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  1. #1
    Member tsshaw78's Avatar
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    Temperature vs Fill Power and Fill Weight

    I have been trying to get a sense of temperature rating based on fill power and fill weight. I'm sure somewhere there is an equation but in all my searching I couldn't find it. So I took the specifications from Hammock Gears quilts to derive one. I plotted the data and noticed linear trends based on fill power and on the fill weight. From that I derived the following parameters.

    mm = -0.005965761
    bm = 0.80763296
    mb = 0.012018967
    bb = 60.8219645

    T = temperature
    FP = fill power
    FW = fill weight

    T = (mm * FP + bm) * FW + (mb * FP + bb)

    Rechecking the formula, I get values close enough to the Hammock Gear specs to feel like I can use to get a ballpark idea of temperature rating for a down product.
    I'm curious if anyone has something better.
    A day camping in the rain is better than a good day at work,
    --Shaw.

    tsshaw78 is too hard to say on the trail - Just call me Shaw.

  2. #2
    cmoulder's Avatar
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    Ballpark

    Think inches of loft. And even then it's highly subjective with far too many variables to predict individual results.

    Any method you choose is merely a starting point for discovering what works for you.
    UL, because nobody ever asks "How can I make my pack heavier?"

  3. #3
    Senior Member
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    Temperature vs Fill Power and Fill Weight

    the biggest factor for warmth is the size of the baffles. you'll see that most manufacturers have nearly the same size baffles for the desired temp range. I think 2.5 inches of loft will be a 20 degree rated quilt from all the quilt makers.

  4. #4
    Senior Member BillyBob58's Avatar
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    Fill power should not matter for warmth as long as the thickness is equal. But at equal warmth and thickness the higher FP will way less in proportion FP difference. As others already said, with down, 2.5" single layer is usually rated at 20F, whether the FP is 700 or 900.

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