Author Topic: How warm should your sleepingbag be?  (Read 1797 times)

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Offline davidbonn

How warm should your sleepingbag be?
« on: March 30, 2024, 10:48:42 am »
How warm (in terms of "comfort rating") should a sleeping bag be for typical three-season bicycle travel?

This is also made much more complicated because different manufacturers use different techniques to determine the "comfort ratings" they use on their products.  So it is basically impossible to make a rational comparison between brands based just on their rating.  A better approach might be to compare fill weight between bags of similar design and size, though even there it is pretty easy to get lost in the weeds.

Another complicating factor is that very few sleeping bags provide significant insulation underneath the sleeper.  For that you'll need some kind of insulated pad.  Depending on your situation you may be losing much more heat by conduction with the cold ground than into the surrounding air.

If you haven't already noticed, people are all very different.  Some might shiver the night away under a fluffy down comforter in a room that is a smidgen below 70F, while others will wrap themselves in an old horse blanket and snore all night on an ice floe.  On top of that, what you ate for dinner and how hard you are exercising can effect how warm you sleep in often bewildering and unpredictable ways.

Sleeping in a tent, in particular sleeping in a pretty small tent, will on the average be much warmer (easily 10-15 degrees F) than without a tent.  Similarly, a small bivy sack can make a pretty dramatic difference.

Blatant product plug:  I use and like this inexpensive and light bivy sack when tarp camping:

https://bivysack.com/shop/ols/products/bivysack-standard-zip-regular-length-c1635e9e-1703-4bd1-880c-74a89e55fa7c

Finally, careful campsite selection and an awareness of microclimates can make a dramatic difference in how warm you sleep.  Often times locations even a few dozen feet apart will have dramatic temperature differences.  As only one example, cold air sinks and locations close to streams and lakes can be 10F colder than a location a short distance uphill.  This can also work for you the other way on a hot, muggy night.

It is important to remember that you'll be just as uncomfortable sleeping too hot as sleeping too cold.  And you can always wear warm clothes to bed on a super chilly night.

For myself, I usually use a down quilt rated at about 30F for most of my summer backpacking and 3-season bicycle travel.  That means there are a few somewhat chilly nights where I am wearing a lot of clothes, but generally this approach provides the most comfortable sleep.  I'm usually in that bivy sack which overall keeps me nice and toasty to about 20F.  Also, for me, down is far better product both from a functional standpoint and value for money.  A well-cared for down bag or quilt can easily last a dozen years of hard use.

My personal observation is that most backpackers and bicycle tourists are carrying a too warm and too heavy and too expensive sleeping bag.

What works for you?  And what would you like to use?  I think the Zen Bivy products are intriguing (if terribly expensive).

Offline jamawani

Re: How warm should your sleepingbag be?
« Reply #1 on: March 30, 2024, 12:29:10 pm »
As you say there are many additional factors besides sleeping bag ratings.
I usually use a lightweight summer sleeping bag - even in the West.
I also sleep in a tent with a pad under me. The pad is big for warmth.

There are three small, lightweight items that make a huge difference:
1. Wool socks
2. Polypro glove liners
3. Polartec cap

(These also help if you get caught in a cold snap or get wet and deeply chilled.)

Sometimes, I put them on beforehand if I know it's going to be chilly.
Other times I have them within reach, if needed.

Whether or not you actually lose more heat from your extremities,
you often feel it there and it keeps you from sleeping well.

Offline jwrushman

Re: How warm should your sleepingbag be?
« Reply #2 on: March 30, 2024, 06:54:02 pm »
The best advice I have is to try out whatever you're going to be using in your backyard as many times as you can. On warm nights . Cold nights. On rainy nights. The more that you practice, the more comfortable you'll be with your equipment and know what works and what doesn't work. And you'll be much more adept at setting up camp and taking it down. At what temperature do you need a balaclava? At temperature do you need down booties? Long underwear? Thin sleep pad versus thicker?

