Another important part is adequate calories and a hot tea or vegetable broth does wonders. Keeps your body core warm and is a huge psychologic boost. The canadian is correct that you may need up to 6000 kcal per day. Having spent a lot of time in the military under adverse conditions, I never understood why they lowered the MRE calories so much. In wet/cold weather with wet snow and doing all required tactical tasks, one will easily burn 4500 kcal a day. That assumes that you work and not just hang out to conserve energy. Cheapest emergency food is ramen noodles, some chocolate and multi-vitamin tablets. Easy to store. Comparably light weight, but a little more bulky than real emergency rations.