The Thermarest Neoair 4-season is listed at ONE ounce more than the 3-season version but doubles the R-value to an amazing 4.9 due to 3 sheets of reflective material compared to the 3-season's 1 sheet. Now, if I were to use this pad in summer, granted in the Adirondacks where it can easily hit 30 or 40 but is usually in the 50s at night, could I ditch my sleeping bag and use just a bivy and my clothes? Instead of a 20oz crap bag that requires a fleece anyway, why not a slightly heavier fleece, 12oz vs 7oz, leggings at 6oz, wear my socks to sleep, etc to add insulation and rely on the bivy to provide a shell? Has anyone ever done this in the conditions I am speaking of? I would save weight (10-16oz depending on which bag I use in the summer) and make my system more versatile, adding a bag in the shoulder seasons but relying on clothes for the summer. oh and I always use a silk liner, with or without a bag, so I could throw that in for summer use as well.

Greg, sorry no-one has replied. I don't have the exact combination of items you described but I have tried the similar idea of insulated clothing and no sleeping bag, about 30 years ago and it didn't work out for me so not repeated. I found I was at the same time too warm in places and yet cold in places, the proportion of clothing that worked when moving didn't work when I was asleep. Now I think I know the reason why is that the blood system pumping when active moves heat around the body, away from heat-generating parts and into other parts, a kind of equalizing effect. When asleep though the blood is much less pumping and body behaves completely differently and so heat-generating parts are not having the same opportunity to pump their heat away so they begin to get too-warm and the other parts aren't getting as much warm blood in to them so not as warm. The sleeping bag or duvet over loose clothing basically gets that radiating heat easily off the body and moves it around the bag which traps the heat, doing via air circulation similar to what blood does when active. I've found since then using clothing to boost a bag's insulation has less of an effect so I now simply focus on a sleeping bag with plenty of insulation for the general temperature and augment with internal and external insulation to tune to the day.

I don't know the degree your bivy will act to trap warm air, I think a bivy is a thin shell so via conduction it will tend to lose its heat easily (its not insulating).

Have you tried some safe experimentation in your house in some season, open the bedroom windows or something when its the right temps outside and just sleep on your bed in some ideas of clothing and see how you sleep???

Also every person has a different balance of heat production awake/sleep, different distribution of body-fat around the body, and different muscle/fat proportion so it is hard to extrapolate between people. FYI when I'm active I need less clothes than most others, when I'm asleep I need warmer bedding than most others so I figure you have to learn this for yourself.

My 2cents anyway.

Edit - additional - remember these high R-value Thermarests are still based on thin outer fabric, think about your Plan-B if there is a mat leakage. I thought about that for last 2 winters and I've decided to go for two mats, a Neoair small I got in a sale as its now discontinued and my old Prolite 4, I'm going to glue to velcro to these and have the Neoair over the Prolite. Will report conclusion probably towards end of this year.

Edited by nigelhealy on 03/24/2012 17:35:52 MDT.

+1 Nigel's suggestion to do some backyard testing ... or at least in some situation where you have a bailout option.

Not so sure that the 4 season neo will make a big difference vs the ordinary neo for northern summer use with warm days and cool nights. The ground will still be relatively warm when you put the pad down and the insulation value of the pad will slow its rate of cooling.

Please report your results and perceptions paying close attention to where you feel chilled and from what direction (if you do).

I'm not inclined to be as worried about the thinness of the neoair's skin. I've used neoairs since soon after they were introduced without developing leaks and I'm not extraordinarily careful with it (but it's always on some sort of groundcloth).

Thinness - which Neoair, the Xtherm or the All Season? The All Season has been out for something like a year now and chances of any bugs to be worked out, the newer Xtherm, I'm guessing from the context of weight Xtherm/Xlite , is only just barely coming out now so unless there is an urgent trip, suggest giving it 6 months for bugs to be worked out. All Season has a 70d bottom 75d top, the Xtherm is I think 30d bottom 70d top so they got some of that weight saving from thinner fabric. The Neoair original has 30d top and bottom.

In the context that someone is using an original Neoair, by definition of its lower R value, *if* it were to fail its generally warmer conditions and/or someone has warmer sleeping bag, in the context of the high R-value newer mats, the context is much more cooler and/or little other insulation, so *IF* the mat were to fail the consequences are more significant. That is what is I referring to, not just probability but impact. Now in *this* thread, generally clothing compresses less than say a down sleeping bag, so more tolerant of mat failure?

As Xtherm is coming out in early April, 6 months later is October so that's a good time for the (then) cooler seasons. I was thinking of getting an Xtherm too, or the Xlite Woman's but I was hoping for these to get into owner's hands first plus I bought an Xlite small in January and immediatelyreturned it due to excessive taper, not something you'd seen on the likes of say Prolite short.

Its been too warm in New Jersey the past month to try it out! But I get the idea that clothing can have more hot/cold spots compared to a bag. Perhaps then I would just need a quilt, as the high R value pad should be plenty for summer and shoulder use with a light quilt. I used a quilt for a few nights on a Z-lite and never felt cold on my back. In any case, this idea would be for old school hardcore fast and light summit assaults in the northeast, where one night of being slightly uncomfortable might be worth the weight savings. As it is, I use a very generous "40 deg." bag in the summer and Ive always been fine. Heck I used it in Yosemite last Sept. at 9000 ft, with two fleeces on instead of one!

