Prior to spending 8 days in the North of China, to hike on a few of the derelict sections of The Great Wall and for which blog posts can be found in the 'Sleeping with a Million Ghosts' series, I wanted to ensure that the sleeping equipment I was taking would keep me sufficiently warm at night. I had decided on not taking a tent, it would be difficult to pitch and add considerably more weight to my already heavy backpack. So just a sleeping bag inside a waterproof bivvy should do as I would be able to sleep in the deserted Watch Towers should there be heavy rain or snow. The issue was how to test this out before I went and luckily the coldest day of the year, of in fact the past few years, presented me with an opportunity. In my back garden ! The, what turned out to be accurate, forecast was for the overnight conditions to be -5C plus windchill taking it to around -6C and dry with light winds. Then by sleeping on the concrete path to simulate the Great Wall under body conditions it was near perfect.
Sleeping Bag inside Bivvy
The *Sleeping Gear*
MSR Bivy (basically a full sleeping bag cover: 200g US$66)
Nemo Strato Down Sleeping Bag (rated to -4C in normal use, 1,650g ca. US$230)
NeoAir XTherm (extreme 4 season mattress, rating R-5.7, 570g US$185)
Reflective Ground Pad from Decathlon (Forclaz 100, 210g, cost US$6)
Bag fleece Liner (Decathlon, ca. 850g and US$10)
Sol Emergency Bivvy Sack (130g ca. US$20)
The *Clothing*
Light beanie (dispensed with a liner, too hot)
Soft fleece neck warmer (dispensed with, too hot)
Arctic rated woollen socks (dispensed with, too hot)
Winter merino wool hiking socks (I could even have gone bare footed since my feet were still very warm)
Minus 33 light thermal Long Johns (I was nice and warm down there)
Up top I had left off any thermals and just had on a Quechua synthetic long sleeve, high neck, polo and a light Mountain Hardwear fleece - again more than warm enough but not enough to make me sweat (a good decision to leave out the thermals)
Sleeping Bag & Space Blanket inside Bivy
So how did this all work out ?
*Ground* : the 2 pads worked perfectly in sync, nice and cosy underneath and comfy too.
*Air* : very toasty inside the sleeping bag with the Sol bivvy, liner and fleece. Too toasty in fact (see above for items dispensed with).
*Sleep* : Good and undisturbed in any way by a need to regulate temperature, after the first 30 mins when I was too hot and needed to dispense with beanie liner and the arctic wooden socks.
*Condensation* : not an issue inside the bag as I wasn’t sweating, a little around the mouth/face ‘breathing hole’ but not enough to disturb me or need serious drying out in the morning. The MSR bivy completely covers you but there remains an overlapping gap (conveniently this is similar to the Nemo Strato which also completely covers you when tucking your head into the top section) which I assume is to allow some condensation to escape whilst not letting in too much cold air.
Conclusion :
I reckon this could easily be a good setup down to at least -10C maybe comfortably as low as -15C. With my much heavier Arctic-rated Minus 33 merino wool long johns and top, plus the Arctic socks and beanie liner then maybe even -20C wouldn’t be an issue either.
Perfect therefore for my upcoming Great Wall 8 day / 6 night (camping) hike since current low temperatures at night will not be colder than -17C maybe on a really cold night as low as -19C.
Even better, the next morning a nice hot coffee and hot breakfast was only as far away as my kitchen !