Waterproof, Windproof, & Warm!!! The SOL Thermal Bivvy reflects up to 80% of radiated body heat to help keep you warm and dry in emergency survival situations. Whether the power goes out in your home in cold weather, your car is stranded in a snowstorm, or your day hike has turned into an overnight survival situation, the SOL Thermal Bivvy will help keep you warm and protected from the elements. The non woven fabric is both wind and water proof. This year round bivvy is also ideal as a light weight replacement for your sleeping bag when temperatures are above 50F/9C.