Polartec as a base/insulating layers all over the body, anything {wind,water}proof or +1 layer on top of them if i'm planning to go slow (like, <130bpm), otherwise nothing or a decent (>15l/m²/day) steam-permeable waterproof membrane if the rain or powerful wind is probably an issue. Does the job better than wool as it doesn't get wet. Balaklava on my head. // Russia/St. Petersburg here.