It was 20F today and my layers were all cotton (outside of my outer windstopping layer). You can always try a shorter ride tonight to see how it feels and adjust accordingly.

In the upper teens and low 20's I wear jeans and t-shirt with a track jacket or other lightish middle layer with a ShowersPass Rain/Windproof jacket on top - single digits I'll put on an under armor type layer. On my legs I do wear tights under jeans or slacks when it's in the teens, and I wear a beanie under my helmet for anything below 32F and cover my face when it is in the teens as well. I have some windproof mittens that I wear for the 20's and under.

What works for me may not work for you, though. How far is your commute?