Is Enlightened Equipment temperature rating accurate?
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Found this sign at my local REI – the same REI that soon will require R-values for sleeping mats, and quotes EN values for sleeping bags based on R 5 mats:
Other pad vendors have similarly misleading and potentially dangerous guidance.
Until manufacturers and sellers start posting notes alongside sleeping bags like “rated temps require an R5 or higher sleeping mat,” and next to wimpy mats like “this mat isn’t warm enough to support sleeping bag temp ratings”, consumers will be mislead.
Not holding my breath.
— Rex
PS: Zenbivy is the only one doing something like that AFAIK:
Can someone point me to online documentation that states EN ratings are with an R5 pad?
Probably not.
You see, the subject is very complex, with ‘warm’ sleepers, ‘cool’ sleepers, males, females, different metabolisms, different test conditions, different (brand) enthusiasms for the EN Standard, national differences, and so on. In addition, since it is complex, testing to the EN Standard tends to be expensive, which accounts for some commercial reluctance.You will hear comments like ‘Our bags are 5 degrees warmer than brand X, so we label them accordingly’. In addition, it is a well-known FACT that American manufacturers usually claim their bags to be around 16 C better than they measure under the EN Standard. This is a sad reflection on many USA mfrs.
Mammut (Europe) include this pic in one of their tech papers on ratings, using data from their own testing (I think):
So it is not just the American brands which wander.Unfortunately, while the EN Standard is fairly solid in its own way, it does have some ‘less clear’ sections. One of these is the rating or R-value for the mat to be used. They get as far as saying that the mat must be warm enough that further increases will not change the results. I can understand their thinking, and that will be OK for testing, but the spec does not help us (the users) much.
If you read our SoTM on air mats at
https://backpackinglight.com/airmat_sotmr_part1_2011/
https://backpackinglight.com/airmat_sotmr_part2_2011/
you will see that available mats cover a huge range of R-values. But what is missed in the EN Standard and in almost EVERY vendors specs is a mention of how ‘blown up’ the mats is when tested. Quoting from our article about one mat:
When the mat is fully inflated (44 mm thick) the R-value can be as high as 4.5, but when the mat is squashed down to between 14 and 18 mm thick (as it might be under your hips) the R-value is only about 2.0.The problem with a mat which is blown up hard (to get maximum insulation) is that it becomes rather uncomfortable. Much greater comfort is to be had when the mat is deflated a bit, so it conforms more to your body – but then the thickness and the R-value go down.
I measured R-values from 1.0 (empty pool-toy style) to over 15 (down air mat). Note that the R-value of 1.0 is cold under most conditions.
A value of 5, if maintained while you are sleeping on it, should be fine under most conditions not on snow.
HTH
CheersMike Glavin from Zenbivy here. Two thoughts to share:
- The source for the “R5” number is included below for your reference.
- The number does not matter, only the mattress used in the test fixture (and its pressure) really matters. So measuring the fixture mattress is really the only way. Funny, after getting some anomalous results on a test recently, one thing I noticed is that the mattress had changed, and wondered if that could be a factor. Check out the variation in mattress in the enclosed photos (some are Kansas State “stock” images where you can see the logo on the mattress).
Testing Sleeping Bags According to EN 13537:2002: Details That Make the Difference
Kalev Kuklanea & Valter Dejkeb
a Division of Ergonomics and Aerosol Technology, Lund University, Lund, Swedenb Department of Textiles and Plastics, Swerea IVF AB, Mölndal, Sweden Published online: 08 Jan 2015.
The mattresses used were a 10-mm thick foam-rubber mattress with a thermal resistance of 0.230 m2K/W, a 38-mm thick Therm-a- Rest® (Cascade Designs, USA) ProLite 4 with a thermal resistance of 0.516 m2K/W (labelled with R 3.2 = 0.496 m2K/W) and a 40-mm thick older model of Therm-a-Rest® with a thermal resistance of 0.868 m2K/W. The standard requires the thermal resistance of the mattress to be within the interval 0.79–0.91 m2K/W for calibration and “mat representative of the habits of sleeping bag users” for testing.
From the final sentence above, you can convert the required thermal resistance for the mat from 0.79-0.91 m2K/W to R (multiply by 5.678.), which is R 4.49-5.17.
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