The more colder the weather the more important it is to choose the right bivvy.#break#Choose bivvies that dont have problems with condensation.#break#Of course you can just use a plastic bag as a bivvy sack but it wont be much of a protection though it would be really light.#break#The main function of a bivvy is to keep the users sleeping bag dry and to increase the warming capacity by at least 10 degrees.#break#Bivvies are for people who travel solo in the backcountry, are on hiking trips that take longer than a day to complete, camp during long-distance biking trips, want to shed as much weight as possible and dont mind sleeping in limited spaces.#break#Theyre perfect for summer ultralight backpacking.#break#Perfect timing, Ive just decided to be an ultralight so I will be using a bivvy instead of a tent.