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Discussion Starter #1
Hey all,

I have a thread that started in the roofing forum here :https://www.diychatroom.com/f9/8-year-old-leak-making-unsolved-mysteries-695439/

Basically I have been getting a leak coming from the ceiling for atleast 8 years now and I just discovered it a couple of weeks ago. Now after some extensive troubleshooting, I am pretty confidant that the leak is not coming from my roof anymore and instead it might be coming from the HVAC system.

I have a few layers of roofing material stacked ontop of each other and when I cut the various layers apart, I saw the dripping come from between the top roofing layer and one of the bottom ones. I am having trouble locating the source of where the water is coming from.

Since we have had no rain in the past week or so, and it still "drips" consistently, I have ruled out a roof leak from being the issue. THat said, my AC is on the roof (suspended on girders and the condensation water is flowing into my gutter), and there are several locations that the ductwork penetrates into my roof.

I specifically looked into the supply duct last night and I took my thermal gun out to the rooftop, where my AC unit is located, and started inspecting the ductwork, and one glaring item that popped up was that on the main supply duct that goes directly into the roof, there is a section right above it that showed a large temp variation vs. the other parts of ductwork. I was measuring 63-66F surface temps (83F ambient, 57% humidity), whereas the other parts of the supply duct coming from the AC was ~78F. I decided to look closer, and lo and behold, there was a good amount of condensation on the surface of that duct in that low temp location (attached pictures). So a few comments / questions here.

1. Assuming that there is condensation on the outside, can I also assume that there is condensation on the inside? If that is the case, then I can see it causing some leaks.
2. During the day when its super hot outside, that is when I see the "dripping" from my ceiling. Does the hotter outside temp cause more condensation to form?
3. If I insulate this problem area from the outside, and assuming that it is condensating on the inside, do you think that will mitigate this issue? And how would I go about insulating the ductwork from the outside? is there some type of "tape" I can use? or what is recommended?

since last night, I have insulated the problem area outside, but not sure that will make any difference. I will track it as in this temp it usualyl starts leaking by noontime.

Here are some pictures. any help would be appreciated!
 

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Discussion Starter #2
just checking in to see if anyone has suggestions on what I can try next. Currently im dehumidifying the room incase it's just residual water inbetween the roof layers. I havent seen anything drip down recently, but could it be possible that the de-humidification process is drying up the "drips" before they can fall down? hmmm.
 

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I did not totally follow the line of question (especially when discussing inside/outside as it relates to the inside/outside surface of a duct and the inside/outside living space of your home which the duct may be traveling through) nor did I completely read the other tread. That said, if I saw condensation on the outside of a supply vent I would not be concerned about condensation on the inside of this same vent. Since the outside surface condensation indicates that the duct is cooling the outside unconditioned air, causing it to lower and reach the dew point. Which in turns means that the temperature inside the supply duct is rising, which would lower its relative humidity and thus not lead to any internal condensation.

This is all related to warmer air's ability to hold more moisture. As you purpose, insulating the duct will help slow the drips, as well as anything you can do to lower the humidity of the surrounding air through which the air ducts travel.
 

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Discussion Starter #4
I did not totally follow the line of question (especially when discussing inside/outside as it relates to the inside/outside surface of a duct and the inside/outside living space of your home which the duct may be traveling through) nor did I completely read the other tread. That said, if I saw condensation on the outside of a supply vent I would not be concerned about condensation on the inside of this same vent. Since the outside surface condensation indicates that the duct is cooling the outside unconditioned air, causing it to lower and reach the dew point. Which in turns means that the temperature inside the supply duct is rising, which would lower its relative humidity and thus not lead to any internal condensation.

This is all related to warmer air's ability to hold more moisture. As you purpose, insulating the duct will help slow the drips, as well as anything you can do to lower the humidity of the surrounding air through which the air ducts travel.
Thank for the response. So in regards the HVAC condensation being the culprit, the area that I saw outside that was "less" insulated is most likely not condensation on the inside. Your reasoning makes sense.

This leak is just so tough to troubleshoot at this point without ripping out every layer until the 2nd roof (there are 3 layered ontop of each other) And in order to get to the 2nd layer of roof from the inside, I have to break through sheetrock, then through the first layer of decking, and then to roof #1, and then there's roof#2 that I see the water gliding off from.

The supply duct penetrates through all of those layers, so is it possible that over the years that condensation formed from the supply duct(s) and just got trapped in between those roofing layers?

