Eric,
You said in part, “Here’s a question that always bugs me. How much of an effect does the shape of down baffles have on the EN-rating?”
Odds are the baffle design is not what accounts for the majority of the 5F difference in the EN 13537 ratings given the bags have the same dimensions and same amount of down but, 50FP lower on the new. Only the tailoring changes to better seal the hood and eliminate foot compression for the test dummy fit would account for this much difference.
I take a thermal image of every garment that I test the iClo of. The most recent garment I tested was the LUL HyperDry Vest on 5/9/16. It is shown below just to illustrate how the seams show up in a thermal image. Temperatures in a thermal image are not linearly related to the insulation values. They are sewn through seams with seam heat leakage about in the middle range of all garments that I have tested (includes sewn-through, box-baffled, and complex box-baffled). The seams make up a very small percentage of the total surface and negatively impact the insulation value accordingly.
- LUL HyperDry Vest in Environment Chamber Photo
2. LUL HyperDry Vest in Environment Chamber Thermal Image
3.Thermal Values
4. Baffle Designs
The following table lists a few of the best and the worst seams designs I have tested. As you can see, seam heat leakage, is negligible in both box baffle designs and even sewn-through designs, if you use a windshirt or hard shell over the jacket. The same concept would apply to using a sleeping bag or a quilt in combination with a light bivy.
Note that standard environmental test condition is a 95F guarded hot plate (max skin temp) and 68F ambient environment. The closer a seam value is to 95F, the worse the heat leakage (Max F in table below).
The MB Permafrost baffle is welded, not sewn, to the Gore-Tex Windstopper outer layer. It is hard for me to I envision a much more reduced heat loss than that construction.
The MEC Reflex (14 oz 800 fill) was construction with a proprietary offset box baffle and leaked more heat than the MB Permafrost seams.
Company’s attempt to differentiate their products based on their unique baffle designs. I haven’t seen a benefit in my testing nor have I seen any neutral research to support the marketing claims. Ask a vendor you are interested in to send you a thermal image of their bag and a equivalent WM bag to prove it to yourself.
Typical EN 13537 Test Result Report
Sleeping bag seams heat leakage is such an insignificant component of an EN 13537 rating, that it not even normally tested for. The following is an example of the laboratory report that the manufacturer receives after a complete EN 13537 test battery. See EN 13537 Report
3.Thermal Values
4. Baffle Designs
