When designing your sleep system, your first concern is conduction.
If your 98.6-degree body is on an 80-degree ground, conduction will occur the entire time you’re in contact with the ground.
You must first insulate yourself from the ground using something like a Therm-a-Rest.
After that, you need a good sleeping bag system, such as Snugpaks.
This is the Snugpak Special Forces 1. It’s a lighter bag meant for slightly better weather:
If it’s colder, carry the Special Forces 2:
Your comfort level in the Special Forces 1 bag is 41 degrees Fahrenheit, and the lowest that you should be able to use it in is 32 degrees Fahrenheit. So basically, if it’s above freezing, use the Special Forces 1.
The Special Forces 2 has a comfort level of 18 degrees Fahrenheit, with a low at 10 degrees Fahrenheit. If it’s going to be below freezing, take the Special Forces 2.
Aim to take the smallest bag possible.
A center baffle allows you to zip those two together and use the bags in conjunction with each other, which is even better. So if it gets below 10 degrees Fahrenheit, you can zip both together and use them and still be comfortable.
In most cases, having a poncho or some sort of overhead cover is going to be enough, but then most military sleeping bag systems also come with a bivy sack. There is a Gore-Tex bivy sack, which is waterproof and windproof, basically a sleeping bag cover that allows you to use it as a standalone shelter. These are somewhat bulky, so carry the Snugpak bivy sack that’s designed to go with the Special Forces sleep system. Since this is a layering system, keep this sack inside your backpack and take it out if you go somewhere away from your main source of gear:
Then, last but not least, the Cocoon Mummy liner
Basically this is a CoolMax liner. It’s a thin, wicking layer, almost like a T-shirt material, but it’s basically a Mummy liner that sits inside your sleeping bag. It will give you an extra five to ten degrees of warmth, and really help with the wicking of sweat. The CoolMax liner is small enough to pack to go anywhere. If you don’t have your main sleeping bag, you can still use this wicking layer to pull some of the sweat away from your body (thermal blankets don’t breathe at all).
You can use the Mummy liners in conjunction with your sleeping bags (any sleeping bag system), depending on your environment.
That’s the sleeping system. Basically, you’ve got the following:
- Some sort of ground cover, ground insulation that protects you from conduction
- Your insulating material layer (actual sleeping bag). Options:
- Special Forces 1, patrol bag
- Special Forces 2, a heavier winter bag
- use those two in conjunction
- A windproof, waterproof layer, such as the Gore-Tex bivy cover, which will protect you from convection (the wind current that’s traveling across your body and taking your body heat with it)
- The Cocoon Mummy Liner (CoolMax Liner)