If you know that you are going to be facing very cold temps; but working hard enough to sweat, then having to sit still, you might want to experiment with the "vapour barrier" theory of staying warm, rather than the "layer" theory.
In short, make your first layer impervious to moisture, then add conventional insulation.
When I first started, I used drycleaners bags, make a hole just big enough to stretch over your head, and holes just big enough for your arms. And the only thing under the bag is my briefs. Then a T-shirt, and a light sweater, a pair of mid-weight insulated drawers (long-john pants) followed by a pair of lined jeans, and you will amaze your friends and yourself at how warm you are, if you stay out of the wind. And if it's windy, you just need to add a wind/waterproof layer over top.
After a winter using the drycleanrs bags, I bought a lightweight wetsuit, 3mm neoprene, with short sleeves and short legs, like waterskiers use in cool temps.
For the last 7 winters I've worked in the Fort Saint John and Fort Nelson area of BC, so I'm passingly familiar with cool temps.
(find Juneau Alaska, then go east 400 miles)
"Those who have long enjoyed privileges as we enjoy, forget, in time, that men have died to win them."
Franklin D. Roosvelt