Loading... Please wait...

Subscribe to Wiggy's Newsletter » Receive updates about new products, specials, and learn about insulation technology

Having trouble receiving our newsletter? Resubscribe Here (Opens in a new window).

The Cold Truth

Posted by

This is the title of an article published in Outdoor Business magazine. The writer Lou Dzierzak decided to do some research into the temperature ratings applied to sleeping bags having noted a wide disparity at specialty outdoor stores. He further found there is no true formal standard for temperature ratings. He then heard of R.E.I.’s mandate concerning the EN standard (see my August 2008 newsletter).

The article is as I see it the best expose I have ever read about the subject of sleeping bags and temperature rating, as to how poor the information is that is published by those who market sleeping bags. Those who market sleeping bags have to some degree depended upon the Kansas State University Institute for Environmental Research (KSU) for their copper manikin tests. For the first time the co-director of KSU said about companies that pay for their service the following; “I have no control over whether or not the rating I put in my report is actually the one they will use in their labeling.” Imagine paying $1000.00 or so to have your bag tested and not using the information that is supplied to you. KSU has a chart that equates clo value to F. My suspicion is the marketers (s) of the bag (s) don’t like what they read in the report comparing clo to F so they do as they chose anyway. KSU is now testing sleeping bags from North American marketers (they say manufacturers, since they don’t actually produce the product I prefer to call them marketers) using the European standard. This I do not understand since in the article the same co-director at KSU states the following; “With the EN standard, there is variability {from lab to lab} in the insulation values that are measured for a particular bag or mannequin. They have taken steps to try to standardize that, but we know from feedback from manufacturers (must be European manufacturers at this time) that they get one insulation value from one lab and a different value from another lab”. Maybe I am wrong in my thinking; but why imitate a method that is flawed from the get go. The answer is simple; if you want to sell your sleeping bags in Europe through retail stores “you must test according to the EN standard.” This is according to spokesman from The North Face Company.

Others interviewed represented Sierra Designs (I actually though they terminated sleeping bag sales, guess I was wrong), Big Agnes, and GoLite. What they all did agree with is the simple fact that they do not have any clue as to how best to test a sleeping bag and that both existing techniques KSU and the EN methods are flawed. I was very surprised to read such blatant honesty. It is unfortunate that the companies who employ these people may have honest people but they are completely incompetent with respect to knowing their job.


There is no mystery as to how to properly test a sleeping bag. The first test is the insulation test. Many years ago a method was developed that works very well, the guarded hot plate. Make a box and insulate it on all sides. Place a flat plate preferably copper since copper disperses heat evenly (expensive copper cookware) on a heating surface such as a hot plate, heated serving tray that you can get in an appliance store. Place this in the box. Place the insulation on top of it as you would be using it in the construction of the sleeping bag. In my case it is of a uniform loft. Since other companies use some form of quilted product they should place a quilted form of their insulation on the plate. Heat the plate to a specific temperature; 100 degrees F. then place a temperature probe on the surface of the insulation and place a cover over the box. Time how long it takes for the heat to move from the bottom of the insulation till it reaches as an example 85 degrees F on top. The box should be in a room that has a consistent temperature from day to day. Perform this action each day at the same time for 10 or 15 days. Record the time that it takes each day to reach the 85 degree temperature. Discard the longest and shortest times. Add the rest and divide by the number of days of testing. Once complete get a second insulating medium and repeat the process. Once you have tested all of the different materials you will be able to say with complete clarity which is best.

I use different weights of Lamilite, the guarded hot plate only tells me my insulation is better than all the others, but it does not tell me what weight is good for what temperature in a finished sleeping bag. That must be discovered by trial and error. There is some help available that comes from Gerry Cunningham. Gerry for those of you who don’t know of him was the original owner of Gerry Outdoor Products. He in my opinion is the father of the outdoor industry. He wrote a booklet titled “how to keep warm” which I found invaluable in giving me an education in how to stay warm. I have applied this knowledge to my products. His guide to the thicknesses of insulation needed for various temperatures needed for clothing or sleeping bags is an excellent starter.

