Condensation Issues with Flash and Batt Insulation
I got a big condensation problem at the moment and need any and all advice I can get.
Building a home in Southern MN. Zone 6. 2×6 wall cavity. 1/2 OBS sheeting on outside. 1.5″ closed cell foam R-10.5 and R13 unfaced fiberglass.
Inside is all rocked, and was on the last coat of mud, and we have had a cold snap over the last week bringing temps down to -10 or more. About 2 days into this cold snap on the coldest to date we noticed moisture at the bottom of the drywall between some stud cavities. This continued to get worse through out the day and in more locations.
House as being warmed to ~62 degrees, and sadly the humidity levels were around 60%. I cranked the temp to 70, and got two dehumidifiers going. I also didn’t have the house isolated from the garage at them time. Both were kept at the same temp. The following day I returned and Humidity was down to 52%. Condensation issues appeared the same or worse. I sealed the house off from the garage and today the humidity was down to 47%. I now have 2 more dehumidifiers (4 total) as I type this.
I had some exposed studs still and put fiberglass over them to see if things would condensate behind them, and although I’m not really seeing or feeling moister it feels borderline damp. I cut open 2 different spots in places that were wet, and to no surprise there was plenty of water at the bottom and the fiberglass was wet. (I cut about 3 inches up from the bottom).
We were very meticulous about caulking all framing, double, triple, top, bottom plates ect. Even caulked around ~1-4″ of each stud where the 1.5″ of foam stopped. So I really don’t think there is air leaks. Although I don’t see condensation or water at the bottom of each stud bay. That being said I got a good feeling if I cut into a dry one there would be.
This is my personal home. I’ve worked endlessly, and so has family. This obviously is very disheartening. I realize now I should of kept moisture levels under control without a doubt to start with, but I cant go back in time. I also now have concerns whether that would of been enough to begin with.
At this point here are my main questions that I’m hoping someone has stuck around long enough to answer.
1) What steps or suggestions should I immediately be doing. Example: Tomorrow morning do a, b, c, d, etc.
2) Is 1.5″ of closed cell enough for my zone and these temperatures?
3) If I had the RH in the house at 40% and walls painted. House at 70. Am I going to see these issues in the future with the setup I have. If we have cold snaps of -10 degree weeks?
4) I ask these questions because I understand or at least I think I do its because the temp of the foam is colder than the dew temp based on the RH and internal temp of the home. I’m also concerned because if I understand it correctly in theory with 70 degree interior temp and 35% RH I’m left with a dew point of 41 degrees and at 17 degrees outside the foam would reach 40.85 degrees which is less that the 41 degrees. I assume the drywall being painted helps helps reduce the amount of RH in the air in the wall cavity which further drops the dew point but I guess I dont know how much and its all got me extremely concerned at this point as anyone might imagine with it being my first home build and my own on top of it.
Thanks for taking the time to read everything. If you have any questions or important details that I overlooked please ask. I’ll respond asap.
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