I'm doing a new Top Quilt and wanted to get idea what temperature it should be good to. I started filling the baffles and the loft is 2 3/4 inches. Before I fill all of them I would like to be sure I'll get the temp. rating I want. I'm hoping for 10*. Any help would be great.
It sounds like you are ok. Here is one set of recommendations.
Usually I see:
2 inches = 30 degrees
3inches = 0 degrees
I'm more accustomed to 20 degrees F per inch until you hit 20 F. The insulating value is not really linear, so you will begin to see a law of diminishing returns apply around 20.
HG has 4" of down for a 0 rating, and JRB has 3.5" for "single digits".
The "20 degree per inch method" begins at 70 F (as no insulation is needed above 70). So 1" equals 20 degrees of insulation below 70 to yield a 50 degree TQ (70-20=50). A 2" would then be 70-(20X2)=30. So your 2.75" would be 70-(20*2.75)= 15. That is really pushing it since down loses efficiency beyond that. The next inch will probably only give you 10 degrees more warmth rather than 20, so a 3.75" TQ would be good somewhere around the 5 degree range.
and just to throw another wrench in... your rating will also be determined by if you sleep cold or hot, if you've had enough to eat, what you wear to sleep in & weather conditions.
I've found myself in warmer temps, freezing with a quilt that kept me roasting before. I now like to have, especially my under quilt, rated well below the actual temps that I'll be in. My upper top quilt is also rated lower, just not as low as the bottom quilt.
Do you already know if you're a cold or warm sleeper? That would help determine what temp your quilt should be rated at.
I use Western Mountaineering's formula for loft/temperature ratios which closely follows Wisenber's post above. WM is a sleeping bag manufacturer that many consider one of the finest sleeping bags and they have a reputation for being conservative ( read honest) in their claims.
Temperature = 67 - 18*Loft
Mike
"Life is a Project!"
This all sounds good to me. My under quilt is a solid 3 in. and has been to 20* and I didn't even feel cold underneath. The top quilt I had was just to small at 44in x 74in. and although not cold at 20* I could tell it was at its limit at 20*, it has 2.5 in of loft. I'm making this on 52 inx 81 in, tapered to 42in at the foot, and want the loft at 2.75 in to 3 in. I'll post pictures after the downs arrives and the quilt is finished.
I do not expect to be under 10* but I don't want to be cold if it does get in to the teens. Nor do I want to be cold if im tired, under feed and it gets to 20*. I planing to use the first quilt during the summer and this one March, April and May of my hike.
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