"Take a look at Richard Nisley's article:
That article has got to be one of the greatest posts evah. It really laid out the basic scientific principles of matching clo to activity. After (re)reading it many times, it finally struck home that we are essentially only doing three things:
Each require their own clo configuration, ranging from least to most. Add in temp(s), rain, wind & dew point and the problem becomes one of mixing & matching for all possible combinations.
That's why you need limited clo while moving, but a lot of loft while sitting, and even more when sleeping. Hence, the classic (progressive) combo of capilene, polartec, windshirt, shell, vest/parka, bag/quilt and bivy/tarp/tent.