Can lighting roof moisture problem
This winter I bought a 2 floor condo on the top floor of a 3 story brick building built in 2012 in Chicago, with hot humid summers and cold winters. During the hottest days, when it reaches 90+ degrees, I have found water around the recessed can lights on the top floor, which is directly up against the flat roof. I have also noticed a water stain on the drywall about 6 inches away from the ceiling, which I assume must be a wooden rafter.
The 2nd floor is actually a dryvit enclosed 600 sq foot “penthouse” on the 4th floor with its own flat roof. This roof has 2 vents on each end and the cans on each end do not show the same moisture problem. There is a return HVAC duct on one end of the penthouse, but the can lighting nearby is least affected by the problem. The roof is a single ply rolled product (I think modified bitumen but I am not sure—it is gray in color)
Also of note is the AC system is single stage single zone, so this 2nd floor room never gets below 78 degrees on these hot days, which makes it surprising that anything could condensate at all.
Here is what I have tried:
1) Had 2 professional roofers inspect the roof for leaks. None were found.
2) Pull the IC-AT rated can lights out from below. Remove the damp fiberglass insulation found inside, and replace with new insulation. Caulk seal between can and drywall, add LED retrofit kit which has less leaks than the previous LED bulbs.
3) Placed standing dehumidifier in the room, brought internal room humidity down to 45% (from 55%)
Any ideas on what the next step would be? I am considering the following:
1) Add additional roof vent in the middle. My thought for this is that if the ends of the roof seem to be OK, maybe this will help. However, I logically think this would just introduce more humid air to the roof space and make the problem worse.
2) Paint the roof with an elastomeric white roof coating such as https://www.homedepot.com/p/Henry-4-75-Gal-687-Enviro-White-Roof-Coating-HE687406/202091034. If this problem only happens on the hottest days, maybe the solution is to lower the temperature in the roof. This could have another benefit of cooling the room (which is of course always hot due to the single zone single stage AC over 2 floors..but that is a different issue entirely) I’m also not sure how much of a difference this would make anyway (if the claims are real).
3) Pull out all the can lights entirely and replace with fixtures, re-insulate (access is only from below). There are also overhead speakers built into the ceiling that I assume would need to be removed as well in this option.
4) Remove the vents, lay down rigid foam insulation on top, and put a new membrane on top. I think this is the nuclear option – just give up on the current roof and try again with an unvented one. I imagine this would be the most expensive route as well
Any other ideas that I am not thinking of? One thing I am surprised about is why the previous owners who lived here for 5 years claim they have never seen this before. While it is possible they are lying, I don’t see any signs of drywall repair on the ceiling.
Really appreciate the help, I am at a loss for what to do here.
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