Better Understanding XLite NXT and Xtherm NXT – Year Round Use

[Taylor Z]

Hey Everyone,

I’m trying to determine the best pad for me to get through the entire year (really don’t want to own two pads understand that may just be the case though). I’m in Ontario, Canada and get outside year round so that puts me into hot summers (30C / 86F) and relatively cold winter nights (-25C / -13F). Important to note that the extreme of either end is of course rare and short lived. Winter usually is not that cold and summer rarely that hot. Regardless of which pad, in the winter months a closed cell foam pad (zrest) will always come along to supplement the air pad.

Trying to understand if the Xtherm NXT or XLite NXT would be the best fit. Generally a normal to slightly hotter sleeper. In the winter I have a mummy bag (FF Ibis) and a alpha direct overbag, Summer-Fall I’m looking to switch to a quilt this year from a three season mummy. I get I should understand therma capture more but would an Xtherm sleep warmer than the XLite in the warmer months. Basically all things being equal if its hot and I’m lying on top of this thing sweating will it be better/worse/same?

Pro and Cons we already know:

XLite NXT:

Lighter

Simpler design (easier to roll and pack, in my experience)

More Quiet

More affordable

Xtherm NXT:

Warmer

70D Bottom more robust

Would a XLite be considered enough when used with the foam in the winter ? I’m just so stuck with this silly decision and I respect the heck of the Backpacking Light community and feel you can get me sorted ;)

Thanks for all your help !!! You all rock

[dirtbag]

Im a hot sleeper and I have both the Xlite nxt and the Xtherm ( not nxt ) ( yet).. because!!  I think it would be possible to get away using the regular Xlite NXT with the closed cell Z rest in way below freezing temperatures.  You could also get something cheap and lightweight like a 1/8 ccf pad from MLD or Gossamer Gear for more insurance if u wanted too, but that may not be necessary.  Take what I am saying with a huge grain of salt, like I said,  I have both style pads.. but if I could only afford 1, it would probably be the new Xlite NXT regular/wide rectangle version.. to use all year round.

[dirtbag]

Ps.. try it out.. if it doesnt work for you, you could always sell it and pick up the X-Therm..

[John Vance]

I sleep on an xtherm year round.  I have used the xlite with 1/4 foam in the winter with excellent results as well.  I like redundancy for winter in which case the xlite plus foam may be the more versatile setup.

[Taylor Z]

Thanks for your insight, for colder climates a zrest comes with always ride too as insurance, seat, etc so I would always have that under me to so that encouraging to hear :)

[Taylor Z]

Thanks John ! Do you feel the Xtherm is toasty in the summer or totally the same if you would have the XLite under you ?

[John Vance]

Most of my summer trips have nighttime temps in the 60’s or colder.   My hot trips are usually on desert sand and I just use a 1/4″ pad or lay on the cool sand.   I don’t find the xtherm too warm.

What I feel makes pads uncomfortable is the non breathable nature of the material.  At home I sleep on a memory foam mattress that is 14″ thick in a 70f house.  I’d estimate r value at least 14.  But it breathes and that makes a difference. I use a quilt and sleep in long lightweight base layers which helps a lot.

[Taylor Z]

Thanks for the info John. Yes, I suspect that certainly helps for sure, I’d likely find myself in slightly warmer temps but that’s great to know that you find it cozy :)

Now I’m not super on top of the book smarts here so forgive me ;) but these pads (XLite + Xtherm) compared to our beds at home insulate differently. The nearly one foot foam beds we all have now is generally trying to let our heat escape due to the fact that is has little/nothing to do to allow us to be comfortable (not super cold in most bedrooms). It’s a massive piece of foam though and obviously insulates well and if tested would yield a sky high r value. So breathability is paramount in mattresses and all the newest tech for home mattresses is trying to do the opposite of what the camping pads are doing which is release heat. The Neoair pads are essentially actively trying to trap our bodies waste heat and reflect it back up to us while simultaniously trapping and bouncing cold air from below. The Xtherm simply has more of this going on which adds a touch of bulk and added complexity to the inside of the pad. Now that I’ve done a poor job explaining, wouldn’t a Xtherm if it was actually hot out sleep hotter than a Xlite ? In that is more efficient and capable at trapping my bodies heat and of course the non breathable material.

Thanks for the feedback team :)

[David P]

I suspect the Xtherm wouldn’t feel hotter on a warm summer night than the Xlite. There are plenty of nerdy variables that factor into our perception of thermal comfort, so I’ll take a stab at the few I’m familiar with. In cold weather, a pad is mostly helping us stay warm by reducing heat loss to the ground by conduction.  I figure convection and evaporation would play little to no role in terms of heat loss to the ground for these pads (although an air mattress with no insulation would probably have small convection currents within the empty air space, which can increase heat loss to the ground). Most pads don’t prevent heat loss by radiation, but the reflective film in these two pads would be effective effect on that front. Without knowing more, I suspect the differences in heat loss from radiation are fairly small in comparison between the two pads, and I’m assuming it’s the added insulation in the Xtherm that accounts for the difference in the r-value by reducing conduction.

Borrowing from building science, heat loss from conduction is the product of the surface area times the u-value (which is the inverse of the r-value) and the “delta T,” the difference in temperature between the two materials, such as your body and the ground. On a moderately cold night, if there is a 50 degree F difference between your body and the ground, the heat flow across a 20″ x 72″ Xlite pad, R 4.5, would be 111 Btu per sq ft per hour deg F. The heat flow across an Xtherm, R 7.3, would be 68 Btu/(sf hr deg F).

But on a warm night, if the ground is just 5 degrees cooler than your body, the heat flow across the Xlite would be 11 Btu/(sf hr deg F) and across the Xtherm would be 6.8 (Btu…) which is a pretty negligible difference and a pretty minimal amount of heat flow. If the ground and your body are the same temp, the heat transfer between the two should be zero. Since the surfaces of both pads are impermeable, there’s no difference in their behavior as far as ventilation, evaporation, etc. and I suspect the heat transfer horizontally to or from the surrounding air is fairly minimal in summer time.

Since I haven’t used either pad in hot conditions I can’t speak from experience, but I have used a thick standard thermarest on plenty of warm and hot summer nights without noticing any impact of the pad on thermal comfort. I think the ambient air temperature, humidity, air movement, and whatever clothing or sleeping bag/ quilt/ sheet is on top of you will play a much bigger role in your perception of comfort. Hope that helps shine some light from one direction, at least.

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