I had no idea what R-values were before my first thru-hike. I used a Therm-a-Rest Z-lite for a late-season John Muir Trail trek, because I heard that’s what a lot of thru-hikers used.
It was late September, and the nighttime lows were deep in the 20s. Though I still finished the trail, I averaged 2-3 hours of sleep per night. By the time I reached Whitney, large boulders off the side of the trail started to look like animals, or my personal belongings.
Post-trail, I knew immediately I needed to invest in a better sleeping pad. I learned about R-values, and now my pad is one of my favorite pieces of gear.
R-values: An Overview
R-value is a standard term that defines how well a product or material insulates heat. It’s used in construction, when comparing different woods or other building materials — higher R-values insulate the home better, which in turn helps with climate control.
Translated into backpacking terms, the higher the R-value of your sleeping pad, the harder it is for heat to escape, meaning you will stay warmer.
R-values are used to measure sleeping pads because of the way our bodies lose and generate heat. A sleeping pad with a low R-value means that your body heat is moving more quickly through the pad and into the ground. Conversely, higher R-values trap your body heat and transfer it back up to you.
In sum, the lower the nighttime temperatures while camping or backpacking, the higher your R-value should be. Picking the wrong R-value can set you up for some miserable night's sleep!
What R-value Should You Choose?
Lower R-values from 1-2.5 provide minimal insulation and are best reserved for truly warm weather backpacking trips where weight is more important than warmth. Popular sleeping pads in this category are closed-cell foam pads (Z-pads) and ultralight air pads.
This middle range of insulation is better for longer treks where temperatures vary, or “chilly” weather trips. The exact R-value you choose will depend on how cold of a climate you’ll be in, how warm your sleeping bag/quilt is, and how warm or cold of a sleeper you are. For example, on a fall trip in the Utah desert, I might bring an air pad with an R-value of around 3.0, whereas on a fall trip into the high alpine Wasatch, I would go with a pad closer to 4.0.
For below-freezing temperatures and/or sleeping in the snow, a warm sleeping pad is way more of a priority than saving weight. Insulated sleeping pads are a great option for cold weather camping, as is stacking two pads on top of each other. Many backpackers will use a closed-cell foam pad underneath an air pad to up their warmth. You can also select a self-inflating air sleeping pad with a higher insulation value, but these are significantly heavier.
*When using multiple sleeping pads, simply add the two R-values together to determine the total insulation of your sleep system.*When in doubt, opt for a higher R-value pad.
What style of sleeping pad to choose?
Closed-cell foam (CCF) pad: These mattresses fold up accordion-style (or roll up) and require very little maintenance. There’s no risk of the pad popping, you can use it as a seat, and they’re extremely lightweight and inexpensive. However, CCF pads are quite bulky and require a good strapping system on the outside of a pack. Additionally, they only provide enough insulation for warmer trips. Popular options: Therm-a-Rest Z-Lite, NEMO Switchback, and the Gossamer Gear ThinLight.
Air pad: A true air mattress requires you to inflate it, by mouth or with a pump sack. They are extremely lightweight and packable, but more susceptible to popping. Air pads come in a variety of insulation values and baffle designs. Popular options: Therm-A-Rest NeoAir XLite, NEMO Tensor, and Klymit Static V2.
Self-inflating pad: A self-inflating pad does just that; you lay it out and it inflates on its own. The built-in extra insulation in these types of pads provides warmth and a bit of extra protection against popping. Also, if it does pop/ deflate, you still have a small layer of cushion, while an air pad leaves you right against the ground. However, self-inflating pads are also heavier and bulkier than an ultralight air pad.
My sleeping pad is the one piece of my backpacking kit where I consistently prioritize warmth/ comfort over weight. I’ve spent one too many nights tossing and turning, as my heat is siphoned into the ground, to continue to skimp on the insulation power of my sleeping pad.
With an understanding of how R-values work, you’ll be able to pick the perfect sleeping pad for you next overnight in the backcountry, maximizing your time spent in R&R and REM!
Katie is a freelance writer based in Salt Lake City, Utah. When she's not behind her laptop, you can find her guzzling instant coffee in the backcountry or developing a new and expensive outdoor hobby. To see her adventures and occasional long rambles, follow her on Instagram @katelyn_ali