Cold weather sleep system

Last weekend I wa sout dor an overnighter and the forecasted temperature of 5f turned out to be -13f (it was about -5f in the tent), I used a 20f bag with down Parka, trousers and booties which kept me toasty warm, the combined total of the lot had about 35oz of down.

I tend to bring enough bag for the expected low temperature, and rely of any personal insulation like a down parka for when the weatherguessers screw up and underestimate how low it will really be. In NH things can go from 0F to -20F or more in the space of a day.

As to what kind of overbag or quilt would work, I'd start with researching the fill weight of your current bag and a single bag for the intended temperature, then get an overbag with enough fill to make up the difference. I've found a good quilt works perfectly for this.

Also, adding a VBL top or hoody is a lightweight way to add extra warmth. Take a look at RBH Design's cuben VBL top.

I am with Don on this, I should of mentioned that I was only using this kit as I had loaned my winter bag out to a buddy.

You are going about it one way: with these clothes, what bag do i need For this temp?

That is a way to do it. Another way is to start with your bag and the temperature for which it is comfortable and then add in the extra insulation from the clothes…

If i weren't sure about the clothes and was comfortable with my bag, i would start out using way number two…

There have been a lot of posts in the past about insulation ratings, clo, of clothing… You could search posts by Richard Nilsen and find these. I don't have access to the little graphs right now, but i think his tables would indicate your clothes would be about 15° extra insulation. Or there abouts. A little more if you wear both tops. I remember this estimation because i made 3 oz. Primaloft pants and, according to his scale, they should add 5 degrees. I am making a bit of a guess about your top. I used his scale as a rule of thumb. There has been variation over time in the insulation value assigned to different garments…

Anyway, I would start with the temp you use your bag and then try to add your clothes. The clothes you listed aren't very heavy and might not add a lot of warmth… They might be well considered 'extra' to deal with changes in temp, as was suggested above.

A way I tried to estimate clothing and bag was to pack clothes I thought I would be comfortable in at rest, not asleep but not working, and not in the bag… Then pack a quilt that was warm enough to keep me comfortable as my body slowed down and cooled during sleep.

That is a way I went about it… Whatever i decided doesn't matter because your conditions are different, I am sure.

PS – I don't mean to be snarky. I just mean you likely can't simply copy my choices into your use… Humidity, for instance, can make a big difference. Anyway, hope the comments about the strategies for finding your answer are helpful!

Thanks group. I may have to revist the top bag idea.

Tanner, I agree that option two would be the better way to go. Thing is I already own a 25F degree bag and the above insulation. I'm trying to get into colder temps and would like to be able to use some of the pieces I already own. There is a pretty big jump in bulk from say a 0F to -20 bag and I was hoping to bridge the gap with some insulation I already own.

Hi Ben,

Make sure to try out whatever system you go with close to home or your car (or have some other backup plan) as freezing your nuts off could be down right dangerous.

When I pushed my system last weekend I brought 4 chemical hand warmer with me (I used two) and also had a 1ltr bottle with hot water ready to go if needs be, also there was 3 of us in tent so the combined body heat helped also.

If you are in a situation in winter where you are freezing you would pay anything to be warm, I have been in that situation and went straight out and bought the best winter bag I could get my hands on for the next trip.

Cheers,

Stephen

At the temps you are looking at, I figure you might want more clothing…? More clothing to be comfortable around camp. This will, of course, allow you to stretch the sleeping bag further….

At whatever temp, you need however much insulation. Put more of it into clothing or more of it into a bag/quilt. Which of these is more efficient is your question, I figure. This is why I mentioned the strategy I used to make my determination..

It may be more efficient weight-wise to carry a warmer bag with lighter clothing and then plan to hop in the bag to keep warm. Sounds like you prefer this. I spend time sitting out standing because I like to take pictures. So, I weighted my insulation toward clothing.

I may be restating a thing you already have on mind, but first decide how you like to carry your insulation and how you plan to use it and then how much you need..? Obviously, you will have to add insulation and, for me, I would add more clothing to your 25° bag…

I am not sure I would add enough clothing to make that bag comfortable at -20. Not because I advise against it but because I have no experience with sleeping in -20 to 0. I think I might want both more clothing and a warmer bag… So, for me, Stephen's advice is good.

I don't mean I would buy another bag. I would also follow Don's advice for the over bag.

PS
Since the temps you are considering are a good bit colder, it might be good to review your sleeping pad. Your current pad set up might be fine or it might benefit from an upgrade.

Ben, you're on teh right track with insulated clothing to extend your sleeping bag's temperature range.

I've done the same thing with my WM Megalite (conservatively tated to 30 F.) and was fine at 15 F.

The reason your idea is so good is because your insulated clothes ("mid layer") can also serve to keep you warm while walking around in terribly cold weather. Sometimes even the weatherman/lady can get it wrong and then we desperately need more clothing.

So think of your insulated clothing solution as "multi-use" items.

The title of this thread is "cold weather sleep system." Yet nowhere does anyone mention ground pad. Your pad is at least as important as any materials placed over your body. Doubling the thickness of a ccf pad would have quite a dramatic effect on sleep warmth. Remember that the (very expensive) down on which you are sleeping in your sleeping bag provide almost zero insulation for your underside.

Paul you're right. I should have mentioned I have an X-therm and Ridgerest combo. My understanding is that EIN ratings assume an R5 pad, which I think the above combo is close to.