how warm is this jacket? with a shell can...
how warm is this jacket? with a shell can you wear this, a tee, and a shell in 0 degrees?
Probably not. It's about the same warmth as a mid-weight fleece. If you are walking around in 0 degree weather (assume you mean Fahrenheit), this will not be warm enough. In my experience, I can wear this jacket into the 30's (when I am standing still) or into the single digits (when I am working out vigorously).
Look at the ATOM SV jacket- it is much warmer. It uses a heavier weight primaloft insulation (100 grams compared to 70 grams) and does not have the size fleece panels. it will suit your needs. If you want something warmer still, you can move up to the Kappa series of jackets which use 133gms on the AR and 200 on the SV versions).