Most people in the PNW figure they need more glazing than is required in sunny but cold places. The clouds tend to bounce the light around. Have you read the info on permies about the Chinese Greenhouse?
https://permies.com/wiki/143395/Chinese-Greenhouse-Dan-Chiras#1122372
It's not exactly Wofati, but it is earth bermed and gives some good ideas about having internal thermal mass to help with temperature swings and decrease the risk of freezing.
I'm further north than you, and even with following some of the ideas in that book, I doubt I could effectively grow greens without some supplemental light to extend the day length and compensate for the weeks of cloud we typically get. If I grew the plants late summer and was just trying to "hold" them until I wanted to eat them, I'd have more luck, but that means that I can't be growing my tomatoes in the same space when I need them to be ripening. People talk a lot about "winter gardening" in my region, but I've got a shady property and I've had minimal luck with the concept - the plants grow too slowly compared to slugs, bugs, chickens and people who want to eat them! A greenhouse would help with some of the issues, but even one of our fairly big greenhouse farmers, shuts down from the solstice to mid-Feb.
Aside: Have you considered sprouts? Fresh greens that rely on the stores of the seed, rather than the sun.