Metal ceiling decking condensating

Guest User
7/22/2013
Hello, We have a roof that was installed over top of on exsiting roof of our 40000 sq ft commercial building. What we have now, is a pvc material made by DuroLast over top of the original gravel and insulation and tar. We cool and heat our building with forced air and these units sit on the roof. We have been experiencing what we thought was a roof leak or AC leak, but disovered that our roof/ceiling is condensating do to the cold air seeping through the ceiling. What the roofers are saying, is that we have too much positvie pressure inside, causing cold air to escape anywhere it can, even through the ceiling decking. This only happens on very hot days, which we have had here in Ohio for the last month, no problem in the Winter. The roof is white and the surface temp doesnt get above 80 or so and the PVC material will not condensate, this was proven from test done at the factory. The way to stop the leaks is to equalize or adjust the building pressure, so they say. Does this make sense to you? Can you give me any advice? Thanks
Eric Novotny
An informed customer is the Best Customer!
7/24/2013
Larry, If you have enough cold meeting warmer surfaces, you are going to get condensation. The AC unit should be removing most of the moisture from the air inside the conditioned spaces so it sound like you have some air leaks that are allowing the more moisture laden air (summer time air that is high in humidity) into the space to condense and collect on the colder surfaces. The cold air does not that the moisture content that is condensing and it certainly would not condense on the warmer surface. You have either a roof leak or some warm air from outside mixing up against a cold interior surface. How was the new membrane put down?
Guest User
9/3/2013
Eric, Thank for replying back to me. I have tried many different things to try and stop the dripping/condesation, but havent had any success. I came in on a Sunday, to measure the ambient inside air temp and ceiling temp. The data that I recorded was, outside air temp was 88, inside temp 80, ceiling temp was 82. The unoccupied setting for the AC, weekends and weeknights, are set at 85. this past weekend, i left all units run at a temp of 75 and we had a very hot weekend, close to the 90's, this morning i have a lot of dripping off ceiling. I only get drips, in one main area of ceiling, which happens to be on the downward slope of the ceiling, but the flutes of the ceiling decking, runs across the slope and not with the slope, so any water on top of ceiling, will run across the slope and not down slope, since it seems to follow the flute of the ceiling. Why doesnt it condensate all over the plant, instead of just one main area? Is there an expert in this field that can come and look over our situation? I would have to say that we have had this problem before the new roof was installed, we just blamed it on the roof, but now it seems to be something else. The membrane of the pvc roof, is screwed down, through the old roof into ceiling decking and welded at each overlap and joint. Thanks,
Eric Novotny
An informed customer is the Best Customer!
9/3/2013
Condensation is a tricky beast to track down from time to time. Your best bet is going to get someone in there with an IR camera and have a thorough leak investigation done. The IR camera will help our quite a bit.

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