View Full Version : additive sleep system ratings?
what do I get if I add, for example, a 40° quilt or bag on top of 20° quilt or bag?
or a 40° on a 40°
etc...
I know, I know....tons of variables, very personal experience kind of things, which sleep pad, is it wet, etc....
Lets say we are limiting the discussion to non arctic and non alpine conditions, sleep pad that would be ok for the ultimate temps, etc...
but generally speaking
is there any sort of widely accepted rule of thumb equation to loosely predict what I might expect?
as in like maybe take half of the second quilts rating off the base layer's rating, just as an example....
Do you think I might expect comfort down to a ballpark of 20° with two 40° quilts?
futureatwalker
12-14-2017, 17:34
Do you think I might expect comfort down to a ballpark of 20° with two 40° quilts?
No.
But I think you would be o.k. with a 40 degree bag inside a 20 degree bag, in actual 20 degree overnight temperatures.
I did exactly this last weekend. I had a 40 degree Kelty down bag inside an (older) 20 degree North Face down bag. I was warm enough - just. In the morning my water bottle was frozen inside my tent, and it was 17 degrees outside. I tend to sleep cold.
So, in my experience (above, and elsewhere), adding bags together does give you more warmth. It's not arithmetic though. The key is to increase loft. The more loft you have the better, and two bags is a good way to do this.
You
No.
But I think you would be o.k. with a 40 degree bag inside a 20 degree bag, in actual 20 degree overnight temperatures.
I did exactly this last weekend. I had a 40 degree Kelty down bag inside an (older) 20 degree North Face down bag. I was warm enough - just. In the morning my water bottle was frozen inside my tent, and it was 17 degrees outside. I tend to sleep cold.
So, in my experience (above, and elsewhere), adding bags together does give you more warmth. It's not arithmetic though. The key is to increase loft. The more loft you have the better, and two bags is a good way to do this.
Next time layer the 40 bag over the 20 bag. Squashing the 40 inside the 20 doesn’t give the 40 a chance to loft.
Long underwear, wool socks, hat and gloves help too. If the 20 bag has a hood draw it up around your head and face. Every little bit helps.
I’ll be doing all of that with a single bag tonight in my backyard. We’re having a string of nights in the 20s-30s and I’m testing my gear.
Good luck!
Wayne
Sarcasm the elf
12-14-2017, 17:57
Enlightened Equipment has an article that discusses layering their quilts specifically, which is complete with an approximate layering equivalency chart. It's not exactly the same as sleeping bags but is a good starting point.
https://support.enlightenedequipment.com/hc/en-us/articles/115002770588-Layering-Sleep-Systems?mobile_site=true
wordstew
12-14-2017, 19:36
It's coincidental timing that you post a link to the EE article about stacking quilts. I just got myself a thermarest proton blanket and plan to stack it with a UGQ 20 degree top quilt just as the EE article suggests...light synthetic quilt over your down quilt. I believe 60 bucks for the greatest blanket a pretty good deal and extends the lower limits of my sleep system
In EE's "accessories" section, you can find some elastic straps designed to keep 2 quilts attached to one another. You can also find female and male individual snap clips that could be sewn on the TR blanket
very interesting.... and thanks for that link to the article, Sarcasm. And I think very helpful to me in understanding the big picture of bag ratings
I didn't wade into it too deep tonight to check all the numbers, getting too tired..... but at first glance it looks like the math is based on a 70 degree datum
so a 40 degree quilt gives 30 degree benefit from the datum
a 20 degree bag gives a 50 degree benefit from the datum
50+30=80 degree benefit
70-80=-10 degree rating
seems like plausible logic to me.....
except, I'd question the use of 70 degrees as the datum
in a 70 degree room I still want a blanket
I'd say it's more like around 80 before i shed everything...depending on humidity and air movement of course....
but that 10 degree datum in MY comfort level explains the fact that a 40 degree system only feels good down to maybe 50.....
For easier calculation, industry introduced the R-value. When stacking insulation you just need to add the respective R-values.
Unfortunately the R-value of sleeping bags is usually not exposed to the user.
The temperature range the bag manufacturers give is just a Mickey Mouse number and can be taken as a rough approximation only.
When using double sleeping bags, I agree with Venchka that the more wide-cut bag has to be outside, and the more slim cut inside.
If using a synthetic and a down bag simultanously, usually the synthetic should be inside, and the down outside.
But then, ist all up to personal preferences, and the very specific setup you are using.
I used to spend a lot of nights in the backyard or on the terrace, and when I woke up in the middle of the night being cold in my light down bag, I just draw a heavy wool blanket over me. A big "theoretical" no-no as the heavy blanket will compress the lofty down, but still - it was a perfect help for me.
