Up until now, comparing the warmth level of sleeping pads across the market has been a bit of an apples to oranges game. Even if a brand lists the R-value of their sleeping pad, the testing behind that number is totally different than the testing from another brand. To get around this problem, the industry agreed to adopt the new ASTM R-value testing standard so that you can better compare between sleeping pads of all brands. And rumor has it that just like sleeping bags, both REI and MEC will require all pads sold to adopt the new rating system.
So what does the R-value rating mean exactly? In short, it’s a measure of how well a layer of insulation — in this case your sleeping pad — resists the conductive flow of heat or your body heat being lost to the ground. In general, an R-value of 1 to 2 is good for summer, 2-4 makes a great 3-season pad, 4-6 is an all-season sleeping pad, and anything above 6 is for the extreme cold. Keep in mind that variables like humidity, type of shelter, ground conditions, and personal preference might mean you go higher or lower.
Similar to the EN/ISO ratings for sleeping bags, the ASTM R-value standard requires a specific machine to do the testing and rigorous testing criteria in order to calculate an approved R-value rating. This ensures that the outcome is comparable across all brands.
Therm-a-Rest was one of the first brands to invest in the testing machine and now all their sleeping pads will adhere to the ASTM R-value rating standard. As a result, a few of their pads in the current lineup have adjusted R-value ratings, including the NeoAir Uberlite that went from 2 to 2.3, the NeoAir Xlite that went from 3.2 to 4.2, and the NeoAir XTherm from 5.7 to 7.2.
With the push to roll out the ASTM R-value rating system across all sleeping pad in the market by Spring 2020, you can expect to be able to better comparison shop by next year.