Camp Mat R-Value Guide and Adding Up Two Mats12 Mats Calculated from Official Numbers

A guide to camp mat R-values, in makers' wording: 2.0 to 2.8 is three seasons, 4.5 covers part of winter, 5.4 is all seasons and 8.5 is harsh winter. My pick for the one on the bottom is the Ridge Rest Classic, and for winter with a single mat, the NEMO Eclipse All-Season. When you stack two, you add the two R-values as is.

A mat's R-value is not set by thickness: a 7cm air pad loses to 2.5cm of foam

mont-bell's U.L. Air Pad 180 is 7cm thick with an R-value of 1.4. mont-bell's own Foam Pad 25 180 is 2.5cm thick with an R-value of 2.3.

The thicker one loses. Read a mat's warmth by R-value, not thickness. R-value is a number for how hard it is for heat to pass; the larger it is, the less heat escapes to the ground.

How I chose

The first thing I confirmed was how it was measured: whether the R-value is a number from the shared standard ASTM F3340. Next I divided weight and price by R-value and re-lined up the 12 mats.

Their strengths split clearly. For weight efficiency, the top air mats; for price efficiency, closed-cell (foam mats with sealed bubbles). Since R-values add, I made my pick a mat to lay underneath for people who own an air mat, and a mat that reaches winter on one for people who have nothing.

R-value guide: lined up by season in the makers' words

My reading: 2 to 3 from spring to autumn, 4 in the season when frost falls, and 5 or more on snow or in midwinter. The boundaries are lines I drew from the makers' words. If in doubt, choose the higher.

Stacking two mats, adding R-values is enough

You can add them. R-values can be added, and an air mat on a closed-cell mat is an example. A closed-cell mat has no valve for air and does not break by getting a hole and going flat overnight, so the one on the bottom should be closed-cell.

Quick table of R-values for 12 camp mats, and price per point

Scroll the table sideways →

Dividing weight by R-value too, the R8.5 Tensor Extreme Conditions is 55.5g per point and the R1.4 U.L. Air Pad is 360g, a gap of about 6.5x. Weight efficiency gets better the higher the air mat's R-value.

Calculating the total R-value of two stacked mats

Comparing 1 mat, the X Therm NXT at R7.3, with the mont-bell combination at a total of R7.2, the price is JPY 15,740 lower and the weight 551g heavier. For people who carry by car, stacking is the better deal.

The one on the bottom: my pick is the Ridge Rest Classic

The deciding point is JPY 3,575 per R-value point, the lowest of the 12. It adds the same R2.0 as the Z Lite Sol or Switchback for the least money. This part is a weak point. It rolls up, so it packs into a 51 × 20cm tube. It suits people with a three-season air mat who carry by car.

If you prefer folding, the Z Lite Sol: It folds like a screen, packing to 51 × 13 × 14cm. Aluminum is vapor-deposited on the surface, and Therm-a-Rest explains that this makes it 20% better at insulation than a model without it. The price is higher than the Ridge Rest. It is the one for people who take it out and put it away at every break.

If you match everything with NEMO, the Switchback: At 2.3cm it is the thickest of the three, and it pitches use even in harsh winter “stacked with another three-season mat.” The weak point is weight: 415g, the heaviest of the three. It suits people whose upper mat is also NEMO.

One mat through winter: my pick is the NEMO Eclipse All-Season

The deciding point is price. At R6.2, its price per R-value point is the lowest among the air mats. The price is below any of the two-mat combinations above, so for someone buying a first mat it comes cheaper than stacking. The weakness is weight: 60g more than NEMO's own Tensor All-Season. It is the mat for people who want the sleeping feel of 10cm thickness.

If you want lightness, the Tensor All-Season: 400g at R5.4. It delivers the insulation pitched as “safe to use in all seasons” with a lighter body than the Eclipse. Watch the price: JPY 6,111 per R-value point, higher than the Eclipse. It suits people who want to cut what they carry on their back.

If three seasons are your focus, the XLite NXT: 370g is the lightest among air mats of R4 or more. The weak point is price: JPY 9,044 per R-value point. It suits people who put lightness first and add a closed-cell mat underneath to reach R6.5 in the middle of winter.

How R-value is measured

The principle is simple. According to an article on Sea to Summit's UK official site, a mat is sandwiched between a warm plate and a cold plate, and the electric power used to keep the warm plate at 35°C is measured. A mat that needs less power is losing less heat, so its R-value is higher. Therm-a-Rest, NEMO and mont-bell write the name ASTM F3340 on their official pages, so numbers can be lined up across makers.

Things to watch

There is a caution on inflating. In freezing cold, moisture from your breath may freeze inside, so avoid blowing it up by mouth. An air mat loses air if it gets a hole, so take the included repair kit or a patch.

Who is it for?

It suits people who want to stop the cold from the ground from autumn into winter. For the one underneath, the Ridge Rest Classic (R2.0); for winter on one mat, the Eclipse All-Season. When you stack two, you can add the R-values as is.

If it is only the warm lowlands of summer, three seasons at R2.0 to 2.8 is enough. If you already own R5 or more, you can also start by reviewing the difference between comfort and limit temperature in sleeping bags. If you cut every gram for mountaineering, there is also a single top-grade air mat.

FAQ

Gear in this article

Ads & images: Rakuten Ichiba

Therm-a-Rest Ridge Rest ClassicTherm-a-Rest Z Lite SolNEMO Switchback RegularNEMO Eclipse All-SeasonNEMO Tensor All-SeasonTherm-a-Rest NeoAir XLite NXT

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