WM summerlite vs ultralite for temps down to 20F

I own a Marmot Hydrogen which is rated at 30*, similar to the WM Summerlite, and I also own the WM Ultralite Super. IMHO if I were to sleep in the layers you listed I would be able to push the 30* rated bag to at least the temp range of the Ultralite if not lower. If used with a light bivy I would likely be able to push this system to 15* or lower, but please note that I'm a warm sleeper. The additional width in cut of the WM Summerlite and Marmot Hydrogen offer adequate room for said layers if user is average to slim in body type.

When pushing the temp range of any bag the choice in pad is also critical to ones overall comfort, again IMHO.

Let us know what you decide to try and how the system works for you.

I have the Ultralite (loft 5") and have slept in the Megalite, which has the same loft as the Summerlite at 4". The Megalite has a top draft half-collar whereas the Summerlite has a full draft tube down the zipper so its probably a wash in added comfort for those features with maybe a slight edge to the Summerlite.

Essentially, you're trying to replace about 1" of loft by carrying the SL over the UL. Looking at your list of added clothing and liner, I'm fairly sure that I would be fine in the Summerlite down to 20 degrees. The question is would you? Do you sleep warm or cold? Are you generally ok in a bag with 5" loft down to 20 degrees? If the answer is yes, you'll probably do fine with the added clothing you list and the SL bag.

To examine your question much more in depth (from a standpoint of weight and functionality) we need to look at what you really gain with your proposed sleep system. I would say very little. I'm sure you'll carry the beanie and UL inner jacket regardless of which bag you use since you'll want those items around camp. As for the silk liner and down pants, you want to carry those to boost the temp rating of the SL bag down to 20 degrees. The weight added (5-6oz or so for the liner, 6.7oz for the pants- total 12 oz or so) will probably put you over the 29 oz. weight of the UL bag alone. One could argue that the down pants give you a little more flexibility around camp but at temps around freezing you're not likely to need them (remember that you're really not facing coldest temps until very early morning) so I think the effectiveness of this system is limited in temps below freezing.

By carrying the SL you will certainly gain weight savings when you expect temp lows above freezing, when you can leave the liner and down pants at home. On the other side of that coin, the UL give you more flexibility for temps below 20 degrees by adding the pants and possibly the liner.

I would look at the equation from the standpoint of hiking conditions you will be most likely to face. If nighttime lows will be at or above the freezing mark frequently during your hikes, I'd say go with the Summerlite. If you will be spending a good amount of time in conditions colder than this, the Ultralite would be my choice.

I apologize for the lengthy reply but its often best to temper your gear choices with consideration to the conditions most likely encountered and consider options from all angles. Unless, of course, you have bottomless pockets in which case you simply buy both bags!

It depends on your metabolism. If you want to be "warm, not just comfortably cool," then you should buy the Ultralite Super, just to be sure. If you're a fairly warm sleeper, the Summerlite and the clothes you mentioned would probably keep you "warm" down to at least 20-25 and comfortably cool down to probably 20. For myself, I am not a warm sleeper and I can only expect to be warm even in a WM bag with a couple layers of clothing on, at the bottom of the bag's temperature rating like that. So I personally don't like bringing a sleeping bag that is not warm enough, even if I think I have enough insulating clothing to supplement.

Also, using simple insulating clothing and an adequately rated sleeping bag is much more lightweight than bringing extra clothing and an inadequately rated sleeping bag.

To answer your immediate question: Yes, with all that extra insulation you listed, I think you'd be fine down to zero, assuming you could get the Summerlite zipped and still move. You've only got 59 inches of shoulder girth in there to start with. Compressed loft does not add much warmth. That said………..

Fact: You want to be warm at 20°

Fact: The Aplinlite is just a wider-cut version of the Ultralite (64" vs 59"). All other features are either identical (collars, loft) or proportional to the added girth (fill and total weights, stuffed size) .

Assumed: a 59 inch shoulder girth is adequate room for you AND your insulating jacket to move around comfortably without compressing its loft. BE SURE THAT'S RIGHT BEFORE YOU BUY. Try them at the store.

Assumed: You are going to see a significant number of 20° nights.
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I'd recommend either of these two WM bags: the Ultralite or the Apache MF (multifiber). The Apache takes you to 15° and adds the MF shell, which could be a benefit for tarp users or those who like to cowboy-camp.

I've had a MF bag for 10 years and love its wind blocking and water resistant MF shell. In fact, my wife and I have a pair of Sycamore MF bags (25°) and I use mine for PCT section hikes each August or September.

Note that with the exception of the Ultralite and the Apache MF and GWS bags, all of WM's bags for 20° and below have shoulder girths in excess of 60 inches. There has to be a good reason for that.

At 5'9" and 185 pounds, I've found the 59" girth too confining for my rolly-polly sleeping style. If that weren't true, I'd be asking the same questions you are, and would buy the Summerlite while automatically including my Patagonia Micropuff pullover and a pair of mid-weight merino wool bottoms to my pack every time.

I just wanted to second Russell's thoughtful response. Every piece of gear we carry is (or should be) based on our personal needs and expectations. Your metabolism could be vastly different than other folks, and so forth.

Carrying the silk liner to add warmth to the SL would bring weight to 1lb 8oz. The UL weighs 1lb 10oz. If I were faced w/ carry the liner plus SL or just the UL, I'd personally probably opt for the UL, esp. since you want to make sure you sleep warm. A VBL layer might be an option when you know it'll be cold(er). Not having a side-block baffle would allow you to shift down to bottom and sleep cooler if necessary. It really depends on the conditions you expect to find yourself in the majority of the time. What will temps be like on, say, 75% of your trips?

Great responses… really given me some food for thought.

Ideally I would get both, but sadly that isn't going to happen any time soon!

I was originally planning on getting the UL, but was thinking that on many of my trips the lowest temperatures would be in the range 30-35F over night. Some trips I take the temps might dip to 25F and occasionally as low as 20F, so I was wondering whether I could "get away" with the summerlite.

As Russell points out, for temperatures consistently below freezing, using the SL plus clothing isn't going to save you any weight. But you would save weight for above-freezing conditions and would probably sleep more comfortably when it was warmer.

My logic says buy the summerlite, but buying the ultralite would make me feel more secure. I think it comes down to the fact that I haven't slept in extra clothing layers before. The idea of sleeping comfortably in temperatures below a sleeping bag's rating is pretty foreign to me.

I suspect that I will end up buying the ultralite (to be safe) and then deciding a year down the track that it is unnecessary and selling it to buy the summerlite. Even though I suspect this is what will happen, I can't quite convince myself to pull the trigger on the summerlite now and skip the intermediate step.

D'oh!

I probably should have mentioned that I generally take a silk liner in order to help keep my bag clean. So I would probably take it along with the UL too. I really doubt that it gives me more than a 2-3F boost to the bag, so it's not a very effective way of increasing warmth. It's pretty much just to protect the sleeping bag.

Do you guys not use a liner? Perhaps that's something I should think about ditching…

Hey Ashley- I think you're doing the right thing with the UL. As someone once mentioned to me, if you're wondering if something is "enough," it's probably not. On an experimental basis, you could take your UL on trips and shift more down to the bottom "making it" a 35 degree–and letting you play with the clothing layers that work best for you, while knowing you've got a warm bag to back you up.

I think the silk liner bag is in large part a personal preference thing (though what isn't, really?). One way I've kept pack weight down is by wearing my lightest baselayer to bed for the cleanliness factor. Keeps that five ounces or so out of the pack. But it seems like even on this site I've seen a number of people who use liners?