The last 2 winters I've worn a wickaway t-shirt under a thin liner shirt, either microfleece (when it is +-5 C) or wool sweater then a MEC SuperMicroft jacket. If it's really cold I wear a heaver rollneck wool sweater. I found heavier jackets too bulky to commute in during the winter and when it warms up on the commute I can take advantage of the pitzips on the jacket.