Love fleece -- 1/2 zips, vests, jackets and blankets. Perfect for a SHTF bag. Quality matters, of course, as with most things.

Polartec 300 is quite toasty. 100 is good for a lighter layer.

For old times' sake, I just bought a boiled-wool 1/2 zip from LL Bean.

Do you have a good waterproof parka in your SHTF bag?

Some quality fleece and a waterproof parka would be an excellent combo.

I strongly recommend anyone look into the Marmot DriClime Windshirts. A friend got me onto them when she began a series of Himalayan treks -- several in her trekking group wore them and swore by them. The lining is a thin soft fleece and the shell is highly wind and rain resistant. No hood. They are quite light and pack down small.

They have vest and jacket versions and are often on sale at REI as they've been around for at least a decade. I have several (they're like M&Ms - lots of great colors) and have them spread around home, my camping trailer and in my car, at all times.

They can be used as a layer and as a stand-alone jacket. Great value even at full-price. But you can find them marked-down. They have men and women versions.

Marmot also sells DriClime pants.

http://www.rei.com/product/746706

http://www.rei.com/product/778914