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How does the insulation in a Therm-a-Rest NeoAir Work?

Therm-a-Rest NeoAir Insulation
Therm-a-Rest NeoAir Insulation

Have you ever wondered how the insulation in a NeoAir works? It’s surprisingly simple.

All Therm-a-Rest NeoAir air mattresses have the same honeycombed air baffles, shown in the photo above. These run from one side of the air mattress to the other, unlike many other manufacturer’s sleeping pads where the baffles run lengthwise.

Therm-a-Rest adjusts the insulation power or R-value of each pad in its NeoAir product line by adding a metallic reflective coating to the inside of the baffles: the more baffle surfaces that are covered, the higher the R-value of the pad. See Sleeping Pad R-Values.

ModelSizeR-ValueWeight (oz)Width (in)Length (in)Thickness (in)
NeoAir XThermRegular5.71520722.5
Neoair XthermLarge5.72225722.5
NeoAir All SeasonMedium4.91820662.5
NeoAir All SeasonRegular4.91920722.5
NeoAir All SeasonLarge4.92525772.5
Womens NeoAir XliteRegular3.91120662.5
NeoAir XliteSmall3.2820472.5
NeoAir XliteRegular3.21220722.5
NeoAir XliteLarge3.21620772.5
NeoAir TrekkerTorso21620472.5
NeoAir TrekkerRegular21925722.5
NeoAir TrekkerLarge22625772.5

Think about it this way: when you lie on a NeoAir sleeping pad, your body heat warms the air inside the mattress baffles. The metallic coating helps reflect that heat back at your back and helps regulate the rate in which the trapped heat is radiated out of the pad and back into the air surrounding you.

Therm-a-rest also adjusts the rate of radiation loss by using different exterior fabrics on their sleeping pads, letting them dial-in different R-Values for different customer preferences and uses.

Pretty clever, huh?


  1. Good Post!

    Note that just air has an R value of about 1 per inch. A regular Neoair does not get any boost due to the internal baffeling. It isn’t small enough to prevent convectional losses. The metalic film, a lot like mylar, doesnt seem to help that much because your body only looses about 8-12% (likely towards the low end) because of wearing wearing clothing or long johns in a bag. R value does not see any real boost from air pocket isolation till it gets much smaller than that used in the NeoAirs.

    As part of a sleeping system, no one ever considers that a smooth surface pad will also compress the insulation of your bag. Nor do they measure *where* heat bleeds out of most pads. Example: The XFrame allows the bag to loft between compresion points, soo, they don’t say an R value because their pad doesn’t have more than an R1 or R1.5, but, the bag lofting between framing easily adds another point to the R value while sleeping. As far as I know Klymit is the only one doing this, though there are ceartainly other possibilities with built in framing on inflateables.

  2. The pic of the baffles is great! That is kind of what I had pictured in my head they would look like. It’s always neat to see how things work. Any idea when the xtherm is coming out and the price?

    • I’m not sure when the XTherm is coming out. They just announced it at Outdoor Retailer last month, so I would assume it won’t be out until this spring or summer. My guess is that pricing will be around $150.

      The Xlite is replacing the NeoAir classic, so this is the time to buy a Classic if you want a good deal on the old mattress, which is perfectly sufficient for 3 season use.

      • To anyone reading this in 2021, Therm-a-Rest are claiming an R value of 6.9 !
        I don’t understand how this works. Radiant body heat (infra red) doesn’t pass through clothing and sleeping bag insulation without being absorbed and converted to conducted and converted heat, neither of which can be reflected. The air pockets in the mylar matrix aren’t small enough or plentiful enough to effectively trap converted heat and mylar is an excellent conductor, so by all logic this pad should not be nearly as warm as claimed. What’s going on??

  3. Ya, I figured after the OR show eBay would explode with the classic neo airs. As of yesterday though it hadn’t.

  4. I have a regular Classic and my grandson uses a small Classic. We’ve never been cold on those and have spent several nights at 17°F while camping with them. Although I’m completely satisfied with what I’ve got, the XTherm will probably burn a hole in my pocket someday.

    • We’re both sleeping on the newer XLite models now. The interior welds in the small one failed on a hot day in the Wichita Mountains of Oklahoma. I put the pad outside for a couple minutes as I was striking the tent and kept hearing muffled explosions, which I took to be from the nearby Fort Sill artillery range. When I turned around, the small one was a giant balloon. My regular developed a leak that I couldn’t find, even when dunking the pad in the tub. Therm-a-Rest replaced both pads free of charge with the newer model. In my opinion, the newer ones appear to be tougher and quieter.

  5. lists the XTherm …. for $189.95 … says it’s backordered though.

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