When using a combination of down and synthetic, there are two significant factors to be aware of. First is typically synthetuc is heavier, so layering down on top will maximize loft. Second, is the dew point will most likely occur within the top layer, so it would be better to put synthtic on top. These two factors must be balanced by the user depending on the trip requirements. On weeklong+ winter trips vs a supercold overnight for example.
According to Monty Python the answer is 11 meters per secondIn the end, it's concluded that the airspeed velocity of a (European) unladen swallow is about 24 miles per hour or 11 meters per second. But, the real question is not about swallows at all. King Arthur in the movie had two coconut shells that he banged together to simulate the sound of a horse galloping.
.... On weeklong+ winter trips ...
I have not yet done more than two-three consecutive nights in very cold conditions, and I've managed with a single superwarm down bag.
But up to my understanding it would be very helpful to use a vapor barrier (bivvy bag) inside the bag to not let escape much moisture out into the insulation in the first hand.
Just Bill
12-15-2017, 11:46
I'll neatly sidestep the misinformation shared thus far....
Blw2... you were on the right track. The formula behind the EE chart is:
70*- (rating of outer bag/quilt)= how many degrees it will lower the inner bag/quilt's rating.
So in your original question... 40*+40*....
70*-40*=30* added. So stacking your 40* on your 40* results in 10* combined rating. (40*- (70-40))=10*
In real life this works fairly well. The ideal combo seems to be a 45-50* summer quilt over a 20* or so winter quilt.
I tested my 45/25 Primaloft Gold quilts quite a bit. Though 45* synthetic plus 20* down is better overall.
As you approach zero... all insulation formulas break down. So a minor modification I suggest.
Below 20*... add back 10*
Below zero... add back 20*
Test your combo in safe conditions.
My 45*+ 25* should equal zero. (25*-(70-45))
In real life though that worked out closer to 10* in testing... and that matches the calculations I would do if I were to build that bag from scratch.
Same goes for a 25* synthetic over a 20* down. (20*-(70-25)= -25*
In real life that got me to -10 or so... though I haven't had the kind of prolonged deep winters that allowed much testing beyond that in Chicago.
So again... EE's math works well, with the adjustment I suggest for deeper cold.
Quilt stacking is an ideal solution for the camper with a summer TQ and three season bag looking to get in that winter weekend or overnight without breaking the bank.
Realistically... this is 99% of those looking for a winter insulation solution. And your 'big money' is better spent on a good summer and three season combo as that's most of the season for you.
When I was selling these I used to offer the 'buy two get one free' sale. 45* and 25*... with a free 10* bag when combined.
That gives you reliable 50*, 30* and 10* options for often the same cost as a single quality winter mummy bag. Perfect for most of us.
Stacking quilts is a nice option, but things can go wrong. Fit can be bad... user error can go up (top quilt slides off inner quilt).
It's a nice tool in the toolbox to push your gear's versatility here and there. You need to play with it and educate yourself before you push it though.
My quilts were cut to stack and designed to work in this manner....so ideal conditions so to speak. Not as critical with down as some might have you believe, but very critical with synthetics. Peter at EE confirmed with his testing that same size down quilts worked the same as two different sizes. Some discussions at BPL backed up this with some lab data regarding density of fill and thermal performance of down.
As you more frequently winter camp or plan to do so in challenging conditions... it's time to bite the bullet and buy a real bag rated appropriately.
The entire rating system is a bunch of made up BS. The sleeping bag rating was based on what temp it was when your companions found your frozen dead body in the morning. Nobody can tell you what a bags rating is...you tell them. To me 20 degrees is pretty cold and I will be hating life in a 20 degree bag unless I am wearing every bit of clothing I have. If all I have is 40 degree quilts or bags I want about 6 of them if it's going to 20 that night. My answer is that you can't look this up in a book. You can't base it on what some bag maker puts on a marketing label. You are going to be figuring this out the hard way.
wordstew
12-15-2017, 18:17
The entire rating system is a bunch of made up BS. The sleeping bag rating was based on what temp it was when your companions found your frozen dead body in the morning. Nobody can tell you what a bags rating is...you tell them. To me 20 degrees is pretty cold and I will be hating life in a 20 degree bag unless I am wearing every bit of clothing I have. If all I have is 40 degree quilts or bags I want about 6 of them if it's going to 20 that night. My answer is that you can't look this up in a book. You can't base it on what some bag maker puts on a marketing label. You are going to be figuring this out the hard way.
Can't agree with you more. My young buck days in the military I would leave my sleeping bag in my locker just sleep on the foamy OD green bed roll, use the field jacket as a blanket add poncho/liner if I felt a chill. Wake up from a great night sleep and brush the snow off me ready for another hard charging day.
Now into my semi golden years if the thermostat goes below 70 degrees in the house I think I'm ruffing it when using just one lofty down comforter.