And is there a way that you guys recommend that I troubleshoot this without ripping the entire roof apart (either above or below)?

FYI, I have a humidifier running 24/7 now bringing the room's RH down to 40% (home is ~55%). Hopefully that will draw more water out from between the roofing layers.

Or could I be missing something else that can help me pinpoint this leak? thanks everyone!
 

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So prior to using the dehumidifier I would often see multiple drips coming from the holes I cut in the in the ceiling but now it appears to only be coming from the hole I cut in the highest hole. That leads me to believe that the source of water is from further up in the roof and it’s traveling down to all the other “holes”. That said I’m thinking it might still be that the roof was just saturated with water from previous leaks and that it had nowhere to go BUT up and now it’s finally got a chance to release after I cut all the holes. Here’s a picture showing how the ceiling it looks now after I cut various holes from the lowest pitched point (on the right side)and going steadily higher(to the left side). What do you think of my hypothesis?
 

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I would be happy to hire an “expert” to investigate. But I’m not sure what they would tell me other than I have to cut everything up. I supposed I can cut a little more of the ceiling/Sheetrock To try and locate the source before I give up and Just rip everything out from the top.
I logically I just can’t see the leak coming from the “top” of the house anymore. It has to be something from underneath. I just don’t know what.


 

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I would be happy to hire an “expert” to investigate. But I’m not sure what they would tell me other than I have to cut everything up. I supposed I can cut a little more of the ceiling/Sheetrock To try and locate the source before I give up and Just rip everything out from the top.
I logically I just can’t see the leak coming from the “top” of the house anymore. It has to be something from underneath. I just don’t know what.
I think you may have to attack the ceiling around where the duct comes thru the roof.
 

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I think you may have to attack the ceiling around where the duct comes thru the roof.
Yea, I might have to do that. One thing I did notice was that the screws that penetrated through the decking in the proximity of the main supply duct were not rusted like the ones in the areas with the clear water damage. All the screws around that area were rusted, which indicate to me that there was water going through there, or water that was ponding there. That said, if water just "passes" by the screw, maybe that is not enough to make the screw rusty? So in that case I might still need to open that area up. :(
 

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I also think you should closely inspect around the supply vent as it penetrates the exterior roof. Potentially tear it out, or tear out underneath (from the inside of your home) until you can 100% confirm there is no source of water entering there from above. As it seems plausible that condensation on the outer duct surface that is occurring when the duct is still outside on your roof could be trickling down into the interior. In the in-between zone where the supply duct penetrates the roof I would think it could be insulated or otherwise filled in so that there is little to no air there to allow condensation to form regardless of the home's interior humidity.

I saw the wide field of view photo of your roof in post #48 of the other thread. I know commercial buildings often have HVAC equipment on the roof, but I was surprised to see all the duct work sitting out in the open. Seems like it would make your system quite inefficient. e.g. on hot days the inside return air would be further heated before entering the evaporator to cool down, reducing the amount of cooling and then partially heated again in the rooftop supply duct before it can re-enter the home. I would think your home is a great candidate for a mini-split system when it comes time to replace.
 

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Discussion Starter #11
I also think you should closely inspect around the supply vent as it penetrates the exterior roof. Potentially tear it out, or tear out underneath (from the inside of your home) until you can 100% confirm there is no source of water entering there from above. As it seems plausible that condensation on the outer duct surface that is occurring when the duct is still outside on your roof could be trickling down into the interior. In the in-between zone where the supply duct penetrates the roof I would think it could be insulated or otherwise filled in so that there is little to no air there to allow condensation to form regardless of the home's interior humidity.

I saw the wide field of view photo of your roof in post #48 of the other thread. I know commercial buildings often have HVAC equipment on the roof, but I was surprised to see all the duct work sitting out in the open. Seems like it would make your system quite inefficient. e.g. on hot days the inside return air would be further heated before entering the evaporator to cool down, reducing the amount of cooling and then partially heated again in the rooftop supply duct before it can re-enter the home. I would think your home is a great candidate for a mini-split system when it comes time to replace.
Thanks for the reply RNS! I agree with your assessment that there probably needs to be some more uncovering of the wood around the duct area. if you saw on my previous post, I did wrap the area that was pretty clearly leaking heat (insufficiently insulated) on the outside. also from the outside, there is a clear layer of roofing membernge that overlaps the ductwork so there should be no leaking from "external" condensation. this might not have been the case 2 years ago prior to my most recent roof layer, which is why I keep going back to, "is this old water that just needs a place to escape now that I have the ceiling open"

