How can I increase my pad’s warmth

[Cal]

Looking for a simple way to increase the warmth of my sleeping pad. Don’t want to buy another if possible. I’ve got an Exped synmat that’s got a decent cold rating. I went out this past winter and it got down to 15. I’d brought a length of reflectix bubble material that I set the pad on in the shelter. It still got a little cold, not bad but not comfy. Should the reflectix have been on top of the pad? Also, I’ve got one of those emergency reflective Bivvy sacks that I was thinking I could slip the pad into and then sleep on top of but idk if that would work. Anyone know anything about this? Thx

[David Thomas]

Reflecting infrared works best the warmer an object is.  So your warm body on Reflectix (i.e. use of a quilt) would make more difference than Reflectix under a sleeping bag which in turns makes more difference than the Reflectix being under the pad.  Also, reflecting IR functions across an air gap.  If it is touch, it just conducts heat.  So IR barriers either need a rigid air gap (better yet a vacuum like a Thermos bottle) or to be on top so they are not compressed.

I suspect the Reflectix did almost exactly as much as a similar thickness of bubble-wrap would have.  i.e. it helped, but the shiny aspect didn’t make much difference.

The classic 3-season solution is to put 1/8″ CCF pad under your inflatable pad.  And if that’s not enough in winter, then step it up to a Z-lite under your inflatable (if you already have a high R-value inflatable, which you do with an R of 4.9).

Putting the pad in a bivy would help a bit, but again, where you need it most (hips, shoulders), it will be compressed against the pad and ground, so you won’t get an air film on each side of the fabric – just a very thin fabric pressed tight to the stuff top and bottom.

Putting the pad AND YOURSELF and bag in the bivy would make a pretty big difference, and I find that works for one night at a time, if I can air out the bag/quilt of the moisture it’s absorbed.  If not, you’ll wet out your bag more and more each night in the bivy.

[Cal]

Dave, thank you. Very helpful!

[Mark Verber]

slight variance of dave’s suggestion… put you inside the bivy, and the pads and bag outside. That way moisture doesn’t accumulate in your insulation… e.g. it’s a vapor barrier which I find starts to be useful when it’s <15-20F.  This will boast your warmth, but not help significantly feeling the cold from below.  That said, when I am toasty, the cool from below is nice.  At home I pay for that privilege (chilipad).

–mark

 

[Edward John M]

I used a Synmat until it deglued and became useless, I found it not very warm at all if it was soft enough to be comfortable. So I suggest as an experiment blowing it up a bit harder and seeing if it will make a difference. I now use a S2S Comfort Plus and put up with the extra weight in exchange for the comfort and warmth. I also use a thin foam and plastic pad but that is mainly to protect my investment

[Mark Fowler]

When experimenting with pot cozies I found 3mm closed cell foam is under half the weight of reflectix and has the same insulating power – assuming these items are similar to what I can get in Australia.

[bradmacmt]

The classic 3-season solution is to put 1/8″ CCF pad under your inflatable pad.

Only caveat, the CC goes on top

[David Gardner]

Gossamer Gear has the 19″ x 59″ Thinlite 1/8″ CCF pad for $18 and it only weighs 2.5 ounces

[Paul S]

Hi Brad, You mentioned “Only caveat, the CC goes on top.”

Could you elaborate on that? I have read that R-values are additive. Let’s say you have two pads, R=3 (inflatable) and R=1 (closed cell).

3+1=4, and 1+3 also = 4, right?

So, what difference does order make?

[jscott]

Get an exped downmat…7.8 rating.

I use the GG thinlite to partially protect my normal summer exped from possible pucture. It adds a tiny amount of warmth; not much at all. Doesn’t claim to, I think.

[Ben H.]

I agree a simple analysis says it shouldn’t matter which is on top but I have heard quite a bit anecdotal evidence that putting the ccf on top is better.  I think a big part is when you lay on a thick air mattress quite a bit of heat is put into the mattress establishing the thermal gradient…. you have to warm up the mattress.  Putting the ccf on top buffers you a bit from that initial cooling of your body.

[jscott]

There was a long discussion on where to place an insulating pad some years ago. My intuition is that you want to protect the mattress from the source of the cold; i.e. the ground. So put the pad under the mattress. Others gave convincing reasons for placing the insulating pad on top.

I don’t know. glad to help!

I do like adding any protection from punctures, so pad on the ground is good for that. But on snow, this isn’t an issue.

[David Gardner]

From Gossamer Gear’s website:

“If you own an ultralight backpacking air mattress, then it should be an indispensable part of your kit – an air mattress alone might slip and slide and leave you freezing from convective heat loss. Place a Thinlight foam insulation pad on top of or underneath your air mattress to prevent sliding and provide insulation.”

Who knows? I’m ordering a GG Thinlight pad anyway, so I’ll try it both ways and report back.

[J R]

In terms of warmth:  air pad alone  <  CCF on bottom  <  CCF on top.

In terms of comfort:  air pad alone  =  CCF on bottom  >  CCF on top.

[Paul S]

JR. “In terms of warmth:  air pad alone  <  CCF on bottom  <  CCF on top.”

How come? In terms of insulation value, R value is R value.  And Gossamer gears mention of convection: R-value measurements include those effects since air currents would obviously reduce the measured R-value.

If someone can explain this scientifically I’d love to hear about.

 

Thanks all!

[Edward John M]

Perhaps perceived or initial warmth perception?

[Eric Blumensaadt]

Lay your “day clothes” under your mattress, especially the torso area. It does help.

Collect dry leaves to spread in a 6″ thick layer under your tent floor. Or, non-LNT, unobtrusively cut evergreen boughs for the same purpose.

[jscott]

“unobtrusively cut evergreen boughs for the same purpose.”

and then lay a pad under your mattress to stop the boughs from puncturing your mattress AND a ground sheet between the boughs and the tent floor to keep the sap from sticking on the same.

Eric, this is so Ray Jardine! and probably a bad idea. How do thousands of backpackers unobtrusively cut boughs from trees?

[Edward John M]

Are there thousands of backpackers in the Northern Boreal where the fir trees grow.
Probably not a good idea in crowded places down South of the Canadian border tho.

[bradmacmt]

https://backpackinglight.com/forums/topic/56634/

A good read from the wayback machine.

I’ve used CC pads on top of inflatables and underneath. While not empirical, I’ve found on top warmer in practice. At the end of the day, isn’t that what really counts over theory?

I’m not an engineer and don’t play one on TV, but my reasoning why the inflatable feels warmer with the closed cell pad on top is this:

The ground is NOT as cold as the air surrounding an inflatable, and the ground warms and holds warmth when on it, even with a pad on top, due to body heat penetrating it. The air around the pad is colder than the ground and holds almost no warmth. That same air is vying for access to the interior of the pad, from the top and from the sides, not just the ground side. It seems more cold air is entering the air mattress from the exposed areas on the top and sides of the inflatable than the bottom.

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