I realised the other day while trying to compare down jackets that while PHD don't list fill weights for their jackets they do list the total weights with either (European rating) 800 or 900 fill-power down for medium-size jackets on their "design your own down jacket" mini-site. Using the relationship between fill-power values it is theoretically possible to calculate the fill weights of those jackets:
PHD Ladakh (-5C TOT, similar to Minimus): 108g of 800FP or 96g of 900FP
PHD Toubkal (-15C TOT, most similar to Yukon): 162g of 800FP or 144g of 900FP
PHD Svalbard (-25C, similar to Hispar): 207g of 800FP or 184g of 900FP
PHD Denali (-35C): 306g of 800FP or 272g of 900FP
Even keeping in mind that PHD use the European fillpower ratings, which means about 8% loftier than the equivalent US rating, these seem very low for the temperatures quoted.
The Toubkal/Yukon only gets around 162g of US850/860 down, whereas the comparable Rab Infinity (size L) gets 210g of US850. And the Svalbard/Hispar only has around 207g EU800 down for a -25C rating, which is very low compared to the 310g of EU800 in the Crux Lava (size M), and 271g (size M) of EU800 in the Valadre Immelman, both rated to -20C.
If you assume size M is roughly standard across these manufacturers (I believe it is), then I figure there are three ways to account for these discrepancies. 1) my maths is wrong, 2) PHD's site is not very precise, or 3) there is a vast difference between PHD's temp ratings and those of other manufacturers. I don't think my math is wrong since they make sense given the finished weight of the products given the weights of the materials and the construction methods they use. Since PHD's site lists very specific weights I can only assume that they are confident in their numbers, so I'm not sure what to make of their temperature claims.
I know PHD gear is used by athletes and professionals all over world, but I can't believe that PHD gear is somehow so well designed that they can use 50% less down than other manufacturers to achieve the same insulation levels. Therefore, I think PHD's "typical operating temperatures" shouldn't be used to directly compare with other brands like Crux and Valandre, it seems to be very much a "limit" rating rather than a "comfort" rating.
