New Standardized R-Value: NEMO’s Involvement in and Approach to ASTM F3340

Article by NEMO

New Standardized R-Value: NEMO’s Involvement in and Approach to ASTM F3340

Read on to learn What Is R-Value, Why It Matters, and How to Pick the Right One... Plus, pro-tips for building the best four-season sleep system.

After 8 years of leading the charge for standardized R-Value testing, NEMO helped to develop an industry-wide standard that allows consumers to accurately compare pads and understand their warmth. Photo by Jason Hummel.

Choosing the best gear for your adventure requires a solid understanding of the whats, whys, and hows behind each product. Things might not always go according to plan, but when it comes to staying warm (or cool), dry, supported, and safe from the elements, you’ll want to know that the few precious items you brought along will get the job done. So, if you’re the kind of gear head who loves to nerd out on the little things, then you’ve come to the right place — and if you’re not, then you’re also in good hands.

Because, here at NEMO, we’re keen on being detail-oriented in the name of great design. Getting down to the studs is our thing, it’s an approach that we’re proud to stand behind — and are always willing to champion for the betterment of all. That’s why you’ll notice something new for 2020 on our product descriptions, packaging, and messaging. It’s not just the launch of our new first-of-a-kind hybrid pad or our dialed-in sleep systems and adventure kits that’ll catch your eye, but the standardized ASTM R-Values of our pads will stand out, too.

In an effort to provide greater clarity and a better understanding of how to choose the best sleeping pads and bags in all four seasons, the NEMO team collaborated in an industry-wide initiative to redefine the R-Value specifications for all. In short, we helped to develop the standard and make this the most simple, repeatable, streamlined, and precise testing process yet.

The test works by measuring how much energy it takes to keep the hot plate at body temperature. The result is R-Value as a measurement of one-directional heat flowing from a warm body through a pad to the cold surface beneath the pad.

What is R-Value

R-Value is shorthand for thermal resistance, which is a measurement that reports how much a sleeping pad resists or prevents heat from flowing from a warm body and down to the ground. Until now, there has not been an industry-wide, standardized measurement for every outdoor brand or retailer to accurately test or measure R-Value. It’s likely that you’ve heard it before, but now this testing procedure has undergone the research and development to ensure that it’s reliable and consistent across the board.

Now, instead of recommended temperature ranges of the past, R-Value can help inform purchase decisions with advantages of confidently comparing any R-Value to another and the ability to calculate the precise, additive R-Value of multiple pads stacked in use (such as an air pad on a closed-cell foam pad). Lastly, R-Value is an insulation factor — it will never change and it remains independent of environmental factors and person sleep temperatures.

So, the next time you see an R-Value rating accompanied by ASTM F3340 — in the description of a NEMO sleeping pad and elsewhere — you’ll know you’re getting the best and most accurate measurement possible. R-Value targets inform our dogged pursuit of new materials and experimentation with new construction techniques, in order to provide folks with balanced options throughout our sleeping pad line that best fit with their requirements for warmth, weight, packed size, comfort, and activity.

NEMO Tensor™ Alpine uses 3 layers of metalized film suspended in its support baffles for silent insulation that results in an R-Value of 4.8.

How to Pick the Right R-Value

Whether you’re stuffing your pack or adding to your cart, we made the process of choosing the right R-Value as simple as possible. You don’t need to be a mathlete or even burly pirate to demystify the R-Value of a sleeping pad. No matter how chilly it gets, not you nor any of your camping companions will have to shiver their timbers during a long and cold night ever again.

Here’s the breakdown: The lower the temperature, choose a higher R-Value. The higher the temperature, choose a lower R-Value.

This simple formula works well because it all relates back to the relationship between you and the ground.

“The human body constantly generates heat. If you can’t transfer that heat someplace then you will eventually overheat. Conversely, if you lose too much heat, you will eventually become hypothermic,” says NEMO’s Director of Engineering, Pat McCluskey.

“In very warm weather, it is best to choose a low R-Value pad so that you can dump more heat to the surrounding environment. In very cold weather, it is best to choose a high R-Value pad to limit the amount of heat leaving your body.”

Obviously, those are not the only two factors contributing to how hot or cold you are while sleeping outside. Temperature, humidity levels, and the materials of your clothes all contribute as well. Yet, R-Value is our best tool to gauge how much insulation you need your sleeping pad to provide for every adventure in every season.

Here are a few more tips from our product gurus, Spar and Pat, to help you maximize your sleep system all year long.

  • Clothes are layers, too. Spar suggests thinking big picture. “Consider your entire sleep system — sleeping bag, sleeping pad, and what could be worn while sleeping — as a modular system. How you choose to combine base layers, mid-layers, a beanie, and socks allows you to effectively extend the temperature range (whether that’s a higher or lower temperature) of your sleep system.

  • Stack those layers from top to bottom. “Sleeping bags are more suited to insulating your top surface because the insulation is allowed to loft and perform as intended,” points out Pat. “The insulation on the bottom surface of a sleeping bag is crushed under the weight of the sleeper, significantly limiting the effectiveness of the insulation.” He recommends taking into account the effectiveness of your top and bottom layers.

    “Sleeping pads are most suited to insulating your bottom surface. Sleeping pads have structure to support body weight and allow the internal insulation to remain lofted and effective. The result is that on a cold night, even with a very warm bag, you can still be cold if your pad is not warm enough because while the heat is not allowed to escape through the top surface it can still short-circuit through the bottom surface.”

R-Value is additive, which means that you can use two pads and add their R-Values together. Temperature ratings cannot accommodate this.

Why It Matters

For us, it has been important to wait to publish these ratings until there was a standardized R-Value test measurement that allowed consumers to fairly and accurately compare sleeping pad warmth options within and across brands. Historically, NEMO has not published R-Values because we believed there was not enough rigor in the test methodology that informs these very important criteria specific to each customer’s buying decision.

Working on a committee with other industry partners, NEMO played a leading role in developing the new ASTM test standard that was ratified in Fall 2019. With this standard in place and all of our pads tested to this standard, we are now publishing all of our R-Values.

We feel strongly that these steps meaningfully align with our mission — to create great experiences in the outdoors for those with the will and imagination to seek adventure — through simplifying the decision-making process and getting people into the proper, most comfortable gear possible.


Explore the complete NEMO sleeping pad line to discover the different R-values to better understand the types of adventures they are designed for.