Are you talking medicinal or culinary herbs? It all depends on what you want to grow...

Unless it is warm and sunny in the NW during the winter, you will need an indoor light growing set up for winter herbs. You could rig lights and heat in the greenhouse, but it would be less expensive to set up grow lights in in the basement.

The herbs need the equivalent of full sun at summer intensity and at least 70F temperatures. With an indoor setup, the flourescent lights need to be on for 14 to 16 hours a day.

There is a gardening under lights forum, try posting your question there.