Offline LouMelini

Re: How warm should your sleepingbag be?
« Reply #3 on: March 30, 2024, 10:11:09 pm »
There are a lot of variables when it comes to sleeping systems (bag and pad) as Davidbonn stated. He said "most backpackers and bicycle tourists are carrying a too warm and too heavy and too expensive sleeping bag". I will focus on the "too expensive" Good quality bags will be expensive. However these bags will probably have a true temperature rating, be light-weight due to a higher quality of down (my preference), and last for a long time making the initial purchase price seem cheap over the lifetime of the bag. Julie and I have had a sleeping bag for the two of use since our marriage nearly 42 years ago. It is a Marmot, down (not sure what rating of down), with a gore-tex shell. It is no longer as warm as it was when we purchased it. Most of our outdoor travel has occurred since 2004 when our youngest son graduated high school. The Marmot bag has been on most of our 16,000 miles of bike travel we have done (maybe all). That bag has also been with us for most of our backpack trips that include an Appalachian Trail thru-hike (we used our Western Mountaineering for the final 400 miles). The Marmot bag weighs 3 pounds (for both of us) and cost $200-300 in 1982 (I don't remember the exact price). As you can imagine, we have had cold weather at times (near 20) in our travels. As Jamawani astutely stated we keep clean socks and beanies handy, and lately (due to our age) long underwear (top and bottom). I will keep in mind to use the glove liners in the future. We also have a Western Mountaineering bag that is warmer for outings that we know will be consistently near or below freezing. This bag is "only" 15 years old and cost about $400. Both of our sleeping bags open up into one large quilt. We purchased "couplers" that zip onto the sleeping bags underneath us that keep our sleeping pads from sliding. The couplers are a thin fabric that keeps the system intact and reduces some heat loss. We have used a variety of Thermarest products for sleeping pads over the years. My current favorite is the Neoair Xlite NXT for both comfort and warmth. We always sleep in a tent.

Offline John Nelson

Re: How warm should your sleepingbag be?
« Reply #4 on: March 31, 2024, 12:09:58 am »
It is no longer as warm as it was when we purchased it.

I’ve been surprised at how much warmth is restored to a down bag by a good washing.

Offline davidbonn

Re: How warm should your sleepingbag be?
« Reply #5 on: March 31, 2024, 09:39:00 am »
Thanks for all of the comments!

I too also carry a fleece hat and have warm dry socks and liner gloves for camp and possibly in the sleeping bag if it is cold enough.  Also I recommend having a slightly oversized fleece hat that you can at least pull over your eyes, both to keep you that much warmer and to make it easier to sleep someplace with bright lights.

Some bag manufacturers (Feathered Friends for sure and I think Western Mountaineering) can add down to your old sleeping bag to somewhat restore it. 

Also, to clarify, when I talked about "too expensive" what I specifically meant was that sleeping bags, all other things being equal, are purchased by the pound.  So on the average a heavier sleeping bag of the same manufacture will cost proportionally more than a lighter one.  This is largely because down fill is usually the most expensive part of a bag and more down will translate into more cost.  Very light bags can use a sewn-through construction rather than with baffles, which is also much less expensive and lighter.  So purchasing a total overkill sleeping bag for your planned use will cause you to spend money you never needed to spend.

A well-cared-for down sleeping bag can last decades.  Usually for me the first failure points that you really can't do much about are the zippers.  One advantage of quilts is that often they do not have zippers and the zippers they have aren't functionally critical to a warm night's sleep most of the time.

I've never owned a synthetic fill sleeping bag that managed to survive more than two or three years of heavy use.
« Last Edit: March 31, 2024, 01:09:57 pm by davidbonn »

Offline Jocycleph

Re: How warm should your sleepingbag be?
« Reply #6 on: April 01, 2024, 10:10:47 pm »
The best advice I have is to try out whatever you're going to be using in your backyard as many times as you can. On warm nights . Cold nights. On rainy nights. The more that you practice, the more comfortable you'll be with your equipment and know what works and what doesn't work. And you'll be much more adept at setting up camp and taking it down. At what temperature do you need a balaclava? At temperature do you need down booties? Long underwear? Thin sleep pad versus thicker?

