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.

 

[phamENG]

That's my bet from here. Don't see any salt buildup, so it's unlikely to be water migrating through the block. It's very localized, so probably not runoff from anywhere else. Could be rainwater being blown into that unit and running back out, but either way it looks like some small but not insignificant amount of water running out and down the block there.

 

[milkshakelake]

Condensation occurs at large temperature differentials where there is little to no insulation. So for example, this would be an exposed (uninsulated) cold water pipe in a hot room, or vice versa. So maybe check that the vent and any ductwork around it is properly insulated. To investigate this, you'd try to look for water running down when the system is in use. Meaning it has to be really cold or hot, and the system is working like crazy.

Second, maybe the vent itself isn't properly waterproofed and water is coming from rain. I would ask them to take a photo of that area, above and below, when it's raining hard. Kind of like today, where I am. See if you can spot any leakage.