In preparation for an upcoming winter cross country ski trip, I put together a MYOG bottle boot to keep my extra water from freezing at night. Using a double layer of Reflectix, I was able to prevent warm tap water in a 1L Nalgene HDPE bottle from freezing during temperatures that ranged from 2 above zero (F) to -1 below for 10 hours.
I’ll have to work on its weight, but the bottle boot and cap (which fits inside the boot) weighs right at 3 ounces.