Based on his theories I made as an example my Ultra Light +20 degree F rated bag with two inches of thickness both top and bottom. Then I went into the field to actually use the bag. I was nude and in a tent on a ground pad. If you were to sleep under the stars you will not ever get an accurate read. It’s called convective air movement removing the heated air right off the surface of the sleeping bag. Light air movement is slower than when it is windy, but there is air movement to some degree. The better the ground pad the better. When you are nude the moisture your body generates does not stay on your skin surface; dry skin means warmth. If you sleep comfortably at +20 degrees the next time out go to 0 degrees. If you are marginally comfortable and ultimately do not sleep because you are cold (there is no such thing as a cold sleeper; when you are cold you do not sleep) then you know you have a +20 degree rated bag. Now that you know the temperature rating, weight the bag and note the size. The Wiggy’s Ultra Light in a regular length; 80 inches long and regular width 31 inches wide and has a weight of 3.25 pounds on average. This bag will fit a person who is 5’8” and weight about 150 pounds. Taller and heavier people must have a larger bag so naturally they weigh more.

This is initially the method I employed. Yes I have reports done at KSU on my bags paid for by the Celanese Company. These reports contradict the historical performance of my bags. If one were to read their assessment of my Antarctic bag which is rated for -60 F use, I would not sell a one. They had it clo rated for 4.9 clo which is about 10 degrees F. Imagine purchasing a 7 pound bag for 10 degree F use, I can’t. Another method I have been able to employ happens to include the military. This is a situation that can not be minimized. I have supplied 200 bags in one instance to the Marine Corps; the Desert Bag. They were issued to 200 men all about the same age, all wearing the same clothing, all eating the same food, all involved in the same activity at the same time for 30 days. The desert bag is a down sized Nautilus which is rated for +40 degrees and higher. These Marines as was reported to me experienced temperatures as low as +29 degrees F and 95 percent were comfortable; i.e. they slept. It is impossible to argue with a test done as this was.

Over the years 22 now I have had a customer question the temperature rating, when you consider the number of bags produced, several hundred thousand not all will be satisfied. However, it is less than one percent of all sales.

Is the copper man testing regardless if it is done in the USA or Europe capable of giving the same results absolutely no? Imagine a hang tag with a clo rating or an EN rating on it. People in the USA understand F and the rest of the world understands C.

Therefore, there is an accurate test method. As for the differences in people, women, children and older people all of whom have less muscle mass than young men will need as an example a 0 degree rated bag when the young man uses a +20 degree bag. Some will not necessarily need to wear clothing but will regardless. In this situation the Lamilite excels at driving the moisture from the clothing and out of the bag. No other sleeping bag has ever demonstrated this action. There are other variables such as food intake to consider but if you don’t have much of either the deficiency is minimized by the Lamilite insulation.

Maybe one day those in the employ of the companies who claim to make sleeping bags will actually field test their bags rather than to rely on a method that has never worked does not work now or will ever work in the future. I am confident in saying machines will never be able to replace humans when it comes to testing sleeping bags.

Wiggy's Signature

Our Locations  +  Contact

Corporate Office & Factory

To place an order, please contact our corporate office & factory at:

Wiggy’s Inc.
PO Box 2124
Grand Junction, CO 81502

Store Location

2482 Industrial Blvd  •  Grand Junction, CO
(970) 241-6465

+1 (866) 411-6465 f:  (970) 241•5921 e:  

When it comes to extreme cold weather gear, Wiggy's has you covered.

Check out all our products from sleeping bags & shelters to footwear & clothing. Our uniquely developed continuous filament fiber called Lamilite insulation is what sets Wiggy brand insulated products apart. What is Lamilite and why does it perform better than all other forms of insulation? Click here to keep reading & find out more »

© Wiggy’s Inc. All Rights Reserved.