You can wash ANYTHING that is not dryclean only in cold water. Many people only wash their clothes in cold, to avoid having to separate their clothes out, or accidental shrinkage.
Yes, heat causes shrinkage (when I'm losing weight, I don't go out and buy new clothes, I just progressively shrink them with me by using increasingly hot water and increasingly higher settings on the dryer... I can get 2 sizes of shrink out of most clothes that way).
Cold water does not work as well as warm/hot, but it does still work. Wash Warm/Rinse Cold (as opposed to ww/rw), will shrink less than W/W, but will still cause SOME shrinkage.
I use hot water on fabric that needs to break up oils/it doesn't really matter that much if they shrink. So, HOT/Cold for sheets, towels, & socks... Cold/Cold for everything else.
I also set the dryer on LOW for absolutely everything EXCEPT sheets/towels/socks... which all get dried on HIGH.