Are wide sleeping pads “colder”?

[GR]

I have seen discussions on reddit as to this effect. For example, if trying to decide between a Thermarest Xtherm NXT regular (20″) vs wide (25″), is it fair to say the wide one will feel colder?

I have seen comments about how your body (whose size is constant) will need to expend more energy to warm and maintain the heat in wide pad (more volume to warm up). As well, the baffles seem to be connected, so if more pad is wider, more of the pad will be exposed to cold air on the sides where your body isn’t covering it, that cold air can travel along the baffle and bring down the temperature in your sleeping pad.

Any truth to this? Wondering what experiences anybody has.

[Dennis W]

Very subjective observation . . . I’ve used both Xtherms, wide and regular and haven’t noticed a difference. I have felt cold when my arm or elbow slips off the narrower pad onto the ground or cold, which does tend to wake me up. That rarely happens with the wide pad. BTW, this was in below zero Fahrenheit temps.

 

[MJ H]

Maybe because the regular width pad forces you to keep your arms close to your body, it feels warmer?

[Jason]

I’ve experienced that, but it’s VERY pad specific.  For example, no issues on a 25″ Nemo Tensor or Exped 3R, but felt like I was sleeping on ice when on a 25″ wide Ether Light.  It has a similar R value to their thinner “ultralight” pad, which I’ve used in winter and been just fine (21″ width though).

[Bill in Roswell]

Yes, very pad dependent. I speculate that is why the Big Agnes Zoom UL feels colder than its R value would indicate. Exped, Nemo, Thermarest seem to be spot-on R value. Ive not tried StS as a 3″ thick pad works for me.

[GR]

I roll around a lot. I wonder if some are more prone to having air flow around inside. Like if you roll over, does cold air from the edges get pushed/mixed into the centre? I would feel like horizontal baffles might be more prone to this. I think they are often a single air chamber the whole width of the pad.

[HkNewman]

Big Agnes Zoom UL … Exped, Nemo, Thermarest

Wonder how much materials and construction play a role?  Thermarest air pads, except Uberlite last I checked, especially have a reflective heat barrier that will simply return heat.  All pads will have some heat loss but the bigger companies have probably put some [proprietary] effort into combatting it.  The only way may be thermal imagery over a colder temperature range (where humidity and wind effects are nullified .. even caloric intake that day).   These pads use body heat, so that’s measurable.

There’s also design.  In the extreme, the latest Swedish army impermeable covered foam pad has “wings” on each side cut to rise when body weight is applied to the pad’s center – may be for marshy bivouacs, but I can see an application for quilt users in colder temps.  Especially with metallized surfaces or even pad innards as heat is reflected to the lower sides (then there’s perception, being less drafty, et ..) The Swedish foam pad is over 2 lbs however…

[Todd T]

Probably temperature dependent too.  A wider pad has more surface area exposed to the air temperature, so if the air is colder than the ground it could (partially) counter the benefit of more protection from the ground.

[GR]

It could very well be temperature dependant. One of the issues with the ASTM R-value test is they do the testing in a room that is “warm”. I recall being surprised when I heard it, something like 20C or 70F. Maybe somebody knows the exact room temperature they test at.

It would probably be better to test at freezing temperature.

[Jerry Adams]

If the tube of an air matt was open, you would get air currents inside carrying heat from underneath you to the side where it would be cold

If the tube was full of foam, then this wouldn’t happen

it makes sense this would depend on the construction of the sleeping pad

[Author]

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