CLO vs Thickness
OK. I'm trying really hard to decide on what to use for my underquilt. It will either by Climashield XP or HL.
Can somebody help me understand the relationship of CLO and thickness?
The 5oz HL has a reported CLO of .68 according to a recent post. Loft is around two inches.
The 5oz XP has a reported CLO of .82 according to the same post. Loft is 1.2inches.
Given the loft, would the thicker HL be warmer or is the CLO value more important. Or am I "straining at gnats"?
Loft and CLO are two different things... for instance, 2 inches of loft for a particular insulation will always be warmer than 1.5 inches of the SAME insulation.
You can't compare 1.5 inches of one insulation type with 2 of a totally different type unless you have a reference number (such as R-value or CLO).
In the case you've outlined, the HL would have a total CLO of 3.4 The XP has a total CLO of 4.1.
SO.... the XP is about 20% better insulation, if the numbers you give are correct, even though the HL is thicker!
One of the nice things about CLO is that it relates insulation value to WEIGHT. There are more efficient PER THICKNESS insulations out there, but they might not be as efficient PER OUNCE, and when backpacking the weight makes all the difference.
Hope this makes it clear, and that I've done my math correctly. :P
Happy New Year!!!
my limited understanding...use loft when comparing like items of different thickness (xp vs xp)
Originally Posted by jbo_c
Use clo when comparing different materials...(your question of xp vs hl)
I use xp and it is VERY warm for minimal thickness.
Thanks, Ted. I understand what your saying, but based on the info you gave, your formula would be for total insulation per ounce, not per inch(or whatever thickness measurement).
Is the CLO measurement independent of thickness? - or is it based on the stated thickness of the material?
Now that I think about it, that would make sense. Product X is designed with a loft of 1". At that loft, the CLO value of X is .60. Product Y is designed with a loft of 3". At that loft, the CLO value of Y is .90.
In that example, the CLO is dependent on the designed loft of the material. That makes sense to me, since, for instance, the Climashield XP if compressed from 1.2" to 0.3" surely would not have the same insulation value.
Am I thinking right?
CLO is a measure of insulation per OUNCE of material. So, if your weight per square yard increases, it's the same thing as saying your loft increases! (twice the weight per square yard = about twice the thickness, or "loft". :)
You're quite right, the CLO values are for the material in its "lofted" state. Any compression will reduce insulation values. That's why lying on a down quilt inside a hammock doesn't keep you warm. The down is compressed to a small fraction of its "fully lofted" state!
Some synthetic insulations don't compress very much... for instance Thinsulate. Thinsulate isn't the material of choice for quilts because it tends to be a bit heavy and doesn't compress very well... this actually makes it GREAT for sleeping on TOP of, precisely BECAUSE it doesn't compress much! Unfortunately, it'll take up a lot of room in your pack. So what's the cure? a highly compressible insulation that you hang OUTSIDE your hammock, where it can't compress due to your body weight!
I never would have thought of hanging a quilt outside of my hammock if I hadn't read it here at the Hammock Forums.
Note that CLO is PER OUNCE. So if "X" has a CLO of .6, its total CLO is just the weight of the insulation fabric (per yard) times the CLO value.
i.e. (CLO .6) x (5 oz/yard) = 3
Next, take your result (3) and stick it into this formula.
Your result (if you sleep "warm", like the Captn does) will be a quilt good down to around 35 degrees.
The fabric you face your quilt with can make a difference, too. I've read that a vapor barrier fabric (like silnylon) can add another 10 degrees, which would bring you down to about 25F!
Here's another good POST which should help you in your planning.
Good luck, and happy new year!
The subject of CLO has been talked about A LOT over at thru-hiker.com. If this subject is still clear as mud, you may want to try that recourse.