When you’re shopping for a new camping or backpacking sleeping pad, it’s tempting to assume that a thick, cushy one is going to keep you warmer than a thinner one. But advanced designs and types of insulation mean this isn’t necessarily the case. You need a reliable way to know how well a pad will insulate you against conductive heat loss when making your buying choice.
What Does R-Value Mean and How Does It Help You Choose a Sleeping Pad?
The good news? Many top brands use a specification called “R-value” to provide customers with a measure of how well a sleeping pad resists (the “R” in the name of the spec) heat loss. The not so good news—until recently—is that there was no standard for how manufacturers arrived at that measurement, so buyers couldn’t reliably compare one sleeping pad’s R-value with another’s.
That changed in 2020. Now we have an R-value test standard for the very first time. Brands can use a single test method (ASTM FF3340, to be precise) to assign R-values. That means that major brands that offered only an estimated temperature rating in the past now must provide an R-value. The goal is to help consumers make an apples-to-apples comparison.
The new test standard has been in the works for several years. A coalition of major brands, including REI Co-op, Therm-a-Rest and many others, sought to come up with a standard that was accurate and could be used by any sleeping pad maker. For a look at how testing is done under the ASTM FF3340 standard, check out this R-value testing video from REI Co-op’s Magnusson Test Lab.
The Transition Period
From the 2020 model year on, REI Co-op will only carry new pads if they have an R-value that was determined by the new test method. Keep in mind that if you’re heading out to buy a new sleeping pad tomorrow, you might find a handful of pads on the shelves that don’t have an R-value from the new standard. Soon, though, older inventories will be sold and newer models will take over. The co-op projects that by late summer all pads on REI.com and in REI stores will be in compliance.
One bright spot for bargain hunters: Some previous-generation pads will be sold at discounted prices. That’s a nice windfall for your gear budget—and a possible tipoff that the pad might have an R-value spec that was assigned just prior to the testing changeover. It’s worth noting, too, that the new test didn’t induce dramatic technology innovations in the industry, and that many pads tested out to have similar R-values under the new test. Some tested lower and others higher, but no notable trends emerged.
The Sleep System: How Sleeping Bags and Pads Work Together
Your sleeping bag and pad—your sleep system—work in tandem to maintain your warmth. The sleeping bag industry went through a standardization process many years ago in order to produce the sleeping bag temperature ratings you see today. (For a glimpse at how temperature ratings are done, check out this sleeping bag testing video from REI Co-op’s Magnusson Test Lab.)
Having standardized tests now for both your bag and your pad make it possible to develop a more comprehensive way to predict your nighttime warmth. REI’s lab team has been crunching the numbers and has distilled this new data to create a helpful snapshot of how sleep systems work:
Sleep Systems: What Sleeping Pad and Sleeping Bag Rating Should I Get?
|Expected Nighttime Low||50°F||32°F||20°F||0°F|
|Pad: R-Value Range||Under 2||2 – 3.9||4 – 5.4||5.5+|
|Bag: Temperature Rating||30°F or lower||20°F or lower||15°F or lower||0°F or lower|
This new sleep system data suggests that it’s worth looking at a more-insulated pad if you want your bag to live up to its temperature rating. For more details, check out the sleep system section of How to Choose a Sleeping Pad or How to Choose a Sleeping Bag.
How Do You Know If a Pad Has the “New” R-Value?
Until all the older models are off the market, you’ll have to do a little extra sleuthing to figure out whether or not a pad’s R-value reflects the new standard. Look closely at the following sources for clues:
- Packaging, including things like hangtags or stuff sacks
- Product info on brand websites
- Product info on retailer websites
The key phrase to look for is “ASTM” (or “ASTM FF3340”) next to an R-value, which tells you it came from the new test. Unfortunately, because of logistical challenges of updating a high volume of information quickly, you might need to check multiple sources for a while.