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Old 08-12-2020, 12:03 AM   #121
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


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Thanks!
Sorry I didn’t understand fully your comment. We’re you saying that you think that most of the damage could have been from condensation in that part? Or you meant that it is not likely that it’s just the condensation and it could be other factors (like roof leak)
The fact that I saw all that water flowing to the top from pushing on it made me think that over 8 years that this water issue can compound.
As for why the ceiling is still dripping, your explanation of “thermal expansion” makes a lot of sense too. When it’s hotter out the water will take up more volume and is probably being “expelled” from the plywood, which when I last measured was about 40-50% moisture content.
It sucks to see the water under the duct like that but at the same time it’s promising as it’s proving our theory of duct condensation being the culprit behind all of this damage.
You can mostly ignore my comment, I was just wondering if some of the condensation that was occurring outside above the roof was running down through a pinhole in the flashing and caulking. But it could have just been that so much water was trapped that space in between the roof layers that it pooled and/or was wicked back upwards. Since years of moisture damage could have slowly made the problem worse and compound as you say.
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Old 08-13-2020, 09:04 AM   #122
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


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You can mostly ignore my comment, I was just wondering if some of the condensation that was occurring outside above the roof was running down through a pinhole in the flashing and caulking. But it could have just been that so much water was trapped that space in between the roof layers that it pooled and/or was wicked back upwards. Since years of moisture damage could have slowly made the problem worse and compound as you say.
I suppose that is possible too. But if I had a pinhole, would it not be more problematic as when it rains that all of the water would be going in there?

Also, I was trying to figure this out, but what if there ARE pinholes in the flashing. what happens if water gets trapped in flashing? does it just evaporate over time?

Finally, yesterday was a pretty hot day. it was about 80 but extremely humid, so it felt like 90. however, it was cloudy and raining at times. That said, there was no dripping. Rust, I think you are on to something in regards to the "thermal expansion", because I don't think the roof temps were as hot, and as a result, the water volume probably did not expand enough for it to "drip".

I also used the thermal gun and did not spot any significant temp differentials in the supply duct like I had prior to insulating it, so that's good. Assuming that the primary source of the water was from the condensation, do you think it's wise to close up the ceiling in about a week of "drying"? I do want to continue my original bedroom renovation project, but the last thing I want is to close up all the ceilings, add insulation and then have the leak continue to happen.
Or do you guys think I should put some kind of drop ceiling in one of the areas, so I can continually check on it over time to confirm that the area is dry?
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Old 08-13-2020, 10:37 PM   #123
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


I agree, it probably was not a pinhole, since you have not seen it when raining. I was just thinking that the amount of water running down the side of the duct due to condensation was probably as much or more than what is found in a rainstorm, especially if the issue was at a point shaded by the overhead duct. Regardless the repair will take care of that.

I have no idea about the drying time. Or what mitigation is needed for wood that might have gotten wet but has not lost structural strength. There might be potential mold or mildew issues that you need to address.
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Old 08-13-2020, 11:04 PM   #124
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


If you get a few days with out dripping, what would have to happen to make it drip again. If water is trapped in the wood between sheets of roofing, it would need near 100% open on one side to dry out. Wood stored in water with out air is fine.

If the water is coming from above a layer of roofing, perhaps just sealing that from below. Running the AC more should help with the rest of the story.
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Old 08-21-2020, 10:10 PM   #125
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


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If you get a few days with out dripping, what would have to happen to make it drip again. If water is trapped in the wood between sheets of roofing, it would need near 100% open on one side to dry out. Wood stored in water with out air is fine.

If the water is coming from above a layer of roofing, perhaps just sealing that from below. Running the AC more should help with the rest of the story.
Hey guys, so it's been a week or so since I've insulated the main supply duct, and unfortunately, the renovation project had to proceed, so I had to close up some of the ceilings. I still get a little bit of dripping from the problem areas when it gets really hot and humid up top, usually when the temps are > 95F and humidity is > 85%, which is what I noticed.
Assuming that this is because the plywood trapped between the layers of roof is still wet, do you think if I stick one of these inline fans near the problematic layers and "pull" the air out and into my AC return if this will help speed up the drying process? Or do you think I should just route this ductwork out the window, or is this a bad idea? I just don't know where exactly the fan will pull air from if it's tightly sealed. I have been running a de-humidifier in the room with the dripping and im not sure if that has been helping too much.

Here's the inline fan I was thinking about:
https://www.acinfinity.com/hvac-home...roller-6-inch/
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Old 08-21-2020, 10:31 PM   #126
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


I could be wrong, but I don't think adding that fan will speed up the drying, as the water is encased and needs time to migrate and evaporate (assuming it is old water trapped above the plywood layer.). Really driving down the humidity or drilling holes to speed the process might help, but short of cutting open or replacing those boards I think it will take a long time.
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Old 08-22-2020, 12:09 AM   #127
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


Is it the combination of hot outside and AC that cause the dripping?
What would happen if you sealed it off so the water had no place to drip too. Just wet plywood stuck between to layers of roofing?
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Old 08-22-2020, 09:26 AM   #128
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Re: Troubleshooting 8 year old leak - possibly HVAC duct related


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Is it the combination of hot outside and AC that cause the dripping?
What would happen if you sealed it off so the water had no place to drip too. Just wet plywood stuck between to layers of roofing?
I think the source of the water that made the plywood wet was the AC condensation and perhaps some leaking from bad flashing in the past. Both of those issues have been mitigated. Therefore I think it's just residual water from the plywood "sandwiched" between two roofing layers that's wet and needs to dry out. unfortunately I don't know how much of the plywood has been water logged - if it's just the section in the master bedroom, or did it spread all throughout the roof - which would make the drying period much longer. currently I have closed up all the ceiling joists with insulation + sheetrock, with only the room near the main supply duct that is outfitted with a drop ceiling (so I can monitor some of the dripping + more venting)
Today is another hot day so I have a feeling it's going to drip again. Unfortunately I am probably going to have to tear out the roof from the top to be sure... I don't know if any other options... or wait it out and then run into the issue of having my sheetrock and ceiling tiles soaked over time.. I guess at least this time around I'll know when it's happening (instead of being fooled by the drip pan)
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