Thanks all, ill let you know what I find if it ever gets cool enough to warrant insulation!

The answer can be calculated from two of Richard Nisley's great posts:
http://www.backpackinglight.com/cgi-bin/backpackinglight/xdpy/forum_thread/9378/index.html
The graph in this thread says that sleeping at 50F you'll need a clo of about 4.25. I think this is based on thermally neutral -- you are neither gaining or losing heat. To get to that clo, you need what he calls the R1mid + DJ= R1 hoody + long supplex pant +
socks + a really warm DOWN JACKET!
A 300 weight fleece would give you a clo of 0.92, not nearly enough,
http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=18950

Now, would you survive the night? Yes. You would probably be rather uncomfortable though.

Walter thanks for the maths.
I don't see the need to not have a sleeping bag. A bag for 45F is 12oz, compresses to about 2L, and you then tune it with some clothing and your liner to handle a bit lower temps. Is 12oz worth a bad night sleep? A 30F bag is 20oz, and compresses to about 3L.

I'd say the Neoair All Season makes more viable to have lighter kit into colder temperatures but not do the opposite of lightening summer kit.

Maybe a down bag has the attributes you listed, but certainly not a synthetic. Can't afford down at the moment, nor do I want to deal with the issues (cleanliness and dryness aint exactly my thing).

I think there's a small but real chance you would very much enjoy not having a sleeping bag. I spent several summers outside or under a tarp in temperatures 30 to 60F sleeping in my clothes and a silk liner and I really liked ditching that lump from my pack.

On the coldest nights, I slept on either a 3/4 RidgeRest and my pack or a full-length Therm-A-Rest self-inflator. I wore a 200gram wool top, poly t-shirt and tights, thick wool socks, a stocking cap, rain or sun pants if I had them, rain jacket, and running shorts, and slept in a cheapo thicker-weight silk bag liner (probably more warm than a thin one but less warm than thin fleece).

HOWEVER:
--The 30-35 degree nights were rare, and I was cold when I woke up. Most nights I knew were going to be above 40.
--I am a very warm sleeper, and had tested my system out down to 40 before committing to it on a trip. I was the only one who practiced this system out of a guide staff of around 70.
--On any trip below 40, I think a dedicated sleeping bag is a good idea, and I did not hesitate to bring one along for early-season trips with low daytime temperatures.
--It is debatable whether you will save weight. I did this because I only owned and could only afford a cheap 20 degree bag. If you could get a warmer weather bag, you could maybe leave some of that clothing at home.
--***You mention cost as a limiting factor. It shouldn't be, if you avoid spending so much money on your sleeping pad. Get a RidgeRest or something and spend the ~$100 you save on or toward a sleeping bag.

@Ryan: Its not so much the cost but the fact that I'll be quite dirty each day from doing trail crew work, and I know the cheap Lafuma bag I have now is gonna bust before the end of the summer. I am looking at some light sleeping bags, its just hard to find a non-down bag under 2 pounds in a long.

Edited by gregpphoto on 03/26/2012 22:35:49 MDT.

Greg, makes a lot more sense in terms of your gear age and context.
What is the risk your old dirty clothing could ruin a fairly expensive new Neoair All Season?
Does this call for some MYOG, stitch a layer on your old bag to make it last longer? You know we use those ideas with seat covers from fabric to stretch an old couch....
Your clothing, don't wear it all but place inside a sandwich of layer in a MYOG bag-shape something??? (sounds in my mind a bad idea just offering in case others think a good idea).

The general view from many in this thread is using clothing to boost a sleeping bag will work but using clothing instead of a sleeping bag won't kill you just lead to cold waking and feel bad the next day. So basically you're only missing adding some insulation to an all-bag bag-shape "thing".

Good on ya for doing the trail work. I've done a little, but I have known many people who have done this all summer as well. As far as I know, they all brought sleeping bags, some synthetic and some down (Carhartts all day, through lakes and swamps and rock, then those doff those and climb into a light bag for the night). I think with your silk liner and a bit of pre-bedtime wash-up, you shouldn't be too hard on a bag. Maybe a top quilt would be best, since you won't grind any grit into it with your weight and you won't dirty it as much with your head/hair.

Whatever you end up with, enjoy all your nights out!

Greg, I have the NeoAir 4 Season and it's an awesome pad, definitely warm. You feel the warmth radiating from it when you lay down, and the thickness and durability is rad.

I don't think you could get by without some barrier trapping your heat. I'll be traveling to Europe this fall and plan on buying one of these: Thermolite Mummy Liner.

Combined with the NeoAir 4 season, a bivy sack, this liner, and all of your clothes, you might be able to get by in temps above 40. That's probably pushing it though, depending on the clothes you're wearing. But it's worth a try.

I didn't make the connection that you were thinking of doing this for your SCA trail work. Please don't. Your body will benefit greatly from sleeping comfortably. I doubt your sleeping bag or quilt will get that dirty, but if it does, it's worth it. If you're really worried and want to save weight, then bring a set of silk sleeping clothes.