The European Sleeping Bag Temperature Rating Standard (EN13537) was supposed to be a great thing for outdoor manufacturers, retailers, and consumers. Finally, we’d be able to compare sleeping bag temperature ratings in a reliable and objective manner.
Ah, I have some bad news. I was browsing the Outdoor Industry Association’s web site last week and came across a June 2009 report that shows that the EN13537 standard is potentially misleading. I was shocked to come across this paper, so I contacted it’s author, Dr. Elizabeth McCullough, a noted textile scientist at the Kansas State University, and she explained the problems with the testing procedures to me in more detail.
Everyone’s Manikin is Different
But before I dive into those, it’s useful to understand how the temperature rating test is performed. REI has a good explanation of the EN 13537 standard in the experts tips section of their web site. Quoting them, “For EN 13537 temperature tests, a full-size mannequin with heaters and temperature sensors is dressed in one layer of long underwear and a hat. It is placed inside the sleeping bag being tested. The bag is laid atop an insulating sleeping pad inside a climate-controlled chamber. The mannequin is heated to simulate body warmth and measurements are taken of the air in the climate chamber and the “skin” surface of the mannequin. From these measurements, the insulation value of the sleeping bag is calculated.”
Currently, there are 5 different testing centers around the world that test sleeping bag temperature ratings using this setup, including Dr. McCullough’s labs at KSU. The problem, says Dr. McCullough is that every lab’s manikin is different and that there is no common definition of the thermal properties of the tracksuits, socks, hat (really a face mask), and sleeping pads, used in the test process.
Consequently, the results of the different centers may vary significantly, and while the test itself is scientifically sound, she’s been advocating for a consistent definition of these non-standard testing variables. As it stands, inter-lab variability is unknown, making it impossible to compare temperature ratings from the different centers.
Sadly, this has not happened. As it stands, the European standards group responsible for the temperature rating standard is not allowing the Outdoor Industry Association (OIG) to attend the group’s standards meetings. Dr. McCullough has advocated the creation of a consensus document from the OIG to the EN standards body protesting the current test definition, but progress along these lines has been slow. Dead slow.
Who Can You Trust?
Adoption of EN13537 is now widespread in Europe, and several American sleeping bag manufacturers including REI and Marmot have started labeling their retail sleeping bags with it.
Unfortunately, Dr. McCullough advised me that highly insulated sleeping bags could vary as much as 20 degrees (F) in their ratings and that there are no common test procedures defined for non-mummy bags. In addition, other researchers have documented additional problems with the test procedures (see papers linked below).
Where does that leave consumers and why haven’t sleeping bag manufacturers that have adopted EN 13537 been more forthcoming about these issues?