When it comes to sleeping outdoors, the insulation level of your sleeping pad is one of the most important factors there is in determining your comfort. But many consumers aren鈥檛 aware of the need for sleeping-pad insulation, most don鈥檛 know how much insulation they need, and no one has the ability to compare the insulation of one pad to another. All that鈥檚 about to change, as REI and its Canadian equivalent,听MEC, will begin requiring the brands they carry to report a standardized R-value rating in 2020.听
R-value is a measure of how well something resists the conductive flow of heat. The higher the number, the better it is at insulating you from the cold. So听if you鈥檙e going camping, it鈥檚 an important number to know. Without insulation below you, the cold ground will zap听the heat out of your body as you sleep. And your body compresses the insulation in the portion of the sleeping bag you lie听on, meaning it鈥檚 the pad that provides the key insulation beneath your body.听
Did you know that, in order to achieve its advertised temperature rating, your sleeping bag needs to be used in conjunction with a 4.0 R-value pad?听I didn鈥檛, at least not till I hopped on the phone with Greg Dean and Brandon Bowers from Therm-a-Rest鈥檚 design team.听For some perspective, the brand's ultra popular, ultralight pad, 听only ranks a听3.2. You likely need a higher R-value pad than you're currently using just to get the most out of your sleeping bag.
鈥淭he R-value measurement is very pure,鈥 Dean says. You鈥檒l see some brands list the insulation abilities of their pads in temperature ratings or even applicable seasons. But none of these metrics give you a听hard number detailing听just how good at insulating your听pad really is.
Trouble is, many sleeping-pad makers don鈥檛 currently release this information (if they even test for it), and no one uses a standardized methodology so you can accurately compare one brand鈥檚 R-values with听the next. You cannot currently shop for which sleeping pad best meets your needs听without actually testing all of them. Heck, I鈥檝e听done that, and I can鈥檛 even offer you a precise assessment of their warmth.听
This obviously creates a glaring need, and it鈥檚 one REI and MEC set out to address by creating an industry-wide working group to develop a unified test methodology back in 2016. After nearly three years of work, that standard was . The new methodology will enable various sleeping-pad makers to test in identical conditions听and release like-for-like numbers that consumers will be able to use to cross-shop. Just like you can can compare performance and fuel economy across multiple cars, this new standard will, for the first time, allow you to compare the insulation levels of sleeping pads, in addition to their thickness and weight.听
To determine the R-value of a sleeping pad, ASTM standard F3340听dictates a test in which听the pad is squeezed between a hot plate on the top听and a cold plate on the bottom鈥攔eplicating the location and weight of a sleeping human. Variables like ambient temperature and humidity levels are also controlled for, as is the inflation pressure of the pad, if it inflates. That cold plate is then held at 5 degrees Celsius (41 degrees Fahrenheit), while the hot plate is heated to 35 degrees Celsius. Over four hours, the energy required to maintain the hot plate鈥檚 temperature is measured. The less energy it takes, the better the pad is at insulating. F3340 dictates that three examples of a given pad should be tested, and they should be sampled across three test locations at different areas on the pad, to account for differences in construction and thickness. The average of those numbers is determined, and that in turn becomes a pad鈥檚 listed R-value. It鈥檚 this number that REI and MEC will begin displaying to consumers come听2020.听
That methodology is actually very similar to the way in which Therm-a-Rest currently tests its pads. In fact, of the three $50,000 standardized test machines currently in existence, one lives in Therm-a-Rest鈥檚 Seattle factory. The other two belong to REI and MEC. Bowers and Dean tell me that some small changes in methodology created by the new standard听will shift the brands鈥 advertised R-values up or down by a small amount, but overall they鈥檙e excited for the category鈥檚 newfound transparency.听
鈥淐urrently, you can report whatever you want,鈥 says Bowers. 鈥淲e believe our products perform at a high level, so we鈥檙e glad to have this more accurate comparison.鈥
Of course,听R-value is only one piece of the puzzle that is sleeping comfortably outside. Consumers will still need to account for varying approaches to providing support and stability, outright thickness of the pad, and its noise level. That鈥檚 in addition to weight and packed size, resistance to punctures, and of course price. There are听also practices users can employ to get the most of out of their pads, like inflating them with a pump in order to keep heat-sapping moisture from your breath out of them, and minimizing the portion of the pad exposed to cold air. But Bowers and Dean see the adoption of a unified R-value standard as an important first step in empowering campers to enjoy better sleep.听
鈥淲e need to educate people in a meaningful way what R-value means for them,鈥 Dean says. Starting in a little over a year, we鈥檙e at least going to have the data necessary to do that.听