-7º Pads vs Underquilt on MN Winter Night

[BillyBob58]

Much as I would love to buy an underquilt, having just splurged on a Blackbird and Superfly, my funds are pretty depleted. I tried a combination of blue CC foam pad, truck window sunshade with a half z-rest lying crossways under my shoulders for -1° to -3° night last night. I was in a -15° sleeping bag and was fine until about 6 a.m, when mild CBS started. While I'm sure that the UQ option is significantly more comfortable, I'm just curious if anyone knows the R-value comparison of a Winter UQ and how many blue CC sleeping pads it would take to have the same effect. Again, this is not so much about cushy comfort as it is about functional comfort. Thanks.

I don't know exactly, but no doubt you can exceed any single commercially available UQ( well, I guess, are there any rated much more than about zero? Probably there are if custom) with enough pads. Some here have done at least minus 22F with pads only, but I can't recall how thick their pads were. As for R values, it runs more or less like this: every 1/4" of CCF = ~ R1.1,
so 1" = ~ R4.4, 2" = 8.8 more or less, probably a tad less as you get thicker so maybe only 8.6 for 2". But that is a lot of R, and of course it is wind and water proof can even be laid directly on the ground. R value Probably varies some with who is making the CCF. Then maybe about 13(12-14) degrees F per R. So 2" CCF with an R8.6X13F= 111.8*F protection. 75(or 70 if you prefer) - 111.8= minus 36.8F(or minus 41.8 starting from 70F if needing nothing at 70).
For 1", R ~ 4.3 = 55.9. 70F - 55.9= 14.8F(add 5 if starting from 75, or about 20F)
1/2"=R2.2X13= 28.6 70F-28.6= 41.4F

So that takes care of pads, what about UQs R value? Well, that is a bit tougher. But, looking at Climashield quilts which are rated in CLO, 1 R = approximately 1 CLO. (Actually, it's more like 1.14 CLO per R, or .88R per CLO). But for quick in your head calculations, just use 1 to 1 and you should be in the ballpark.

So, CS weighing 5 oz per sq, yd. has a CLO of ~ .82 per oz X 5 oz = 4.1 CLO. That would be ~ 3.6R. X 13= 45.76. 70F-46.8= 23.2 warmth rating for a CS 5 oz/sq.yd quilt, compared to about 41F for a 1/2" pad or 15 for a 1" CCF pad. To be closer to that that quilts rating, you need the same R value of 3.6, or 3.6/4.3(R value of 1"pad)= .84" pad to = the warmth rating of a 5 oz/sq.yd CS UQ. Remember, all warmth ratings for the CS are based on perfection of fit, IOW probably a zipped up draft free sleeping bag. Quilts might not be quite as warm, even a small draft and all bets are off. And for pads, CS and R values, all is based on some mythological average sleeper, but who ever really knows if that's what they are?

And for down? Well you have all those different fill values, but some say that it matters not as for warmth per inch, but only for warmth per weight. So supposedly 1" of 550 is approximately as warm as 1" of 850, more or less. So I have seen a table that says 1.1" of 550 down has a CLO/R of 4.8 ( they seem to be considering CLO and R the same). http://www.tadvgear.com/page4.htm
But this table can not be right if the above calculations are correct. If this is right then 2.5" single layer of down, normally rated at ~ 20F, would have a CLO of 10.9. Reducing it to an R value as we did above that would be an R value of 10.9X.88= 9.6!
Or 9.6X13F= 124.8! 70F-124.8= minus 54.8F warmth rating for 2.5" of loft! Even the 1.1" they have as a CLO 4.8 would be a 15F rating for 1.1" loft, no way!

I find this much more reasonable:
http://en.wikipedia.org/wiki/Clothing_insulation

Some basic insulation values can be considered as examples of typical conditions^[5]

• naked body: 0 ;
• summer clothing: 0.6 clo ;
• ski outfit: 2 clo ;
• light polar equipment: 3 clo ;
• heavy polar equipment: 4 clo ;
• polar down duvet: 8 clo.

Sorry if I have grossly miscalculated in the above, it's quite possible I did.

[Shug]

I'd try two real pads. Skip the window shade. I always used an SPE. Or check out the ENO HotSpot.
Carry forth.
Shug

[PappyAmos]

Originally posted by BillyBob58
I don't know exactly, but no doubt you can exceed any single commercially available UQ( well, I guess, are there any rated much more than about zero?

Commercially available - well the guy up in Thunder Bay had UGQ make him one with, was it 7" of loft last year? Any way they can be had if you are willing to pay for them.

[SirMarkos]

Sorry if I have grossly miscalculated in the above, it's quite possible I did.

Holy crap! You are a wealth of insulation information but I've gotta grab an aspirin and a nap now

[allhansondeck]

Ditto, on curious what Shug has changed.

[Shug]

Ditto, on curious what Shug has changed.

Well....I don't use pads anymore. Underquilts all the way)))))
Shug

[mixter]

Numbers are great but the best thing is to try both. Temperature was 35f. Tried 0 degree under quilt for couple of hours and pad that's rated R 5.7 and pad rated R 3.2 and gave the under quilt my rating of about 4.5
Also I have a 4 inch self inflatable pad and its warmest thing ever I think like R value 8 but it's bulky too

[Rollintent]

I started reading this thinking it was a new post at first and was wondering what kind of parallel universe I had entered. Then I saw the dates of the OP. I'm pretty sure I have exhausted the entire library of Shug's videos on Youtube and have never seen a pad in use in any of them. How was the thru hike by the way?

[obxh2o]

I started reading this thinking it was a new post at first and was wondering what kind of parallel universe I had entered.

Ha! I read the first post without looking at the date and started wondering if I had missed and eclipse.

[Hickery]

Ha! I read the first post without looking at the date and started wondering if I had missed and eclipse.

Me too !! I had thought my old buddy Sean (Shug) had gone nuts (again) .Da Ha !!!