Vertical Streaks on CMU inside face

[PSUengineer1]

In the attached photos is the north elevation of a 2-story school addition. CMU exterior walls. Steel floor/roof framing. Vertical stains are below a second-story joist bearing at north exterior wall (see dashed outline in Photograph 1). No streaks are below any of the roof framing members above this. My theory is that this staining is either from condensation on the bar joist and/or water leaking from the unit ventilator in the second-story classroom above. My question is: what do you think the vertical streak staining is from? Thanks.

 

[phamENG]

Is that grate for some sort of AC unit in that room? That would be my first guess.

 

[PSUengineer1]

Is that grate for some sort of AC unit in that room? That would be my first guess.

Yes. it is a unit ventilator on the second-story above. I think that is what it is from. You think just condensation from the unit (i'm not an HVAC guy)? Thanks.