I’m not Cerebrus, but maybe I can help. :mrgreen:
First of all, one-way vents are fairly ineffective, though I don’t know that I would limit their effective range as only being 1 square foot. However, if you asked me if I would put them on the hospital roof in question and believe they would solve the problem? My answer is indubitably, NO!
Before I get further into my answer, I would like to know how old the roof is and if you had anything to do with the installation? If so, was the insulation board stored on the roof only in the factory shrink wrap, or was it properly tarped and elevated above the ground? Did any of the insulation get laid out and rained upon before the new roofing was installed?
The reason I ask, is they obviously have a vapor-drive issue with that roof. The moisture typically will be driven into the roof board insulation during the night, but will condensate on the bottom of the membrane during the day depending on interior and exterior temperatures and humidity. If the building is fairly new, the excess moisture may eventually dissipate and roofing components moisture content will near equilibrium.
You say the hospital keeps the humidity at 50%, but I don’t know if that is high for your area. If it is high, then a vapor-barrier should have been installed with the roofing. Chances are, this is not the case unless the hospital has some walk-in coolers or something like that beneath the roof that is experiencing moisture problems.
Also, are we talking about a metal roof deck, concrete or did they install insulation over lightweight concrete?
Too many questions for me to give you a good answer right now. Give me some more background information and I may be able to help you better.
Opps, just went back and saw where you said the roof is 6 years old. So, it sounds like there are some other issues. Once again, what kind of roof deck do you have? Are there any roof leaks that you know of, or were there any? That moisture is entering the system some how.
Did the roofing consultant take cores and have gravimetric testing performed, or how did they determine there was an elevated moisture content?
Are you sure the fasteners failed due to corrosion, or could it have been a failure related to wind uplift?
Let me know some more, and maybe I can help.
When all is said and done though, I’m going to put my money on them having a problem with the dew-point falling within the top layer of insulation. If I’m right, and the project was a re-roof of an existing building, then the problem may have been caused by an increase in the roof insulation value. Sometimes just adding more and more insulation to a roof is not a good thing.