Your approach to testing gear in various conditions is spot-on, @jwrushman. It’s an excellent strategy for grasping how your gear functions across a range of temperatures and climatic variations. My choice is a multi-layered sleeping bag that allows for layer removal. This provides significant adaptability and the ability to tailor it to the prevailing weather. It also serves as a useful hint that comfort levels differ greatly among individuals, and what suits one might not suit another. Ultimately, the secret lies in discovering the perfect mix of gear and attire that suits you best, which comes with trial and learning.

Offline hikerjer

Re: How warm should your sleepingbag be?
« Reply #7 on: April 02, 2024, 06:09:59 pm »
I use a 40 degree down mummy bag from Marmot. Keeps me warm nearly all the time. On the few nights it doesn't, I wear extra clothes to bed. Never really been cold during summer tours.

Offline LouMelini

Re: How warm should your sleepingbag be?
« Reply #8 on: April 02, 2024, 09:37:47 pm »
John: Just to be clear, the bag has been washed (down specific soap) many times. It comes out warmer but the bag probably needs more down.

Offline froze

Re: How warm should your sleepingbag be?
« Reply #9 on: April 07, 2024, 10:03:59 pm »
I only do bike camping in the warmer season, so I travel with a 40-degree Alps Mountaineering Fusion bag.

Bags are supposedly rated 10 degrees colder than they can actually be good at. 

The bag I have is a combination down top and a synthetic bottom, kind of a goofy design in that there are no zippers, it has T fasteners?!  But I got stuck in a rain storm and the outside temp dropped to 40 degrees, I put on all my clothes, and was still too cold for comfort.  So, when I got home, I ordered a Sea To Summit Reactor Fleece Sleeping Bag Liner to protect the bag, but also to add a bit of warmth, which they said 15 degrees added to whatever bag but it was probably closer to 8 to 10, but at least if it gets too warm to be in the bag I can just sleep in the Reactor liner by itself.

Basically how warm your bag should be is figure on it being 10 degrees warmer than the coldest weather you are expected to sleep in, so if 40 degrees is the coldest, like I experienced, then you should have a bag rated for 30 degrees.

Offline davidbonn

Re: How warm should your sleepingbag be?
« Reply #10 on: April 08, 2024, 09:21:38 am »
...
Basically how warm your bag should be is figure on it being 10 degrees warmer than the coldest weather you are expected to sleep in, so if 40 degrees is the coldest, like I experienced, then you should have a bag rated for 30 degrees.

That depends a lot on the person in the bag and the manufacturer.  It is very hard to make a generalization like that.

I have a Feathered Friends Widgeon that is rated to -10F that I use for extreme cold-weather trips.  I've been toasty down to -25F in that bag.

For a long time I was a big Western Mountaineering fan and found their bags were typically good to 5-10 degrees (F) below their comfort rating.

I can't say if that is because FF and WM under-rate their bags (although there is some evidence for that, mainly if you look at weight comparisons for their bags and comfort rating compared to other brands) or because I have a metabolism like a furnace.

Offline froze

Re: How warm should your sleepingbag be?
« Reply #11 on: April 08, 2024, 03:24:16 pm »
...
Basically how warm your bag should be is figure on it being 10 degrees warmer than the coldest weather you are expected to sleep in, so if 40 degrees is the coldest, like I experienced, then you should have a bag rated for 30 degrees.

That depends a lot on the person in the bag and the manufacturer.  It is very hard to make a generalization like that.


I have a Feathered Friends Widgeon that is rated to -10F that I use for extreme cold-weather trips.  I've been toasty down to -25F in that bag.

For a long time I was a big Western Mountaineering fan and found their bags were typically good to 5-10 degrees (F) below their comfort rating.