As for your comment of the HVAC ductwork being "outside" of the house, that's because the previous owners were trying to preserve as much internal real estate as possible, and I don't have much ceiling space to run the central air ducts. These are old attached homes built in 1920s.
However, the ductwork is internally insulated, and I have used my thermal gun to check on heat loss, and for the most part they are doing an ok job (5-10 deg below ambient surface temps at night, with AC running). The biggest heat leak that I saw externally has been fixed by the duct wrap and some weatherproofing.

I agree with the mini split and I looked into the costs and they were quite astronomical to have to rip down all my walls, run extra plumbing to all my rooms, run new circuits, and I would need the special units with more heat since I don't have baseboard heat and everything runs through my ducts for heating/cooling. I don't think that is feasible especially since the existing ductwork is run for the entire house, and the rooms feel fairly comfortable. However, I might be ok with getting some supplement ductless units for more cooling.

With all that being said, when it gets colder outside, I might run into the same issue with "leaking" if my internal warm air hits the cold duct/interior roof layer right? I'm just trying to quantify how much actual condensation is needed to cause the damage I see right now. I don't think that its possible, which again brings me back to was this damage from an actual roof leak before and the little drips from when I run the AC on the hot days is just a coincidence and somehow residual water from the years of other leaking.

Finally, should I keep running the dehumidifier in the room right now? My thinking was that if it is old water that needs to dry off in between the roofs, this Dehumidification process will help. However, if it's the small dripping from the AC, or something else, then this dehumidification might "mask" the issue, making it harder for me to find the small leak.

I wish this was easier to troubleshoot, but I can't think of anything else at this point. thanks all!
 

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Discussion Starter #12
So I see a few spots dripping today (about 1 drop every 1-2 min) and I decided to stick my snake cam up through the ceiling, starting from where the drip was coming down, and followed a small stream until I found a pretty wet area, where I am assuming is the source of the "stream". That said, I can't tell if the pool of water is growing (still an active leak), or if the pool of water is just residual from the past few years of a roof leak.
The strange thing is that the leak only comes on when it's hotter out and the AC is on. Does this mean that it's definitely AC related? Or could there be another reason?
I haven't tested out whether the water still flows when it's HOT and NO AC (it's too uncomfortable). but think that's worth a shot?
Is there some property of water and roof that when it's hotter out and there's cool air in the room (AC) that there is more water flow?
 

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So I see a few spots dripping today (about 1 drop every 1-2 min) and I decided to stick my snake cam up through the ceiling, starting from where the drip was coming down, and followed a small stream until I found a pretty wet area, where I am assuming is the source of the "stream". That said, I can't tell if the pool of water is growing (still an active leak), or if the pool of water is just residual from the past few years of a roof leak.
The strange thing is that the leak only comes on when it's hotter out and the AC is on. Does this mean that it's definitely AC related? Or could there be another reason?
I haven't tested out whether the water still flows when it's HOT and NO AC (it's too uncomfortable). but think that's worth a shot?
Is there some property of water and roof that when it's hotter out and there's cool air in the room (AC) that there is more water flow?
In a perfect world you would have venting above the insulation. '
If there is a lack of insulation around the cold duct, the moisture in the warm air would be attracted to the cold duct. That doesn't explain water above the membrane and under the new roof. Or is it below the old roofing?
 

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Discussion Starter #15
In a perfect world you would have venting above the insulation. '
If there is a lack of insulation around the cold duct, the moisture in the warm air would be attracted to the cold duct. That doesn't explain water above the membrane and under the new roof. Or is it below the old roofing?
So I used a thermal gun to the cold duct, and I did see a temp variation near the ceiling, but when I touched it, there was little to no condensation. That said, this was in the inner most layer (surface) from the INSIDE, and I have already determined that the water is flowing from above the "2nd roof and below the plywood of the 3rd roof". Therefore it still might be possible for the hot moist air trapped between the two roofs to hit the duct cause condensation and then the water forms.

I don't know of a good way to vent the ceiling. I certainly do not want to add additional penetration points on the roof. Is it possible to PULL the warm air from the ceiling area into my master bedroom? or pull it to some other place?