Moral of the story is everyone is different, test your gear in a reasonably safe environment see what works for you.
ggreaves
12-15-2017, 18:25
You are going to be figuring this out the hard way.
Or, buy a Wiggy's bag.
wordstew
12-15-2017, 19:01
In EE's "accessories" section, you can find some elastic straps designed to keep 2 quilts attached to one another. You can also find female and male individual snap clips that could be sewn on the TR blanket
If you want an item that can be duel purpose and attach multiple quilts check out "lock laces"
https://www.amazon.com/LACES-Elastic-Shoelace-Fastening-System/dp/B007DLVLBQ/ref=sr_1_4?ie=UTF8&qid=1513378748&sr=8-4&keywords=lock+laces
wordstew
12-15-2017, 19:02
In EE's "accessories" section, you can find some elastic straps designed to keep 2 quilts attached to one another. You can also find female and male individual snap clips that could be sewn on the TR blanket
If you want an item that can be duel purpose and attach multiple quilts check out "lock laces"
https://www.amazon.com/LACES-Elastic-Shoelace-Fastening-System/dp/B007DLVLBQ/ref=sr_1_4?ie=UTF8&qid=1513378748&sr=8-4&keywords=lock+laces
bigcranky
12-15-2017, 20:31
The sleeping bag rating was based on what temp it was when your companions found your frozen dead body in the morning.
Thank you for the best laugh I've had in months. :)
Hmmm... I've got a 50F quilt and 30F bag. Forecasted low of 18 tonight.
Unfortunately, I'm lacking a 'winter' pad.
all very interesting to me.
about the rating being rubbish..... I don't know, I feel that they are more like a point of reference. Not an absolute thing so much. IN my very limited experience with cheap synthetic bags and quilts, I'd say that whole thing based on 70 degrees being the no quilt datum that things are fairly on the mark (given the fact that 70 degrees is not my "no quilt" temperature). My 20 degree cheap synthetic bag is good for me to down to the low to mid 30's
My latest quilt is a BA Kings Canyon...I've had it for 2-3 years now and I have some experience with it down to about 45. not rated officially as far as I know but I believe specs were for approx 45 degrees. I've found that for me its good to low 50's.
When I made this post, I wasn't thinking so much of the purpose buy of two matching quilts or bags with the purpose of a layered system. I'm currently considering getting something a bit better, such as maybe an EE quilt, probably 20 degrees. But my mind is spinning on options of combining something like a 30 degree that might actually serve me better, with my Kings Canyon quilt.
Another point of consideration for me is weather to buy something different for my kids. Two of them currently have only some cheap kids bags that I would guess to be 45 degree or maybe 50 degree...so I was wondering what I might expect if I layered my kings canyon on top of theirs...
wordstew
12-16-2017, 07:46
I like the idea of a synthetic quilt on top of my down quilt to take the brunt of the wind/rain/snow/frost weather abuse to give me a layering option depending on the temp/weather.
all very interesting to me.
about the rating being rubbish..... I don't know, I feel that they are more like a point of reference. Not an absolute thing so much. IN my very limited experience with cheap synthetic bags and quilts, I'd say that whole thing based on 70 degrees being the no quilt datum that things are fairly on the mark (given the fact that 70 degrees is not my "no quilt" temperature). My 20 degree cheap synthetic bag is good for me to down to the low to mid 30's
My latest quilt is a BA Kings Canyon...I've had it for 2-3 years now and I have some experience with it down to about 45. not rated officially as far as I know but I believe specs were for approx 45 degrees. I've found that for me its good to low 50's.
When I made this post, I wasn't thinking so much of the purpose buy of two matching quilts or bags with the purpose of a layered system. I'm currently considering getting something a bit better, such as maybe an EE quilt, probably 20 degrees. But my mind is spinning on options of combining something like a 30 degree that might actually serve me better, with my Kings Canyon quilt.
Another point of consideration for me is weather to buy something different for my kids. Two of them currently have only some cheap kids bags that I would guess to be 45 degree or maybe 50 degree...so I was wondering what I might expect if I layered my kings canyon on top of theirs...
That would take up a lot lot of space in your pack. 2 synthetic bags. I can suffer hiking in bad weather but not when sleeping. Better off over bagged then under bagged.
Thom
I like the idea of a synthetic quilt on top of my down quilt to take the brunt of the wind/rain/snow/frost weather abuse to give me a layering option depending on the temp/weather.I bought quilts with this very thing in mind. I have a 40* synthetic reg/reg that goes over a 40* down short/small for the wife. A 50* synthetic long/wide and a 40* reg/reg for myself. The wife's combo shows 10* on the EE chart 20* for mine, she sleeps cold so 20* might be the actual rating for her based on the chart. Haven't gotten out in cold temps though as we don't have pads for cold atm.