I can't say if that is because FF and WM under-rate their bags (although there is some evidence for that, mainly if you look at weight comparisons for their bags and comfort rating compared to other brands) or because I have a metabolism like a furnace.

I have a fairly high metabolism for not gaining much weight, but not for keeping me warm, but I'm not cold all the time either like my wife.  I can be riding my bike at below 40 degrees and never warm up like other riders I know of.  But those numbers I gave are just industry standard, but sure, each person is different, as is each bag, or quilt.

Offline davidbonn

Re: How warm should your sleepingbag be?
« Reply #12 on: April 10, 2024, 11:35:27 am »
Wow, you learn something new every day.

I didn't know there was an actual ISO standard for measuring the comfort rating of sleeping bags.

You can tell if the product is ISO tested because they will give both a "Temperature Rating" and a somewhat higher "Comfort Rating".  The "Temperature Rating" is a fairly good estimate of how cold you can comfortably sleep in the bag if you are a warm sleeper, and the "Comfort Rating" is a fairly good estimate of how cold you can comfortably sleep in the bag if you are a cold sleeper.

Unfortunately, none of the brands of sleeping gear I have purchased in the last thirty years are ISO tested.  From reading between the lines (mostly comparing down fill weights) I can estimate that, on the average, most of them are very conservative on their ratings and they tend to err towards estimating how a cold sleeper will feel sleeping in their products rather than a warm sleeper.

Probably the most conservative of the brands is Feathered Friends, with Western Mountaineering being close behind them.  On the other hand, jacksrbetter ( https://jacksrbetter.com ) are generously optimistic in their temperature ratings.

Offline froze

Re: How warm should your sleepingbag be?
« Reply #13 on: April 10, 2024, 05:10:26 pm »
Everything that I've read said quilts are rated exactly, whereas sleeping bags are 10 degrees cooler than rated meaning if it's a 40-degree bag like mine, it will be comfortable down to 50.

Of course, there is always a high possibility that not all bags will be rated correctly, our problem is we can't determine that unless we buy all the bags made and test them for ourselves which is a bit impractical. :o

In the bag I have I don't think 50 is correct, probably closer to 60 because when it got below 45 I had my Thermo Reactor liner in, and all my clothes on including my jacket!  So at 50 I probably would have still had most of my clothes on!  Granted, I have a cheap bag I got on sale for about $60 from $145, but it's always on sale!  LOL!!  But it's a lightweight bag, stuffs small, so it's ok, it will do till I decide I need a better bag, I've used it many times, and it's holding up just fine, so it could be a while before I need another.

Offline ray b

Re: How warm should your sleepingbag be?
« Reply #14 on: April 14, 2024, 09:13:05 pm »
What Froze said
(except quilts also carry the same ratings as bags.)

Cpmfort usually runs 10-15 degrees above the rating of the bag or quilt. The rated temperature is one at which the average person will not be comfortable, but also will not be hypothermic.

I carry an Enlightened Equipment 40 deg quilt summer; 20 deg quilt summers in the mountains, or spring and fall at <5000 feet; and I move to sleeping bags of 5 deg and -20 deg F fall and winter and spring, as needed depending on predicted conditions. And yes, I've used the 5 degree bag in August in the mountains. Try to plan ahead.

If you have to own one bag for biking - 20 deg rating is best. You can always thrown in a liner. And remember:
  • Tents add about 10 deg of insulation to comfort range.
  • And yes, Jay Petervary races without a sleeping pad in the summer. Mere mortals like me find the thermal benefits of staying off the ground worthwhile. The thermal rating on your pad should be in line with your bag.
  • Jamawani's hat might add a good 5-10 deg F improvement in tolerance.

As with many things - the adventure comes from getting out with the equipment you have and forming your own opinion.
Have fun.
« Last Edit: April 14, 2024, 09:17:34 pm by ray b »
“A good man always knows his limitations.”