Originally Posted by
g33k
Should I use a windbreaker over multiple other layers, or go with a heavier jacket?
Layers, always layers.
This allows flexibility as you warm up from exertion. Removing a layer lets you balance cooling and heat retention across the whole body.
With a single heavy jacket, all you can do is unzip the front, so you get a cold chest and a sweaty back. Not good.
I use a windbreaker over layers all the way down to 4°F. Hasn't gotten colder than that in the past two winters, so I don't know how much colder I can go with the combo.
Edit: Look at my avatar. That photo was taken last February, and the temp was around 25°F as I recall. I rode about 35 miles that day. I'm wearing a baselayer, long-sleeve wicking t-shirt and my BikeForums.net Great Lakes Region short-sleeve jersey. The three layers on my torso keep me warm. The two layers on my arms allow for some cooling so I don't overheat.
Commuting, a short-sleeve t-shirt, business shirt, and windbreaker would give the same coverage, and in fact, that's what I wear on top in winter commuting.