Eddie Bauer First Ascent Downlight Sweater Review
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Steven,
For the average person doing camp chores sheltered from the wind, the MH Nitrous thermal tests 43F – 27F. For the same test environment, the EB First Ascent 800 thermal tests 40F – 22F. Although the EB First Ascent is actually warmer than the MH Nitrous, they will appear to be equivalent warmth jackets since the average person can only judge the feel of insulation granularity in increments of .5 clo. The EB is .3 clo warmer. These measurements ignore down loft as the theoretical determinant of insulation value.
Loft as the primary determinant of a garment's insulation value has been a consistent BPL editorial position as far back as 12/16/2001. See http://www.backpackinglight.com/cgi-bin/backpackinglight/00094.html . This article states in part,”… Measuring the loft of a down garment is a difficult thing. Each of the many chambers has a slightly different loft. Measure a jacket once, pick it up and shake it, put it down and measure it again, and you won’t get the same number. Measure it a day later and you’ll get yet another number. All of the jackets increased 10% to 20% in loft over the week of observation. As such, my loft figures are probably as good as you can expect. Under trail conditions where it has been stuffed in your pack all day, you’ll likely have less loft. I measured each jacket four times over the course of the week. Each time I made ten measurements on a jacket, four on the torso and six on the arms. A level was used to make loft measurement more accurate. I took the best two (namely, loftiest) of the measurement sessions for each jacket and averaged them for the loft measurements reported in the comparison table. The weighted loft figure I report in the comparison table takes into account that torso loft covers more of your body and is more important to overall warmth than sleeve loft. Weighted loft is calculated as follows: Weighted Loft = [(2 x Torso Loft) + Sleeve Loft] / 3 Thus torso loft gets twice the weight of arm loft in the final loft figure.
Skipping forward about 8 years, “loft determines insulation value” is still the standard BPL editorial position and loft measurement inconsistencies still exist. As a recent example, look at BPL’s reported down loft of the Montbell Ex Light Down Jacket. Mark Leaman posted to the forums on 01/13/2010 07:28:41 that Will measured the loft of the EX jacket as .75” in his backpackgeartest review. In Will’s BPL Mountain Hardwear Nitrous Jacket Review table he measured the loft of the EX as .5”. In Will’s BPL PHD Mountain Software Ultra Down Pullover Review table he measured the loft of the EX as 1”.
Similar inconsistencies exist in the BPL measurement of sleeping bags that are very easy to see by comparing the BPL measured loft values with the EN 13537 test results. Reference http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/mb_post_form.html?po=edit¬e_ id=219939
&forum_thread_id=26645 . Subsequent to my post, the BPL measured 2.5” loft for the Marmot Hydrogen was changed to a 2” measured loft. This was the original table in the article.
Even if you specified a common method to get a loft reading, there is no Domestic or International standard that recognizes loft as a determinant of thermal resistance (insulation value). Only a traceable national lab calibration, in combination with a guarded hot plate, a thermal flow meter, or a calibrated manikin is recognized. If you have nothing else to go by, then a ruler will give you a gross approximation but to expect accurate thermal insulation resolution is a mistake.
Down loft measurements are not a reliable method to measure the insulation value. The table, in the article, lists the loft of the MB Light Down Jacket as 1.1".
Another BPL staff member reported the loft as 1.25" in his forum post http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/10136/index.html?skip_to_post=73469#73469
I just took 2 pictures of a MB Light Down Jacket's loft:
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