Sleeping Bag Testing
Over the past few years I have spent a lot of time in the cold-chamber testing sleeping bags with a heated manikin. The intent was to find new ways to design and construct sleeping bags. My hypothesis was that if we combined certain components, we could make a better, lighter, more versatile sleep system. I have tested sleeping bags together with quilts, blankets, and cots and discovered that an added layer of insulation does not add the same temperature increase at different temperatures. If you add a quilt to a 45F degrees sleeping bag you won’t get the same increase in temperature as if you added the same quilt to a 20F degrees sleeping bag. The increase provided by the same insulation at lower temperatures is less.
READING THE DATA
When I test sleeping bags this display reads the manikin’s average surface temperature, RCT Clo, and ambient temperature of the room. Clo stands for clothing. Clo is the thermal resistance of one business suit. So 1 Clo is one business suit, 8 Clo is the equivalent insulative value of eight business suits. RCT Clo is the thermal resistance; calculating the difference between the skin temperature of the manikin and the ambient temperature of the room, times the surface area of the zones, over the heat flux generated by the heaters. R-value is the imperial units which is the same scale as Clo which is metric. Clo is then converted to a temperature rating or a temperature range.
ISO 23537 AND ASTM F1720 STANDARD
ISO 23537 is a global sleeping bag standard enforced in Europe only. ASTM F 1720 is the US standard but does not convert to temperature ratings. Kansas State University (KSU) uses ASTM F1720 to get the data, then converts it to a temperature rating with their own conservative steady-state model and typical 8-hour sleep model.
In addition to temperature data, I use infrared photography to pinpoint key areas of heat loss. This combined data helped inform product development improvements.
In the ISO 23537 and ASTM F1720 sleeping bag standards the manikin is required to be dressed in a track suit.
When quilt testing, I put on a down hood to cover the head of the heated manikin. This insulates the head from heat loss where the traditional sleeping bag would have a hood. Quilts are not included in either ISO 23537 or ASTM F1720 because they do not have a back or hood, and cannot be rated according to those standards. I use the same testing standard as traditional sleeping bag, as I do with a quilt and a hood, but give a “recommended temperature rating” to the customer. I tell the customers that sleeping bags without hoods and quilts require additional clothing like hats or jackets with hoods to provide proper insulation during the night.
CAMPING MATTRESS TESTING
Normally camping mattresses are tested on a hot plate. In this picture a camping mattress is being tested using a heated manikin on a cot and a – 20F sleeping bag. This test was for a new ASTM standard for camping mattresses to determine R-Value of the camping mattress.