This weekend my rescue group did some field training, while mostly land navigation and trekking we had them spend the night living out of their “24 Hour Packs”. A “24 Hour Pack” is a basic, lightweight kit that would allow the owner to live in the field and carry out their mission for 24 hours. I took this opportunity to test some of my survival gear; specifically I wanted to test out my shelter setup.

In my “24 Hour Pack”, I carry a pretty simple shelter set up, 1-Adventure Medical Themo-lite Bivy, 1-Supersized garbage bag and 1-lightweight backpacking poncho. I made a simple lean-to out of the poncho, my trekking poles, 4 zip-ties and a few feet of 550 cord. But I was more interested in how the Thermo-Lite Bivy would do.

I was dressed in an Underarmor LooseGear long sleeve shirt and ColdGear 1/4 zip top, Patagonia Capilene SW Bottoms, 5.11’s TDU (Poly/Cotton) and Smartwool hiking socks. I also had a Mountain Hardware Micro Dome beanie cap and Underarmor ColdGear liner gloves.

When I went to bed (2200) it was about 40deg F, I initially was in just the Thermo-lite bivy and was as warm as I could have wanted to be. Over the next two hours I slept comfortably, but was awoken by a strong draft at approx. 0000. When I awoke I checked my thermometer and it was now 34deg F, I pulled the plastic bag over the bivy and went back to bed. I slept intermittently over the next 4 hours or so. I was still warm enough to sleep, but could feel the cold. At approx. 0400 I checked my thermometer and it was 28 deg F. Now my feet were noticeably cold and my upper body was chilled, but still comfortable. At 0730 when the sun came up, I was chilled and ready to get up and out of my bivy.

I have used a Thermo-Lite bivy before in various situations and it had always exceeded my expectations, but this was the first real test as a survival tool and it did do better than I expected. It is light years ahead of a basic disposable space blanket or a heavier duty space blanket, as my partner found out… My conclusion, this setup will work for me in 90% of the environment I will find myself in. In colder conditions, this setup would still work because those environments would provide more resources to maintain warmth and I would already have better clothing. For our drill, although it was done to 28deg F at night, it was in the high 70s during the day. Because of this, and of my desire to just carry what I would if I only planned on being out for the day, I had less clothing than I would if I had planned on operating at night.