heat through the sides of the inflatable (if that is truly why the inflatable on bottom works so much better) is still relevant.

I suppose my speculation is only confirmed by my extensive use in sub-zero temps. This in addition to using the combination in lean-tos with raised floors thus also meaning the lean-to floor would equal the ambient air temp. The reflective nature of the xtherm is maximized by the fact it is an inflatable thus providing the distance between the mylar and the body.

[Deadeye]

I prefer CCF on the bottom for comfort and to prolong the life of the inflatable. I've used this order in the minus 20 degree range, and never tested the other way around.

[rocketsocks]

CCF on top, it has smaller voids to heat up as long as it’s covered by the bag, but roll around and you have to reheat the little dimples again.