Sealing Styrofoam Insulation

[Starchy]

Further to my previous post and all of the excellent responses to that post I made re. condensation on my insulated basement walls, (Condensation on basement insulation) where my problem was a double vapour barrier in my basement, I have a new question. In another room in my basement, I have removed all of the 6 mil poly, fiberglass batts, and 2x4 studs, leaving the rigid foam panels on the walls and ceiling. (The ceiling of this room is a 4" thick concrete slab that is in fact my veranda floor.) The problem was the same as the other room I did, however it had a severe moldy smell. Removing the moldy 2x4's and washing all of the rigid foam has corrected the smell. I am about to add spray foam to the top of the foam boards and tape seal all of the joints of the foam panels. My question is: do I spray foam the joint of the foam panels where they meet the floor, thereby sealing the top and bottom bottom? I kind of think I should, to completely seal any warm moist air from getting behind the rigid foam panels, but want to confirm my thoughts before I do something that cannot be undone.
Thanks for any input. Need to get this room done as it is 40 below zero today where I live. Brrrr.