-T
 

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So I used a thermal gun to the cold duct, and I did see a temp variation near the ceiling, but when I touched it, there was little to no condensation. That said, this was in the inner most layer (surface) from the INSIDE, and I have already determined that the water is flowing from above the "2nd roof and below the plywood of the 3rd roof". Therefore it still might be possible for the hot moist air trapped between the two roofs to hit the duct cause condensation and then the water forms.

I don't know of a good way to vent the ceiling. I certainly do not want to add additional penetration points on the roof. Is it possible to PULL the warm air from the ceiling area into my master bedroom? or pull it to some other place?

-T
No ,usually the venting is above the insulation and would enter and exit under the soffet area at each end of the joists.
When you tore this down was the insulation right against the roof or was there a gap like 1 1/2" between the insulation and plywood?
 

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Here's a video from the endoscope. Does this look like "active" water to you guys, or is this more like residual water from an old leak?

https://flic.kr/p/2jrZyyo

Yes, that looks like some active/fresh flow to me. But it also looks like it has been happening for quite a while.

What was that white pipe that comes into view around the 50 second mark? Could that be the source of the leak?
 

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So I see a few spots dripping today (about 1 drop every 1-2 min) and I decided to stick my snake cam up through the ceiling, starting from where the drip was coming down, and followed a small stream until I found a pretty wet area, where I am assuming is the source of the "stream". That said, I can't tell if the pool of water is growing (still an active leak), or if the pool of water is just residual from the past few years of a roof leak.
The strange thing is that the leak only comes on when it's hotter out and the AC is on. Does this mean that it's definitely AC related? Or could there be another reason?
I haven't tested out whether the water still flows when it's HOT and NO AC (it's too uncomfortable). but think that's worth a shot?
Is there some property of water and roof that when it's hotter out and there's cool air in the room (AC) that there is more water flow?
I am sure you know this, but I would assume that the source of water is where ever is the highest point of wetness. Water is tricky in that surface adhesion can cause a small trickle to flow horizontally for quite some distance, and capillary action can draw it up and in almost any direction. But gravity usually wins and it will flow downhill if it does not evaporate first.

I don't know where you live (the summer time weather in your area) but the summer heating means the air outside holds a lot more moisture than during other parts of the year. And given the age of your home it is probably leaking enough that this warmer/moister air is continuously creeping back into your living space, causing the home to remain relatively humid. I certainly experience this at my home, and it has been very humid over the past few weeks.

From what you are saying it does seem like you have determined the approximate cause, now you just need to better pinpoint the source. If you suspect it is just condensation that is forming inside the home (not entering from the outside) I would try to move the indoor humidifier or get enough indoor de-humidification capacity to really drive down the indoor humidity until it is closer to the "dryer" side to verify if that was really what was happening. Keep in mind that the hottest and moistest air in your home is at the highest point, since hot + moist air is lighter than cooler air. So if you think your indoor relative humidity is X at floor level it will be higher where this roof duct enters the home.
 

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One other idea for monitoring the indoor humidity at the roof vent. Get the "Govee Thermometer Hygrometer, Accurate Indoor Temperature Humidity Sensor..." and place it as close to the duct entry point as possible. I got the $12.99 version with bluetooth from the big online store and it is responsive. It could help you troubleshoot in that once you have it paired with your phone you do not need to physically touch it, you can periodically connect and download the data. The smartphone app will graph temperature and humidity levels so you can get more insights into what is going on.
 

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Hey Neal,

There is virtually no space between the insulation and roof decking. There are a few “compressed” insulation sheets that have a channel on the top where there is maybe a 2 inch gap of space. But the majority is butter against the top.

So I used a thermal gun to the cold duct, and I did see a temp variation near the ceiling, but when I touched it, there was little to no condensation. That said, this was in the inner most layer (surface) from the INSIDE, and I have already determined that the water is flowing from above the "2nd roof and below the plywood of the 3rd roof". Therefore it still might be possible for the hot moist air trapped between the two roofs to hit the duct cause condensation and then the water forms.

I don't know of a good way to vent the ceiling. I certainly do not want to add additional penetration points on the roof. Is it possible to PULL the warm air from the ceiling area into my master bedroom? or pull it to some other place?

-T
No ,usually the venting is above the insulation and would enter and exit under the soffet area at each end of the joists.
When you tore this down was the insulation right against the roof or was there a gap like 1 1/2" between the insulation and plywood?
 
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