learning to sleep on a UL mat

[icefest]

Here is my train of thought:

Ignoring R-value of less than 4.5. (I use it in winter too)
You get this table: (sorted by weight in g of LW, and R value)


At this point Xtherm is the lightest by 140g (cf Downmat UL 7)



You will remember that I also mentioned toughness. Here I decided top use denier as ballistic/tear stength isn't supplied by either company. This is for the bottom layer which I'm more likely to likely to puncture on a rock etc. (if need be I can flip it in the snow.)
The Exped UL mats are 20 denier. The normal Exped maps are 75 denier. Neoair are 70 denier on bottom.
The UL mats were decided to be less tough.

When I exclude the UL mats I get:

Compared to the Downmat 7, the Xtherm is 540g lighter. (520g lighter than the Sunmat 7 @ R4.9)


Here is the full comparison: http://puu.sh/4tAW7.png This has direct weight/insulation ratios.
Any errors feel free to correct me.

[Orion]

Ironically, it turns out I'd need a UL mat so large that it would be heavier than my non-UL mat.

But likely 10x more comfortable..

A large UL mat may be more comfortable but there's no way it's ten times. I have a car camping "Luxury" Thermarest that is 63x196x5 cm, comparable to the larger UL mats. It's definately more comfortable than my short Prolite Plus but not by that much really. Even my bed at home isn't ten times more comfortable.

I sleep perfectly well on the Prolite Plus. I'm happy with it. I'd go with a lighter mat provided it were no less comfortable.


It's interesting to read that there are more than just a few people who dislike the NeoAir. That's news to me.

[icefest]

I think a lot over people forget that convection mainly transfers heat up or across (assuming a density decrease with increased temperature). Assuming you don't move much in your sleep, the air in the mat should stratify and make radiation the main form of heat transfer.
Air is a pretty crap conductor of heat.
This just leaves radiation, where the best insulator is a reflective surface tuned to a certain black body radiation (infrared in this case).

Down is great against all three forms of heat transfer, but not as good as a silvered surface at preventing radiation. It's just overkill in a sleeping mat.

Maybe Thermarest have a patent on this tech, but I'd have no problem buying an Exped if they made them like this. They do make them cheaper.
At least, that's what my limited understandings of thermodynamics tell me. Feel free to correct my mistakes.

[Joomy]

Here is my train of thought:

Ignoring R-value of less than 4.5. (I use it in winter too)

I guess if you narrow your parameters to 4.5+ R value and high-denier fabrics then yes, the X-therm is the obvious choice. But I and many others use 3-season mats in winter by supplementing them with thin CCF mats. And by thin I mean between 3 and 5mm thin. This seems to work well, although why exactly it does is not entirely clear since a 3-4mm CCF mat only has an R-value of around .75 maximum, but it does provide 4-season warmth.

I think a lot over people forget that convection mainly transfers heat up or across (assuming a density decrease with increased temperature). Assuming you don't move much in your sleep, the air in the mat should stratify and make radiation the main form of heat transfer.
Air is a pretty crap conductor of heat.
This just leaves radiation, where the best insulator is a reflective surface tuned to a certain black body radiation (infrared in this case).

Down is great against all three forms of heat transfer, but not as good as a silvered surface at preventing radiation. It's just overkill in a sleeping mat.

Maybe Thermarest have a patent on this tech, but I'd have no problem buying an Exped if they made them like this. They do make them cheaper.
At least, that's what my limited understandings of thermodynamics tell me. Feel free to correct my mistakes.

I think your assumption that a block of air should act as an insulating layer is flawed. In theory you might think that hot air should rise and stay at the top, but in practice this doesn't happen at all. Not sure exactly why, I'm guessing it's at least partly because your body doesn't heat the mat evenly, but circulating currents definitely do form which suck your body heat away and transfer it to the ground. Either way, that's the whole point behind down or synthetic insulation or the mini-baffles in the NeoAir mattresses -- they limit the amount of air circulation, and therefore limits heat transfer by convection.

[Strider]

Yes for outright insulative capability and fabric strength, the Xtherm comes out on top.

BUT, you are missing the most important criterion of all - comfort. Not all gear purchases can be made purely based on specs.

[Orion]

...I and many others use 3-season mats in winter by supplementing them with thin CCF mats. And by thin I mean between 3 and 5mm thin. This seems to work well, although why exactly it does is not entirely clear since a 3-4mm CCF mat only has an R-value of around .75 maximum, but it does provide 4-season warmth.

That makes sense. Many 3-season mats are already pretty warm. For example a NeoAir XLite is R 3.2 so adding another .7 to that puts you in 4-season range. I use a Prolite Plus (3.8) by itself on the winter snow.