Layering isn't just for clothing
Sleep system questions are a perennial on r/Ultralight. People asking for advice for what sleep system they should get want a simple answer to a deceptively complicated question. To begin with, comfort is based on perception. It is not an absolute, and can only really be determined by each individual. Next you have differences in metabolism, body size/weight, gender, what a person ate for dinner, the pad that they are sleeping on, humidity levels, what the person is wearing to bed, and on and on and on. Temperature ratings are directional, not definitive. And while there are standardized test methods (ISO 23537 for sleeping bags), there is just no way to have a simple answer that will work for everyone. (And note that there is no analogous ISO standard for quilts.)
What to do then? Simple - you've got to test things yourself. You've got to test different combinations under different condition sets, gather data, and learn about what works for you. What if you don't have time for that? Well, you revert back to fear and overkill: you end up with a 20 degree quilt/bag for a trip that most likely won't get below 40 or 50 and end up sweating yourself every night. Why? Because it might get down to 25 or 30. (See this article I wrote about probabilities and temperature estimation.) The overly conservative/overkill solution comes with additional drawbacks. In addition to sweating yourself many/most nights, you're also carrying more weight/bulk and maybe paying more.
When I was growing up in northern New England, I would leave the window open on cold nights because I enjoyed the feeling of breathing in cold, crisp air. I would heap additional blankets onto the bed and wear a hat to bed. I enjoyed the feeling of a heavy blanket set. I continue this tradition when given the chance - though the opportunities are rare in southern Texas. (The great freeze in February of 2021 was kind of fun!)
Point is layering works. The same advice I learned as a Boy Scout (wear several thin layers vs one thick one) works with sleep systems just like it does with jackets. You can combine what you're wearing to bed, with your quilt/bag, and with additional quilts/bags (yes, you can have one quilt/bag inside/on top of another), to dial your warmth in to fit the conditions. This is why I recommend testing. Test different combinations of pad, bag/quilt, and clothing at various overnight temps/conditions to learn what works for you.
Case study
In 2022 I bought a Cedar Ridge Outdoors "Helium" 40 degree quilt. I was suckered by the marketing: UL construction: 7D shell, DCF baffles, and 1000 fill power down. It was an incredible weight (272 grams), but when I took it out on its maiden voyage (temps in the high 40s) I was disappointed. It was severely anemic: 40 F was a fantasy - at least for me. Rather than sell it (what I should have done), I listened to advice from a friend of mine who had MYOG'd a down quilt. He said working with down wasn't nearly as hard as I had been led to believe. I bought some 900 FP, watched some YouTube videos, and went for it. I hung the quilt vertically for a few days and shook all the 1000 FP to one end of the baffles, then seam ripped the closure and added a bunch of 900 to the empty spaces. I ended up adding 4.5 ounces of down, and turned this anemic quilt into something with a dense/healthy 2.25" of loft. However, I only added down to the vertical baffle section on the torso. I never added any to the horizontal baffle section (the footbox), meaning that portion still had the anemic level of fill.
With 2.25" of loft, this quilt is my workhorse: it is the quilt I use on most trips. What I have discovered, however, is that when the temps get to 35 degrees my feet get cold. The rest of me will be toasty warm - just my feet will be cold. This isn't a surprise since I didn't add down to that section of the quilt. I have more down. I was contemplating adding it and estimating the weight addition when it occurred to me: why not just wear down booties over my feet when the temps get lower than 35F? The booties weigh 59 grams (~ 2 ounces.) 2 ounces was roughly what I estimated I would need to add. By going with the booties I have flexibility. I can leave them behind if the trip isn't predicted to get into the 30s, and take them when it does.
I tested this setup for the first time in January of 2025 on a night when my thermometer said it got down to 26F. I used my quilt on a Thermarest Uberlite (R = 2), on top of concrete, in my back yard. I wore the down booties as well as my Montbell lower body base layer and a Patagonia Capilene Air hoodie (now discontinued.) I wore this combination of because it is what I brought on the 10 day trip on the Ouachita Trail in November of 2024. I was testing to see if the CRO quilt paired with an Uberlite and booties would have been enough to keep me warm. I was wondering if I could have left my heavier/warmer Xtherm (R=7.3) and 20F Timmermade Conti quilt behind. To my surprise not only was I warm, but I was sweating a bit. A couple weeks later I took this same setup on a trip with the Scouts where the overnight temperature was 27. Though I didn't wear the Montbell and Patagonia garments to bed, I was quite comfortable.
Sleep System Lineup & Strategy
Not everyone can afford to have an optimized tool for every job. Over time, however, I have acquired/evolved a series of items to cover a wide gamut of conditions. I haven't tested some of these combinations yet because the opportunities in south Texas are rare. For pads, I have a Thermarest Uberlite (R=2), a Thermarest Xlite (R=4.5) and a Thermarest Xtherm (R=7.3). I only take the Xtherm for cold conditions: 25F and below. I've found that I sweat on it if the temps are above about 35F. For years the Uberlite has been my go-to for everything except cold stuff, but the Uberlite series has been plagued with manufacturing defects. As they fail Thermarest warranties them with Xlites - which is why I now own one of those as well. Once my last Uberlite fails (I had multiple sizes) it will fall out of this lineup.
For quilts, I have:
A Timmermade Alpha/Argon "overquilt" that is good by itself around 60 degrees, but is intended to be used as an extra layer on the more substantial "Conti" quilt for condensation management purposes.
A MYOG Apex quilt that is good by itself around 60 degrees. It was made as a lighter alternative to the Timmermade alpha/argon and serves the same purposes. (It is 105 grams lighter.)
The Cedar Ridge Outdoors Helium that I have modified as described above. I use this quilt from about 60F down to about 25F (when also using the down booties.) This is my workhorse and gets the most use.
A Timmermade Conti 20F "skirt quilt." I only use this when it is cold or predicted to get cold. I sweat in this quilt if the temps are above 35F, especially if paired with the Xtherm pad, so I restrict this quilt's use to cold temps. So far I've taken this down to 13F on an Xtherm and was comfortable. If paired with the Alpha/Argon overquilt or the MYOG Apex overquilt and baselayers, I'm confident with this into the single digits, maybe even to 0F.
Bottom Line
Point is when I craft my packing list for a trip, after mapping out climactic data and probabilities (see Data Not Fear), I pull on my personal test history with the various equipment choices and combinations to decide what I'm going to take. How much margin I include (to cover those low probability events) is a risk/benefit analysis I do for each trip. Then, of course, when the trip is immenent (rather than a long-term future plan), I review the short term forecasts vs. my previous plan to determine if, given the lower uncertainty accompanying actual weather forecasts, I want to tweak anything in my kit.
Hope that helps
Hike On my friends!
